1.
Yoke
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There are several types of yoke, used in different cultures, and for different types of oxen. A pair of oxen may be called a yoke of oxen, other animals that may be yoked include horses, mules, donkeys, and water buffalo. The word yoke is believed to derive from Proto-Indo-European *yugóm, from verb *yeug-, the verb to subjugate derives from the Latin form. A bow yoke /ˈboʊ/ is a shaped wooden crosspiece bound to the necks of a pair of oxen and it is held on the animals necks by an oxbow, from which it gets its name. The oxbow is usually U-shaped and also transmits force from the animals shoulders, a swivel between the animals, beneath the centre of the yoke, attaches to the pole of a vehicle or to chains used to drag a load. Bow yokes are traditional in Europe, and in the United States, Australia, a head yoke fits onto the head of the oxen. It usually fits behind the horns, and has carved-out sections into which the fit, it may be a single beam attached to both oxen, or each ox may have a separate short beam. The yoke is then strapped to the horns of the oxen with yoke straps, some types fit instead onto the front of the head, again strapped to the horns, and ox pads are then used for cushioning the forehead of the ox. A tug pole is held to the bottom of the yoke using yoke irons and chains, the tug pole can either be a short pole with a chain attached for hauling, or a long pole with a hook on the end that has no chain at all. Head yokes are used in southern Europe, much of South America. A withers yoke is a yoke that fits just in front of the withers, or the shoulder blades, of the oxen. The yoke is held in position by straps, either alone or with a pair of wooden staves either side of the oxs withers, withers yokes particularly suit zebu cattle, which have high humps on their withers. Withers yokes are used in Africa and India, where zebu cattle are common. Although all three types are effective, each has its advantages and disadvantages. As mentioned above, withers yokes suit zebu cattle, and head yokes can of course only be used for animals with suitable horns. A single-beam head yoke may offer better braking ability on downhill grades and appears to be preferred in rugged areas such as Switzerland, Spain. Bow yokes need to be the size for the animal, and new ones are often made as the animal grows. Whichever type is used, various lengths of yoke may be required for different agricultural implements or to adjust to different crop-row spacings, a yoke may be used with a single animal
2.
Chicken
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The chicken is a type of domesticated fowl, a subspecies of the red junglefowl. It is one of the most common and widespread domestic animals, humans keep chickens primarily as a source of food, consuming both their meat and their eggs. From India, the chicken was imported to Lydia in western Asia Minor. In the UK and Ireland adult male chickens over the age of one year are known as cocks, whereas in America, Australia. Males less than a year old are cockerels, females over a year old are known as hens and younger females as pullets although in the egg-laying industry, a pullet becomes a hen when she begins to lay eggs at 16 to 20 weeks of age. In Australia and New Zealand, there is a generic term chook /ˈtʃʊk/ to describe all ages, the young are called chicks and the meat is called chicken. Chicken originally referred to domestic fowl. The species as a whole was then called domestic fowl, or just fowl. This use of chicken survives in the phrase Hen and Chickens, sometimes used as a British public house or theatre name, the word chicken is sometimes erroneously construed to mean females exclusively, despite the term hen for females being in wide circulation. In the Deep South of the United States chickens are also referred to by the slang term yardbird, in the wild, they often scratch at the soil to search for seeds, insects and even animals as large as lizards, small snakes or young mice. Chickens may live for five to ten years, depending on the breed, the worlds oldest chicken was a hen which died of heart failure at the age of 16 according to Guinness World Records. However, in some breeds, such as the Sebright chicken, the rooster has only slightly pointed neck feathers, the identification can be made by looking at the comb, or eventually from the development of spurs on the males legs. Adult chickens have a fleshy crest on their heads called a comb, or cockscomb, collectively, these and other fleshy protuberances on the head and throat are called caruncles. Both the adult male and female have wattles and combs, a muff or beard is a mutation found in several chicken breeds which causes extra feathering under the chickens face, giving the appearance of a beard. Domestic chickens are not capable of long distance flight, although birds are generally capable of flying for short distances. Chickens may occasionally fly briefly to explore their surroundings, but generally do so only to flee perceived danger, Chickens are gregarious birds and live together in flocks. They have an approach to the incubation of eggs and raising of young. Individual chickens in a flock will dominate others, establishing an order, with dominant individuals having priority for food access
3.
Egg as food
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Eggs are laid by female animals of many different species, including birds, reptiles, amphibians, mammals, and fish, and have been eaten by humans for thousands of years. Bird and reptile eggs consist of an eggshell, albumen. The most popular choice for egg consumption are chicken eggs, other popular choices for egg consumption are duck, quail, roe, and caviar. Egg yolks and whole eggs store significant amounts of protein and choline, due to their protein content, the United States Department of Agriculture categorizes eggs as Meats within the Food Guide Pyramid. Despite the nutritional value of eggs, there are potential health issues arising from egg quality, storage. Chickens and other egg-laying creatures are widely kept throughout the world, in 2009, an estimated 62.1 million metric tons of eggs were produced worldwide from a total laying flock of approximately 6.4 billion hens. There are issues of variation in demand and expectation, as well as current debates concerning methods of mass production. In 2012, the European Union banned battery husbandry of chickens, bird eggs have been valuable foodstuffs since prehistory, in both hunting societies and more recent cultures where birds were domesticated. The chicken was probably domesticated for its eggs before 7500 BCE, chickens were brought to Sumer and Egypt by 1500 BCE, and arrived in Greece around 800 BCE, where the quail had been the primary source of eggs. In Thebes, Egypt, the tomb of Haremhab, built about 1420 BCE, shows a depiction of a man carrying bowls of ostrich eggs and other large eggs, presumably those of the pelican, as offerings. In ancient Rome, eggs were preserved using a number of methods, the Romans crushed the shells in their plates to prevent evil spirits from hiding there. In the Middle Ages, eggs were forbidden during Lent because of their richness, the word mayonnaise possibly was derived from moyeu, the medieval French word for the yolk, meaning center or hub. Egg scrambled with acidic fruit juices were popular in France in the 17th century, the dried egg industry developed in the 19th century, before the rise of the frozen egg industry. In 1878, a company in St. Louis, Missouri started to transform egg yolk and white into a light-brown, the production of dried eggs significantly expanded during World War II, for use by the United States Armed Forces and its allies. In 1911, the egg carton was invented by Joseph Coyle in Smithers, British Columbia, early egg cartons were made of paper. Bird eggs are a food and one of the most versatile ingredients used in cooking. They are important in many branches of the food industry. The most commonly used bird eggs are those from the chicken, duck and goose eggs, and smaller eggs, such as quail eggs, are occasionally used as a gourmet ingredient in western countries
4.
Egg
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An egg is the organic vessel containing the zygote in which an animal embryo develops until it can survive on its own, at which point the animal hatches. An egg results from fertilization of an ovum, most arthropods, vertebrates, and mollusks lay eggs, although some do not, such as scorpions and most mammals. Reptile eggs, bird eggs, and monotreme eggs are laid out of water, eggs laid on land or in nests are usually kept within a favorable temperature range while the embryo grows. When the embryo is developed it hatches, i. e. breaks out of the eggs shell. Some embryos have an egg tooth with which to crack, pip. The largest recorded egg is from a shark, and was 30 cm ×14 cm ×9 cm in size. At 1.5 kg and up to 17.8 cm ×14 cm, the bee hummingbird produces the smallest known bird egg, which weighs half of a gram. The eggs laid by some reptiles and most fish can be smaller. Reproductive structures similar to the egg in other kingdoms are termed spores, or in spermatophytes seeds, several major groups of animals typically have readily distinguishable eggs. The most common strategy for fish is known as oviparity. Typically large numbers of eggs are laid at one time and the eggs are left to develop without parental care. When the larvae hatch from the egg, they carry the remains of the yolk in a yolk sac which continues to nourish the larvae for a few days as they learn how to swim. Once the yolk is consumed, there is a point after which they must learn how to hunt. A few fish, notably the rays and most sharks use ovoviviparity in which the eggs are fertilized, however the larvae still grow inside the egg consuming the eggs yolk and without any direct nourishment from the mother. The mother then gives birth to relatively mature young, in certain instances, the physically most developed offspring will devour its smaller siblings for further nutrition while still within the mothers body. This is known as intrauterine cannibalism, the eggs of fish and amphibians are jellylike. Cartilagenous fish eggs are fertilized internally and exhibit a variety of both internal and external embryonic development. Most fish species spawn eggs that are fertilized externally, typically with the male inseminating the eggs after the female lays them and these eggs do not have a shell and would dry out in the air
5.
Embryo
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An embryo is an early stage of development of a multicellular diploid eukaryotic organism. In general, in organisms that reproduce sexually, an embryo develops from a zygote, the zygote possesses half the DNA of each of its two parents. In plants, animals, and some protists, the zygote will begin to divide by mitosis to produce a multicellular organism, the result of this process is an embryo. First attested in English in the mid-14c, the word embryon derives from Medieval Latin embryo, itself from Greek ἔμβρυον, lit. Young one, which is the neuter of ἔμβρυος, lit, growing in, from ἐν, in and βρύω, swell, be full, the proper Latinized form of the Greek term would be embryum. In animals, the development of the zygote into an embryo proceeds through specific stages of blastula, gastrula. The blastula stage typically features a fluid-filled cavity, the blastocoel, surrounded by a sphere or sheet of cells, in a placental mammal, an ovum is fertilized in a fallopian tube through which it travels into the uterus. An embryo is called a fetus at an advanced stage of development. In humans, this is from the week of gestation. During gastrulation the cells of the blastula undergo coordinated processes of cell division, invasion, in triploblastic organisms, the three germ layers are called endoderm, ectoderm, and mesoderm. The position and arrangement of the layers are highly species-specific, however. For example, in neurogenesis, a subpopulation of cells is set aside to become the brain, spinal cord. Modern developmental biology is extensively probing the molecular basis for every type of organogenesis, including angiogenesis, chondrogenesis, myogenesis, osteogenesis, and many others. In botany, a plant embryo is part of a seed, consisting of precursor tissues for the leaves, stem. Once the embryo begins to germinate — grow out from the seed — it is called a seedling, bryophytes and ferns also produce an embryo, but do not produce seeds. In these plants, the embryo begins its existence attached to the inside of the archegonium on a parental gametophyte from which the egg cell was generated, the structure and development of the rest of the embryo varies by group of plants. Once the embryo has expanded beyond the enclosing archegonium, it is no longer termed an embryo, embryos are used in various fields of research and in techniques of assisted reproductive technology. An egg may be fertilized in vitro and the embryo may be frozen for later use
6.
Parasitoid
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A parasitoid is an organism that spends a significant portion of its life history attached to or within a single host organism in a relationship where the host is ultimately killed. Thus, parasitoidy is an evolutionary strategy to typical parasitism. There are parasitoids in a variety of taxa, including microbial diseases, plants, crustaceans, insects. Especially among the Hymenoptera, ichneumons and many wasps are highly specialised for a way of life. Some parasitoidal wasps are used in biological pest control, the term parasitoid was coined in 1913 by the Swedo-Finnish writer Odo Morannal Reuter, and adopted in English by his reviewer, William Morton Wheeler. Reuter used it to describe the strategy where the parasite develops in or on the body of a single host individual, eventually killing that host, since that time, the concept has been variously generalised and widely applied. These are adaptive peaks, with possible intermediate strategies. Parasitoids eventually kill their host, typically before it can produce offspring, a nonlethal parasitic organism, especially if it is a fungus, is sometimes termed a biotroph, while a parasitoidal fungus may be called a necrotroph. Idiobiont parasitoids prevent further development of the host after initially immobilizing it, koinobiont parasitoids allow the host to continue its development while feeding upon it, and may parasitise any host life stage. There is no separation between conventional parasitism and parasitoidy. For example, blood-sucking mites sometimes overwhelm nestlings of birds such as swallows to the point that the birds cannot fledge successfully. At the opposite extreme, parasitoidy grades into predation, differences between various hunting wasps provide convenient illustrations. Predatory social wasps hunt flies, caterpillars and the like, grab them, butcher them, carry them home and feed them to their young. Similarly, some solitary wasps such as beewolves, sting prey, sometimes fatally, before saving it, usually entire, in contrast, the best-known protelean solitary hunting wasps sting prey to paralyse it before storing it for the young in the nest. Other wasps paralyse prey in the plant or other environment in which it feeds, before laying eggs nearby, some insect parasitoids lay their eggs where the larvae must locate the prey for themselves when they hatch from the eggs. Examples include flies in the families Tachinidae and Bombyliidae, often with sophisticated physiological, in another strategy, some parasitoids influence the hosts behaviour in ways that favour the propagation of the parasitoid, often at the cost of the hosts life. Similarly, as strepsipteran parasitoids of ants mature, they cause the hosts to climb high on grass stalks, positions that are risky, but favour the emergence of the strepsipterans. Other species of endoparasitoids cause infected woodlice and land Amphipoda such as Talitroides to run about in the open by day, the rabies virus affects the hosts central nervous system, eventually killing it, but perhaps helping to disseminate the virus by modifying the hosts behaviour
7.
Placenta
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The placenta provides oxygen and nutrients to growing babies and removes waste products from the babys blood. The placenta attaches to the wall of the uterus, and the umbilical cord develops from the placenta. The umbilical cord is what connects the mother and the baby, Placentas are a defining characteristic of placental mammals, but are also found in some non-mammals with varying levels of development. The homology of structures in various viviparous organisms is debatable. The classical plural is placentae, but the form placentas is common in modern English, prototherial and metatherial mammals produce a choriovitelline placenta that, while connected to the uterine wall, provides nutrients mainly derived from the egg sac. In humans, the placenta averages 22 cm in length and 2–2.5 cm in thickness, with the center being the thickest, and it typically weighs approximately 500 grams. It has a dark reddish-blue or crimson color and it connects to the fetus by an umbilical cord of approximately 55–60 cm in length, which contains two umbilical arteries and one umbilical vein. The umbilical cord inserts into the chorionic plate, vessels branch out over the surface of the placenta and further divide to form a network covered by a thin layer of cells. This results in the formation of villous tree structures, on the maternal side, these villous tree structures are grouped into lobules called cotyledons. In humans, the placenta usually has a shape. The placental flora more closely resembles that of the oral microbiome than either the vaginal or rectal microbiome, in non-human animals, part of the microbiome is passed onto offspring even before the offspring are born. Bacteriologists assume that the same holds true for humans. The placenta begins to develop upon implantation of the blastocyst into the maternal endometrium, the outer layer of the blastocyst becomes the trophoblast, which forms the outer layer of the placenta. This outer layer is divided into two layers, the underlying cytotrophoblast layer and the overlying syncytiotrophoblast layer. The syncytiotrophoblast is a continuous cell layer that covers the surface of the placenta. It forms as a result of differentiation and fusion of the underlying cytotrophoblast cells, the syncytiotrophoblast, thereby contributes to the barrier function of the placenta. Development of the blood supply to the placenta is complete by the end of the first trimester of pregnancy. In preparation for implantation of the blastocyst, the uterine endometrium undergoes decidualisation, spiral arteries in decidua are remodeled so that they become less convoluted and their diameter is increased
8.
Reproductive system
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The reproductive system or genital system is a system of sex organs within an organism which work together for the purpose of sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are also important accessories to the reproductive system, unlike most organ systems, the sexes of differentiated species often have significant differences. These differences allow for a combination of material between two individuals, which allows for the possibility of greater genetic fitness of the offspring. In mammals, the organs of the reproductive system include the external genitalia as well as a number of internal organs including the gamete producing gonads. Diseases of the reproductive system are very common and widespread. Most other vertebrate animals have generally similar reproductive systems consisting of gonads, ducts, however, there is a great diversity of physical adaptations as well as reproductive strategies in every group of vertebrates. Vertebrate animals all share key elements of their reproductive systems and they all have gamete-producing organs or gonads. In females, these gonads are then connected by oviducts to an opening to the outside of the body, typically the cloaca, the human reproductive system usually involves internal fertilization by sexual intercourse. During this process, the male inserts his penis into the females vagina and ejaculates semen. The sperm then travels through the vagina and cervix into the uterus or fallopian tubes for fertilization of the ovum, upon successful fertilization and implantation, gestation of the fetus then occurs within the females uterus for approximately nine months, this process is known as pregnancy in humans. Gestation ends with birth, the process of birth is known as labor, labor consists of the muscles of the uterus contracting, the cervix dilating, and the baby passing out the vagina. Humans babies and children are nearly helpless and require high levels of care for many years. One important type of care is the use of the mammary glands in the female breasts to nurse the baby. The female reproductive system has two functions, The first is to produce egg cells, and the second is to protect, the male reproductive system has one function, and it is to produce and deposit sperm. Humans have a level of sexual differentiation. In addition to differences in nearly every organ, numerous differences typically occur in secondary sexual characteristics. The male reproductive system is a series of organs located outside of the body, the primary direct function of the male reproductive system is to provide the male sperm for fertilization of the ovum. The major reproductive organs of the male can be grouped into three categories, the first category is sperm production and storage
9.
Invertebrate
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Invertebrates are animals that neither possess nor develop a vertebral column, derived from the notochord. This includes all animals apart from the subphylum Vertebrata, familiar examples of invertebrates include insects, crabs, lobsters and their kin, snails, clams, octopuses and their kin, starfish, sea-urchins and their kin, jellyfish, and worms. The majority of species are invertebrates, one estimate puts the figure at 97%. Many invertebrate taxa have a number and variety of species than the entire subphylum of Vertebrata. Some of the invertebrates, such as the Tunicata and Cephalochordata are more closely related to the vertebrates than to other invertebrates. This makes the term invertebrate paraphyletic and hence almost meaningless for taxonomic purposes, the word invertebrate comes from the form of the Latin word vertebra, which means a joint in general, and sometimes specifically a joint from the spinal column of a vertebrate. In turn the jointed aspect of vertebra derived from the concept of turning, coupled with the prefix in-, meaning not or without. The term invertebrates is not always precise among non-biologists since it does not accurately describe a taxon in the way that Arthropoda. Each of these describes an valid taxon, phylum, subphylum or family. Invertebrata is a term of convenience, not a taxon, it has very little circumscriptional significance except within the Chordata, the Vertebrata as a subphylum comprises such a small proportion of the Metazoa that to speak of the kingdom Animalia in terms of Vertebrata and Invertebrata has limited practicality. That would at least circumscribe the Chordata, however, even the notochord would be a less fundamental criterion than aspects of embryological development and symmetry or perhaps bauplan. The following text reflects earlier scientific understanding of the term and of animals which have constituted it. According to this understanding, invertebrates do not possess a skeleton of bone and they include hugely varied body plans. Many have fluid-filled, hydrostatic skeletons, like jellyfish or worms, others have hard exoskeletons, outer shells like those of insects and crustaceans. The most familiar invertebrates include the Protozoa, Porifera, Coelenterata, Platyhelminthes, Nematoda, Annelida, Echinodermata, Mollusca, Arthropoda include insects, crustaceans and arachnids. By far the largest number of described species are insects. The following table lists the number of described extant species for major invertebrate groups as estimated in the IUCN Red List of Threatened Species,2014.3. The IUCN estimates that 66,178 extant vertebrate species have been described, the trait that is common to all invertebrates is the absence of a vertebral column, this creates a distinction between invertebrates and vertebrates
10.
Egg cell
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The egg cell, or ovum, is the female reproductive cell in oogamous organisms. The egg cell is not capable of active movement. When egg and sperm fuse, a cell is formed. Karl Ernst von Baer discovered the mammalian ovum in 1827, the fusion of spermatozoa with ova was observed by Oskar Hertwig in 1876. In animals, egg cells are known as ova. The term ovule is used for the young ovum of an animal, in vertebrates, ova are produced by female gonads called ovaries a number of ova are present at birth in mammals and mature via oogenesis. White et al. disproved the longstanding dogma that all of the ova are produced before birth, the team from the Vincent Center for Reproductive Biology, Massachusetts, Boston could prove that oocyte fromation takes place in ovaries of reproductive-age women. This report challenged a fundamental belief, held since the 1950s, in all mammals the ovum is fertilized inside the female body. The human ova grow from primitive germ cells that are embedded in the substance of the ovaries, each of them divides repeatedly to give secretions of the uterine glands, ultimately forming a blastocyst. The ovum is one of the largest cells in the human body, the human ovum measures approximately 0.12 mm in diameter. Ooplasm is the yolk of the ovum, a substance at its center, which contains its nucleus, named the germinal vesicle. Mammalian ova contain only an amount of the nutritive yolk. In contrast, bird eggs contain enough to supply the chick with nutriment throughout the period of incubation. In the oviparous animals the ova develop protective layers and pass through the oviduct to the outside of the body and they are fertilized by male sperm either inside the female body, or outside. After fertilization, an embryo develops, nourished by nutrients contained in the egg and it then hatches from the egg, outside the mothers body. See egg for a discussion of eggs of oviparous animals, the egg cells cytoplasm and mitochondria are the sole means the egg is able to reproduce by mitosis and eventually form a blastocyst after fertilization. Some fish, reptiles and many use this technique. Nearly all land plants have alternating diploid and haploid generations, gametes are produced by the gametophyte, which is the haploid generation
11.
Lipid
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In biology, lipids comprise a group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins, monoglycerides, diglycerides, triglycerides, phospholipids, and others. The main biological functions of lipids include storing energy, signaling, lipids have applications in the cosmetic and food industries as well as in nanotechnology. Biological lipids originate entirely or in part from two types of biochemical subunits or building-blocks, ketoacyl and isoprene groups. Although the term lipid is sometimes used as a synonym for fats, fats are a subgroup of lipids called triglycerides, lipids also encompass molecules such as fatty acids and their derivatives, as well as other sterol-containing metabolites such as cholesterol. Although humans and other mammals use various biosynthetic pathways both to break down and to synthesize lipids, some essential lipids cannot be made this way, the word lipid stems etymologically from the Greek lipos. The fatty acid structure is one of the most fundamental categories of biological lipids, the carbon chain, typically between four and 24 carbons long, may be saturated or unsaturated, and may be attached to functional groups containing oxygen, halogens, nitrogen, and sulfur. If a fatty acid contains a double bond, there is the possibility of either a cis or trans geometric isomerism, cis-double bonds cause the fatty acid chain to bend, an effect that is compounded with more double bonds in the chain. This in turn plays an important role in the structure and function of cell membranes, most naturally occurring fatty acids are of the cis configuration, although the trans form does exist in some natural and partially hydrogenated fats and oils. Examples of biologically important fatty acids include the eicosanoids, derived primarily from arachidonic acid and eicosapentaenoic acid, that include prostaglandins, leukotrienes, docosahexaenoic acid is also important in biological systems, particularly with respect to sight. Other major lipid classes in the fatty acid category are the fatty esters, fatty esters include important biochemical intermediates such as wax esters, fatty acid thioester coenzyme A derivatives, fatty acid thioester ACP derivatives and fatty acid carnitines. The fatty amides include N-acyl ethanolamines, such as the cannabinoid neurotransmitter anandamide, glycerolipids are composed of mono-, di-, and tri-substituted glycerols, the best-known being the fatty acid triesters of glycerol, called triglycerides. The word triacylglycerol is sometimes used synonymously with triglyceride, in these compounds, the three hydroxyl groups of glycerol are each esterified, typically by different fatty acids. Because they function as a store, these lipids comprise the bulk of storage fat in animal tissues. The hydrolysis of the bonds of triglycerides and the release of glycerol. Additional subclasses of glycerolipids are represented by glycosylglycerols, which are characterized by the presence of one or more sugar residues attached to glycerol via a glycosidic linkage, examples of structures in this category are the digalactosyldiacylglycerols found in plant membranes and seminolipid from mammalian sperm cells. Glycerophospholipids, usually referred to as phospholipids, are ubiquitous in nature and are key components of the bilayer of cells, as well as being involved in metabolism. Neural tissue contains high amounts of glycerophospholipids, and alterations in their composition has been implicated in various neurological disorders. Examples of glycerophospholipids found in biological membranes are phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine, the major sphingoid base of mammals is commonly referred to as sphingosine
12.
Oogenesis
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Oogenesis, ovogenesis, or oögenesis /ˌoʊ. əˈdʒɛnᵻsɪs/ is the differentiation of the ovum into a cell competent to further development when fertilized. It is developed from the oocyte by maturation. In mammals, the first part of oogenesis starts in the epithelium, which gives rise to the development of ovarian follicles. Oogenesis consists of several sub-processes, oocytogenesis, ootidogenesis, and finally maturation to form an ovum, folliculogenesis is a separate sub-process that accompanies and supports all three oogenetic sub-processes. Oogenesis starts with the process of developing oogonia, which occurs via the transformation of primordial follicles into primary oocytes, oocytogenesis is complete either before or shortly after birth. Recently, however, two publications have challenged the belief that a number of oocytes are set around the time of birth. The renewal of ovarian follicles from germline stem cells has been reported in the postnatal mouse ovary, in contrast, DNA clock measurements do not indicate ongoing oogenesis during human females lifetimes. Thus, further experiments are required to determine the dynamics of small follicle formation. The succeeding phase of ootidogenesis occurs when the primary oocyte develops into an ootid and this is achieved by the process of meiosis. In fact, a primary oocyte is, by its biological definition, however, although this process begins at prenatal age, it stops at prophase I. In late fetal life, all oocytes, still primary oocytes, have halted at this stage of development, after menarche, these cells then continue to develop, although only a few do so every menstrual cycle. Meiosis I of ootidogenesis begins during embryonic development, but halts in the stage of prophase I until puberty. The mouse oocyte in the stage actively repairs DNA damage. For those primary oocytes that continue to develop in each cycle, however, synapsis occurs and tetrads form. As a result of meiosis I, the oocyte has now developed into the secondary oocyte. Immediately after meiosis I, the secondary oocyte initiates meiosis II. However, this process is halted at the metaphase II stage until fertilization. When meiosis II has completed, an ootid and another polar body have now been created, synchronously with ootidogenesis, the ovarian follicle surrounding the ootid has developed from a primordial follicle to a preovulatory one
13.
Biosynthesis
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Biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds and this process often consists of metabolic pathways. Some of these pathways are located within a single cellular organelle, while others involve enzymes that are located within multiple cellular organelles. Examples of these pathways include the production of lipid membrane components. The prerequisite elements for biosynthesis include, precursor compounds, chemical energy and these elements create monomers, the building blocks for macromolecules. Biosynthesis occurs due to a series of chemical reactions, for these reactions to take place, the following elements are necessary, Precursor compounds, these compounds are the starting molecules or substrates in a reaction. These may also be viewed as the reactants in a chemical process. Chemical energy, chemical energy can be found in the form of high energy molecules and these molecules are required for energetically unfavorable reactions. Furthermore, the hydrolysis of these compounds drives a reaction forward, high energy molecules, such as ATP, have three phosphates. Often, the phosphate is split off during hydrolysis and transferred to another molecule. Catalytic enzymes, these molecules are special proteins that catalyze a reaction by increasing the rate of the reaction, coenzymes or cofactors, cofactors are molecules that assist in chemical reactions. These may be metal ions, vitamin derivatives such as NADH and acetyl CoA, in the case of NADH, the molecule transfers a hydrogen, whereas acetyl CoA transfers an acetyl group, and ATP transfers a phosphate. Two examples of type of reaction occur during the formation of nucleic acids. For some of these steps, chemical energy is required, Precursor molecule + ATP ↽ − − ⇀ product AMP + PP i Simple compounds that are converted into other compounds with the assistance of cofactors. For example, the synthesis of phospholipids requires acetyl CoA, while the synthesis of another component, shingolipids. The general equation for these examples is, Precursor molecule + Cofactor → e n z y m e macromolecule Simple compounds that join together to create a macromolecule, for example, fatty acids join together to form phopspholipids. In turn, phospholipids and cholesterol interact noncovalently in order to form the lipid bilayer and this reaction may be depicted as follows, Molecule 1 + Molecule 2 ⟶ macromolecule Many intricate macromolecules are synthesized in a pattern of simple, repeated structures. For example, the simplest structures of lipids are fatty acids, fatty acids are hydrocarbon derivatives, they contain a carboxyl group “head” and a hydrocarbon chain “tail. ”These fatty acids create larger components, which in turn incorporate noncovalent interactions to form the lipid bilayer
14.
Algae
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Algae is an informal term for a large, diverse group of photosynthetic organisms which are not necessarily closely related, and is thus polyphyletic. Included organisms range from unicellular genera, such as Chlorella and the diatoms, to forms, such as the giant kelp. Most are aquatic and autotrophic and lack many of the cell and tissue types, such as stomata, xylem, and phloem. No definition of algae is generally accepted, one definition is that algae have chlorophyll as their primary photosynthetic pigment and lack a sterile covering of cells around their reproductive cells. Some authors exclude all prokaryotes thus do not consider cyanobacteria as algae, Algae constitute a polyphyletic group since they do not include a common ancestor, and although their plastids seem to have a single origin, from cyanobacteria, they were acquired in different ways. Green algae are examples of algae that have primary chloroplasts derived from endosymbiotic cyanobacteria, diatoms and brown algae are examples of algae with secondary chloroplasts derived from an endosymbiotic red alga. Algae exhibit a range of reproductive strategies, from simple asexual cell division to complex forms of sexual reproduction. Algae lack the various structures that characterize land plants, such as the phyllids of bryophytes, rhizoids in nonvascular plants, and the roots, leaves, and other organs found in tracheophytes. Most are phototrophic, although some are mixotrophic, deriving energy both from photosynthesis and uptake of organic carbon either by osmotrophy, myzotrophy, or phagotrophy. Some other heterotrophic organisms, such as the apicomplexans, are derived from cells whose ancestors possessed plastids. Fossilized filamentous algae from the Vindhya basin have been dated back to 1.6 to 1.7 billion years ago, the singular alga is the Latin word for seaweed and retains that meaning in English. Although some speculate that it is related to Latin algēre, be cold, a more likely source is alliga, binding, entwining. The Ancient Greek word for seaweed was φῦκος, which could mean either the seaweed or a red dye derived from it, the Latinization, fūcus, meant primarily the cosmetic rouge. It could be any color, black, red, green, accordingly, the modern study of marine and freshwater algae is called either phycology or algology, depending on whether the Greek or Latin root is used. The name Fucus appears in a number of taxa, most algae contain chloroplasts that are similar in structure to cyanobacteria. Chloroplasts contain circular DNA like that in cyanobacteria and presumably represent reduced endosymbiotic cyanobacteria, however, the exact origin of the chloroplasts is different among separate lineages of algae, reflecting their acquisition during different endosymbiotic events. The table below describes the composition of the three groups of algae. Their lineage relationships are shown in the figure in the upper right, many of these groups contain some members that are no longer photosynthetic
15.
Oogamy
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Oogamy is the familiar form of sexual reproduction. It is a form of anisogamy in which the female gamete is larger than the male gamete and is non-motile. The male gametes are typically highly motile to the zygote, oogamy predominantly occurs in animals, but can also be found in many protists, certain orders of algae, and some plants such as bryophytes, ferns, and some gymnosperms like cycads and ginkgo. In some algae, most gymnosperms and all angiosperms, a variation of oogamy occurs where the cells are non-motile as well. It appears that isogamy was the first stage of sexual reproduction, in several lineages, this form of reproduction independently evolved to anisogamy with gametes of male and female types to oogamy. There is an argument that this pattern was driven by the physical constraints on the mechanisms by which two gametes get together as required for sexual reproduction
16.
Gymnosperm
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The gymnosperms are a group of seed-producing plants that includes conifers, cycads, Ginkgo, and gnetophytes. The term gymnosperm comes from the Greek composite word γυμνόσπερμος, meaning naked seeds and their naked condition stands in contrast to the seeds and ovules of flowering plants, which are enclosed within an ovary. Gymnosperm seeds develop either on the surface of scales or leaves, often modified to form cones, the gymnosperms and angiosperms together compose the spermatophytes or seed plants. By far the largest group of living gymnosperms are the conifers, followed by cycads, gnetophytes, in early classification schemes, the gymnosperms were regarded as a natural group. There is conflicting evidence on the question of whether the living gymnosperms form a clade, for the most recent classification on extant gymnosperms see Christenhusz et al. There are 12 families,83 known genera with a total of ca 1080 known species, subclass Cycadidae Order Cycadales Family Cycadaceae, Cycas Family Zamiaceae, Dioon, Bowenia, Macrozamia, Lepidozamia, Encephalartos, Stangeria, Ceratozamia, Microcycas, Zamia. It is widely accepted that the gymnosperms originated in the late Carboniferous period and this appears to have been the result of a whole genome duplication event around 319 million years ago. Early characteristics of seed plants were evident in fossil progymnosperms of the late Devonian period around 383 million years ago, the scorpionflies likely engaged in pollination mutualisms with gymnosperms, long before the similar and independent coevolution of nectar-feeding insects on angiosperms. Evidence has also found that mid-Mesozoic gymnosperms were pollinated by Kalligrammatid lacewings. Conifers are by far the most abundant extant group of gymnosperms with six to eight families, with a total of 65-70 genera, conifers are woody plants and most are evergreens. The leaves of many conifers are long, thin and needle-like, other species, including most Cupressaceae and some Podocarpaceae, have flat, agathis in Araucariaceae and Nageia in Podocarpaceae have broad, flat strap-shaped leaves. Cycads are the next most abundant group of gymnosperms, with two or three families,11 genera, and approximately 338 species, the other extant groups are the 95-100 species of Gnetales and one species of Ginkgo. Pine, fir, spruce, and cedar are all examples of conifers that are used for lumber, some other common uses for gymnosperms are soap, varnish, nail polish, food, gum, and perfumes. Gymnosperms, like all plants, have a sporophyte-dominant life cycle. Two spore types, microspores and megaspores, are produced in pollen cones or ovulate cones. Gametophytes, as with all plants, develop within the spore wall. Pollen grains mature from microspores, and ultimately produce sperm cells, megagametophytes develop from megaspores and are retained within the ovule. During pollination, pollen grains are transferred between plants, from pollen cone to the ovule, being transferred by wind or insects
17.
Gametophyte
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A gametophyte is a stage in the life cycle of plants and algae that undergo alternation of generations. It is a multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte is the phase in the life cycle of plants. It develops sex organs that produce gametes, haploid sex cells that participate in fertilization to form a diploid zygote in which each cell has two sets of chromosomes. Cell division of the results in a new diploid multicellular organism, the second stage in the life cycle known as the sporophyte. In some multicellular green algae, red algae and brown algae sporophytes and gametophytes may be externally indistinguishable, in Ulva the gametes are isogamous, all of one size, shape and general morphology. In land plants, anisogamy is universal, as in animals, female and male gametes are called, respectively, eggs and sperm. Either the sporophyte or the gametophyte may be reduced, in bryophytes, the gametophyte is the most visible stage of the life cycle. The bryophyte gametophyte is longer lived, nutritionally independent, and the sporophytes are typically attached to the gametophytes, when a moss spore germinates it grows to produce a filament of cells. The mature gametophyte of mosses develops into leafy shoots that produce sex organs that produce gametes, eggs develop in archegonia and sperm in antheridia. In some bryophyte groups such as many liverworts of the order Marchantiales, in most ferns, gametophyte is a photosynthetic free living organism called a prothallus. However, in groups, notably the clade that includes Ophioglossaceae and Psilotaceae. Extant lycophytes produce several different types of gametophytes, in the families Lycopodiaceae and Huperziaceae, gametophytes are subterranean and mycotrophic, deriving nutrients from symbiosis with fungi. The gametophytes of Isoetes appear to be similar in respect to those of the extinct Carboniferous giant arborescent clubmosses, Lepidodendron. By contrast, in seed plants, gametophytes develop into multicellular organisms while still enclosed within the sporangium, vascular plants that produce only one type of spore are said to be homosporous. They have exosporic gametophytes—that is, the gametophyte is free-living and develops outside of the spore wall, exosporic gametophytes are normally bisexual, capable of producing both sperm and eggs. In heterosporous vascular plants, the gametophyte develops endosporically, within the spore wall and these gametophytes are unisexual, producing either sperm or eggs but not both. All vascular plants are dominant, and a trend toward smaller
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Flowering plant
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The flowering plants, also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants, with 416 families, approx. 13,164 known genera and a total of c.295,383 known species, etymologically, angiosperm means a plant that produces seeds within an enclosure, in other words, a fruiting plant. The term angiosperm comes from the Greek composite word meaning enclosed seeds, the ancestors of flowering plants diverged from gymnosperms in the Triassic Period, during the range 245 to 202 million years ago, and the first flowering plants are known from 160 mya. They diversified extensively during the Lower Cretaceous, became widespread by 120 mya, angiosperms differ from other seed plants in several ways, described in the table. These distinguishing characteristics taken together have made the angiosperms the most diverse and numerous land plants, the amount and complexity of tissue-formation in flowering plants exceeds that of gymnosperms. The vascular bundles of the stem are arranged such that the xylem and phloem form concentric rings, in the dicotyledons, the bundles in the very young stem are arranged in an open ring, separating a central pith from an outer cortex. In each bundle, separating the xylem and phloem, is a layer of meristem or active formative tissue known as cambium, the soft phloem becomes crushed, but the hard wood persists and forms the bulk of the stem and branches of the woody perennial. Among the monocotyledons, the bundles are more numerous in the stem and are scattered through the ground tissue. They contain no cambium and once formed the stem increases in diameter only in exceptional cases, the characteristic feature of angiosperms is the flower. Flowers show remarkable variation in form and elaboration, and provide the most trustworthy external characteristics for establishing relationships among angiosperm species, the function of the flower is to ensure fertilization of the ovule and development of fruit containing seeds. The floral apparatus may arise terminally on a shoot or from the axil of a leaf, occasionally, as in violets, a flower arises singly in the axil of an ordinary foliage-leaf. There are two kinds of cells produced by flowers. Microspores, which divide to become pollen grains, are the male cells and are borne in the stamens. The female cells called megaspores, which divide to become the egg cell, are contained in the ovule. The flower may consist only of parts, as in willow. Usually, other structures are present and serve to protect the sporophylls, the individual members of these surrounding structures are known as sepals and petals. The outer series is usually green and leaf-like, and functions to protect the rest of the flower, the inner series is, in general, white or brightly colored, and is more delicate in structure. It functions to attract insect or bird pollinators, attraction is effected by color, scent, and nectar, which may be secreted in some part of the flower
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Endosperm
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Endosperm is a tissue produced inside the seeds of most of the flowering plants following fertilization. It surrounds the embryo and provides nutrition in the form of starch, though it can also contain oils and this can make endosperm a source of nutrition in the human diet. For example, wheat endosperm is ground into flour for bread, other examples of endosperm that forms the bulk of the edible portion are coconut meat and coconut water, and corn. Some plants, such as orchids, lack endosperm in their seeds, in more derived flowering plants the embryo occupies most of the seed and the endosperm is non developed or consumed before the seed matures. Endosperm is formed when the two sperm nuclei inside a pollen grain reach the interior of a female gametophyte, one sperm nucleus fertilizes the egg cell, forming a zygote, while the other sperm nucleus usually fuses with the binucleate central cell, forming a primary endosperm cell. That cell created in the process of double fertilization develops into the endosperm, because it is formed by a separate fertilization, the endosperm constitutes an organism separate from the growing embryo. About 70% of angiosperm species have endosperm cells that are polyploid and these are typically triploid, but can vary widely from diploid to 15n. One species of flowering plant, Nuphar polysepala, has endosperm that is diploid, resulting from the fusion of a nucleus with one. There are three types of Endosperm development, Nuclear endosperm formation - where repeated free-nuclear divisions take place, commonly referred to as liquid endosperm. Coconut water is an example of this, cellular endosperm formation - where a cell-wall formation is coincident with nuclear divisions. Acoraceae has cellular endosperm development while other monocots are helobial, the evolutionary origins of double fertilization and endosperm are unclear, attracting researcher attention for over a century. There are the two hypotheses, The double fertilization initially used to produce two identical, independent embryos. Later these embryos acquired different roles, one growing into the mature organism, thus the early endosperm was probably diploid, like the embryo. Some gymnosperms, such as Ephedra, may produce twin embryos by double fertilization, either of these two embryos is capable of filling in the seed, but normally only one develops further. Also, most basal angiosperms still contain the embryo sac. Endosperm is the remnant of the actual gametophyte, similar to the complex multicellular gametophytes found in gymnosperms. In this case, acquisition of the nucleus from the sperm cell is a later evolutionary step. This nucleus may provide the organism with some control over endosperm development
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Egg white
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Albumen is the name for the clear liquid contained within an egg. In chickens it is formed from the layers of secretions of the section of the hens oviduct during the passage of the egg. It forms around fertilized or unfertilized egg yolks, the primary natural purpose of egg white is to protect the yolk and provide additional nutrition for the growth of the embryo. Egg white consists primarily of about 90% water into which is dissolved about 10% proteins, unlike the yolk, which is high in lipids, egg white contains almost no fat, and carbohydrate content is less than 1%. Egg whites contain just over 50% of the protein in the egg, Egg white has many uses in food and also many other uses. Egg white makes up around two-thirds of an egg by weight. Water constitutes about 90% of this, with protein, trace minerals, fatty material, vitamins, and glucose contributing the remainder. A raw U. S. large egg contains around 33 grams of egg white with 3.6 grams of protein,0.24 grams of carbohydrate and 55 milligrams of sodium and it contains no cholesterol and the energy content is about 17 Calories. Egg white is a solution and contains around 148 proteins. The table below lists the major proteins in egg whites by percentage, ovalbumin is the most abundant protein in albumen. Classed as phosphoglycoprotein, during storage, it converts into s-ovalbumin, Denaturation temperature is around 84°C, but it can be easily denatured by physical stresses. Conalbumin/ovotransferrin is a glycoprotein which has the capacity to bind the bi-, at its isoelectric pH, it can bind two cations and assume a red or yellow color. These metal complexes are more stable than the native state. Ovomucoid is the major allergen from egg white and is a heat-resistant glycoprotein found to be a trypsin inhibitor, ovomucin is a glycoprotein which may contribute to the gel-like structure of thick albumen. The amount of ovomucin in the thick albumen is four times greater than in the thin albumen, the physical stress of beating egg whites can create a foam. Two types of stress are caused by beating them with a whisk. The second stress comes from the mixing of air into the whites, when beating egg whites, they are classified in three stages according to the peaks they form when the beater is lifted, soft, firm, and stiff peaks. Overbeaten eggs take on a dry appearance, and eventually collapse, Egg whites do not beat up correctly if they are exposed to any form of fat, such as cooking oils or the fats contained in egg yolk
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Cell membrane
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The cell membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is permeable to ions and organic molecules and controls the movement of substances in. The basic function of the membrane is to protect the cell from its surroundings. It consists of the bilayer with embedded proteins. Cell membranes can be artificially reassembled, Some authors that did not believe that there was a functional permeable boundary at the surface of the cell preferred to use the term plasmalemma to the extern region of the cell. The cell membrane surrounds the cytoplasm of living cells, physically separating the components from the extracellular environment. The cell membrane also plays a role in anchoring the cytoskeleton to provide shape to the cell, fungi, bacteria, most archaea, and plants also have a cell wall, which provides a mechanical support to the cell and precludes the passage of larger molecules. The cell membrane is permeable and able to regulate what enters and exits the cell. The movement of substances across the membrane can be passive, occurring without the input of cellular energy, or active. The membrane also maintains the cell potential, the cell membrane thus works as a selective filter that allows only certain things to come inside or go outside the cell. The cell employs a number of mechanisms that involve biological membranes,1. Passive osmosis and diffusion, Some substances such as carbon dioxide and oxygen, can move across the membrane by diffusion. Because the membrane acts as a barrier for certain molecules and ions, such a concentration gradient across a semipermeable membrane sets up an osmotic flow for the water. Transmembrane protein channels and transporters, Nutrients, such as sugars or amino acids, must enter the cell, such molecules diffuse passively through protein channels such as aquaporins in facilitated diffusion or are pumped across the membrane by transmembrane transporters. Protein channel proteins, also called permeases, are quite specific, recognizing and transporting only a limited food group of chemical substances. Endocytosis, Endocytosis is the process in which cells absorb molecules by engulfing them, the plasma membrane creates a small deformation inward, called an invagination, in which the substance to be transported is captured. The deformation then pinches off from the membrane on the inside of the cell, Endocytosis is a pathway for internalizing solid particles, small molecules and ions, and macromolecules. Endocytosis requires energy and is thus a form of active transport and this is the process of exocytosis
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Cytoplasm
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In cell biology, the cytoplasm is the material within a living cell, excluding the cell nucleus. It comprises cytosol and the organelles – the cells internal sub-structures, all of the contents of the cells of prokaryotic organisms are contained within the cytoplasm. Within the cells of organisms the contents of the cell nucleus are separated from the cytoplasm. The cytoplasm is about 80% water and usually colorless, the submicroscopic ground cell substance or cytoplasmatic matrix which remains after exclusion the cell organelles and particles is groundplasm. It is within the cytoplasm that most cellular activities occur, such as many metabolic pathways including glycolysis, the concentrated inner area is called the endoplasm and the outer layer is called the cell cortex or the ectoplasm. Movement of calcium ions in and out of the cytoplasm is an activity for metabolic processes. In plants, movement of the cytoplasm around vacuoles is known as cytoplasmic streaming, the term was introduced by Rudolf von Kölliker in 1863, originally as a synonym for protoplasm, but later it has come to mean the cell substance and organelles outside the nucleus. There has been disagreement on the definition of cytoplasm, as some authors prefer to exclude from it some organelles. The physical properties of the cytoplasm have been contested in recent years and it remains uncertain how the varied components of the cytoplasm interact to allow movement of particles and organelles while maintaining the cell’s structure. The flow of cytoplasmic components plays an important role in cellular functions which are dependent on the permeability of the cytoplasm. An example of function is cell signalling, a process which is dependent on the manner in which signaling molecules are allowed to diffuse across the cell. While small signaling molecules like calcium ions are able to diffuse with ease, larger molecules, the irregular dynamics of such particles have given rise to various theories on the nature of the cytoplasm. There has long been evidence that the cytoplasm behaves like a sol-gel and it is thought that the component molecules and structures of the cytoplasm behave at times like a disordered colloidal solution and at other times like an integrated network, forming a solid mass. Recently it has proposed that the cytoplasm behaves like a glass-forming liquid approaching the glass transition. A cells ability to vitrify in the absence of activity, as in dormant periods. There has been examining the motion of cytoplasmic particles independent of the nature of the cytoplasm. In such an approach, the aggregate random forces within the cell caused by motor proteins explain the non-Brownian motion of cytoplasmic constituents. The three major elements of the cytoplasm are the cytosol, organelles and inclusions, the cytosol is the portion of the cytoplasm not contained within membrane-bound organelles
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Cell (biology)
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The cell is the basic structural, functional, and biological unit of all known living organisms. A cell is the smallest unit of life that can replicate independently, the study of cells is called cell biology. Cells consist of cytoplasm enclosed within a membrane, which contains many such as proteins. Organisms can be classified as unicellular or multicellular, while the number of cells in plants and animals varies from species to species, humans contain more than 10 trillion cells. Most plant and animal cells are only under a microscope. The cell was discovered by Robert Hooke in 1665, who named the unit for its resemblance to cells inhabited by Christian monks in a monastery. Cells emerged on Earth at least 3.5 billion years ago, Cells are of two types, eukaryotic, which contain a nucleus, and prokaryotic, which do not. Prokaryotes are single-celled organisms, while eukaryotes can be either single-celled or multicellular, prokaryotic cells were the first form of life on Earth, characterised by having vital biological processes including cell signaling and being self-sustaining. They are simpler and smaller than eukaryotic cells, and lack membrane-bound organelles such as the nucleus, prokaryotes include two of the domains of life, bacteria and archaea. The DNA of a prokaryotic cell consists of a chromosome that is in direct contact with the cytoplasm. The nuclear region in the cytoplasm is called the nucleoid, most prokaryotes are the smallest of all organisms ranging from 0.5 to 2.0 µm in diameter. Though most prokaryotes have both a cell membrane and a wall, there are exceptions such as Mycoplasma and Thermoplasma which only possess the cell membrane layer. The envelope gives rigidity to the cell and separates the interior of the cell from its environment, the cell wall consists of peptidoglycan in bacteria, and acts as an additional barrier against exterior forces. It also prevents the cell from expanding and bursting from osmotic pressure due to a hypotonic environment, some eukaryotic cells also have a cell wall. Inside the cell is the region that contains the genome, ribosomes. The genetic material is found in the cytoplasm. Prokaryotes can carry extrachromosomal DNA elements called plasmids, which are usually circular, linear bacterial plasmids have been identified in several species of spirochete bacteria, including members of the genus Borrelia notably Borrelia burgdorferi, which causes Lyme disease. Though not forming a nucleus, the DNA is condensed in a nucleoid, plasmids encode additional genes, such as antibiotic resistance genes
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Cleavage (embryo)
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In embryology, cleavage is the division of cells in the early embryo. The zygotes of many species undergo rapid cell cycles with no significant growth, the different cells derived from cleavage are called blastomeres and form a compact mass called the morula. Cleavage ends with the formation of the blastula, depending mostly on the amount of yolk in the egg, the cleavage can be holoblastic or meroblastic. The pole of the egg with the highest concentration of yolk is referred to as the pole while the opposite is referred to as the animal pole. Cleavage differs from other forms of division in that it increases the number of cells without increasing the mass. This means that each successive subdivision, the ratio of nuclear to cytoplasmic material increases. The rapid cell cycles are facilitated by maintaining levels of proteins that control cell cycle progression such as the cyclins. The processes of karyokinesis and cytokinesis work together to result in cleavage, the mitotic apparatus is made up of a central spindle and polar asters made up of polymers of tubulin protein called microtubules. The asters are nucleated by centrosomes and the centrosomes are organized by centrioles brought into the egg by the sperm as basal bodies, cytokinesis is mediated by the contractile ring made up of polymers of actin protein called microfilaments. Karyokinesis and cytokinesis are independent but spatially and temporally coordinated processes, while mitosis can occur in the absence of cytokinesis, cytokinesis requires the mitotic apparatus. The end of cleavage coincides with the beginning of zygotic transcription and this point is referred to as the midblastula transition and appears to be controlled by the nuclear, cytoplasmic ratio. Determinate cleavage is in most protostomes and it results in the developmental fate of the cells being set early in the embryo development. Each blastomere produced by early embryonic cleavage does not have the capacity to develop into a complete embryo, a cell can only be indeterminate if it has a complete set of undisturbed animal/vegetal cytoarchitectural features. It is characteristic of deuterostomes – when the cell in a deuterostome embryo divides. These holoblastic cleavage planes pass all the way through isolecithal zygotes during the process of cytokinesis, coeloblastula is the next stage of development for eggs that undergo these radial cleavaging. In holoblastic eggs, the first cleavage always occurs along the axis of the egg. From here, the arrangement of blastomeres can follow various patterns, due to different planes of cleavage. Bilateral The first cleavage results in bisection of the zygote into left, the following cleavage planes are centered on this axis and result in the two halves being mirror images of one another
25.
Vitamin
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A vitamin is an organic compound and a vital nutrient that an organism requires in limited amounts. For example, ascorbic acid is a vitamin for humans, supplementation is important for the treatment of certain health problems, but there is little evidence of nutritional benefit when used by otherwise healthy people. Thirteen vitamins are universally recognized at present, Vitamins are classified by their biological and chemical activity, not their structure. Thus, each vitamin refers to a number of compounds that all show the biological activity associated with a particular vitamin. Such a set of chemicals is grouped under an alphabetized vitamin generic descriptor title, such as vitamin A, which includes the compounds retinal, retinol, and four known carotenoids. Vitamers by definition are convertible to the form of the vitamin in the body. Some, such as vitamin D, have hormone-like functions as regulators of mineral metabolism, or regulators of cell and tissue growth and differentiation. The largest number of vitamins, the B complex vitamins, function as cofactors or the precursors for them. In this role, vitamins may be bound to enzymes as part of prosthetic groups, For example. They may also be less tightly bound to enzyme catalysts as coenzymes, for example, folic acid may carry methyl, formyl, and methylene groups in the cell. Although these roles in assisting enzyme-substrate reactions are vitamins best-known function, study of structural activity, function and their role in maintaining health is called vitaminology. Each vitamin is typically used in reactions, and therefore most have multiple functions. Vitamins are essential for the growth and development of a multicellular organism. Using the genetic blueprint inherited from its parents, a fetus begins to develop from the nutrients it absorbs and it requires certain vitamins and minerals to be present at certain times. These nutrients facilitate the chemical reactions that produce among other things, skin, bone, if there is serious deficiency in one or more of these nutrients, a child may develop a deficiency disease. Even minor deficiencies may cause permanent damage, for the most part, vitamins are obtained with food, but a few are obtained by other means. Humans can produce some vitamins from precursors they consume, examples include vitamin A, produced from beta carotene, and niacin, from the amino acid tryptophan. In those who are healthy, there is little evidence that supplements have any benefits with respect to cancer or heart disease
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Fat
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Fat is one of the three main macronutrients, along with carbohydrate and protein. Fats, also known as triglycerides, are esters of three fatty acid chains and the alcohol glycerol, the terms oil, fat, and lipid are often confused. Oil normally refers to a fat with short or unsaturated fatty acid chains that is liquid at room temperature, lipid is the general term, as a lipid is not necessarily a triglyceride. Fats, like lipids, are generally hydrophobic, and are soluble in organic solvents. Fat is an important foodstuff for many forms of life, and they are a necessary part of the diet of most heterotrophs. Some fatty acids that are set free by the digestion of fats are called essential because they cannot be synthesized in the body from simpler constituents, there are two essential fatty acids in human nutrition, alpha-linolenic acid and linoleic acid. Other lipids needed by the body can be synthesized from these, fats and other lipids are broken down in the body by enzymes called lipases produced in the pancreas. Fats and oils are categorized according to the number and bonding of the atoms in the aliphatic chain. Fats that are saturated fats have no double bonds between the carbons in the chain, unsaturated fats have one or more double bonded carbons in the chain. The nomenclature is based on the end of the chain. This end is called the end or the n-end. Thus alpha-linolenic acid is called an omega-3 fatty acid because the 3rd carbon from that end is the first double bonded carbon in the counting from that end. Some oils and fats have double bonds and are therefore called polyunsaturated fats. Unsaturated fats can be divided into cis fats, which are the most common in nature, and trans fats. Unsaturated fats can be altered by reaction with hydrogen effected by a catalyst and this action, called hydrogenation, tends to break all the double bonds and makes a fully saturated fat. However, trans fats are generated during hydrogenation as contaminants created by a side reaction on the catalyst during partial hydrogenation. Saturated fats can stack themselves in a closely packed arrangement, so they can easily and are typically solid at room temperature. For example, animal fats tallow and lard are high in saturated fatty acid content and are solids, olive and linseed oils on the other hand are unsaturated and liquid
27.
Cholesterol
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Cholesterol, from the Ancient Greek chole- and stereos followed by the chemical suffix -ol for an alcohol, is an organic molecule. Cholesterol enables animal cells to dispense with a wall, thereby allowing animal cells to change shape rapidly. In addition to its importance for cell structure, cholesterol also serves as a precursor for the biosynthesis of steroid hormones, bile acid. Cholesterol is the principal sterol synthesized by all animals, in vertebrates, hepatic cells typically produce the greatest amounts. It is absent among prokaryotes, although there are exceptions, such as Mycoplasma. François Poulletier de la Salle first identified cholesterol in solid form in gallstones in 1769, however, it was not until 1815 that chemist Michel Eugène Chevreul named the compound cholesterine. Furthermore, it can be absorbed directly from animal-based foods, a human male weighing 68 kg normally synthesizes about 1 gram per day, and his body contains about 35 g, mostly contained within the cell membranes. Typical daily cholesterol dietary intake for a man in the United States is 307 mg, most ingested cholesterol is esterified, and esterified cholesterol is poorly absorbed. The body also compensates for any absorption of cholesterol by reducing cholesterol synthesis. For these reasons, cholesterol in food, seven to ten hours after ingestion, has little and it is also important to recognize, however, that the concentrations measured in the samples of blood plasma vary with the measurement methods used. Cholesterol is recycled in the body, the liver excretes it in a non-esterified form into the digestive tract. Typically, about 50% of the excreted cholesterol is reabsorbed by the small intestine back into the bloodstream, plants make cholesterol in very small amounts. Plants manufacture phytosterols, which can compete with cholesterol for reabsorption in the intestinal tract, when intestinal lining cells absorb phytosterols, in place of cholesterol, they usually excrete the phytosterol molecules back into the GI tract, an important protective mechanism. Cholesterol, given that it composes about 30% of all cell membranes, is required to build. The membrane remains stable and durable without being rigid, allowing cells to change shape. In this structural role, cholesterol also reduces the permeability of the membrane to neutral solutes, hydrogen ions. Within the cell membrane, cholesterol also functions in intracellular transport, cell signaling, cholesterol is essential for the structure and function of invaginated caveolae and clathrin-coated pits, including caveola-dependent and clathrin-dependent endocytosis. The role of cholesterol in endocytosis of these types can be investigated by using methyl beta cyclodextrin to remove cholesterol from the plasma membrane, in multiple layers, cholesterol and phospholipids, both electrical insulators, can facilitate speed of transmission of electrical impulses along nerve tissue
28.
Protein
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Proteins are large biomolecules, or macromolecules, consisting of one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, a linear chain of amino acid residues is called a polypeptide. A protein contains at least one long polypeptide, short polypeptides, containing less than 20–30 residues, are rarely considered to be proteins and are commonly called peptides, or sometimes oligopeptides. The individual amino acid residues are bonded together by peptide bonds, the sequence of amino acid residues in a protein is defined by the sequence of a gene, which is encoded in the genetic code. In general, the code specifies 20 standard amino acids, however. Sometimes proteins have non-peptide groups attached, which can be called prosthetic groups or cofactors, proteins can also work together to achieve a particular function, and they often associate to form stable protein complexes. Once formed, proteins only exist for a period of time and are then degraded and recycled by the cells machinery through the process of protein turnover. A proteins lifespan is measured in terms of its half-life and covers a wide range and they can exist for minutes or years with an average lifespan of 1–2 days in mammalian cells. Abnormal and or misfolded proteins are degraded more rapidly due to being targeted for destruction or due to being unstable. Like other biological macromolecules such as polysaccharides and nucleic acids, proteins are essential parts of organisms, many proteins are enzymes that catalyse biochemical reactions and are vital to metabolism. Proteins also have structural or mechanical functions, such as actin and myosin in muscle and the proteins in the cytoskeleton, other proteins are important in cell signaling, immune responses, cell adhesion, and the cell cycle. In animals, proteins are needed in the diet to provide the essential amino acids that cannot be synthesized, digestion breaks the proteins down for use in the metabolism. Methods commonly used to study structure and function include immunohistochemistry, site-directed mutagenesis, X-ray crystallography, nuclear magnetic resonance. Most proteins consist of linear polymers built from series of up to 20 different L-α-amino acids, all proteinogenic amino acids possess common structural features, including an α-carbon to which an amino group, a carboxyl group, and a variable side chain are bonded. Only proline differs from this structure as it contains an unusual ring to the N-end amine group. The amino acids in a chain are linked by peptide bonds. Once linked in the chain, an individual amino acid is called a residue, and the linked series of carbon, nitrogen. The peptide bond has two forms that contribute some double-bond character and inhibit rotation around its axis, so that the alpha carbons are roughly coplanar
29.
Fried egg
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A fried egg is a cooked dish commonly made using a fresh hens egg, fried whole with minimal accompaniment. Fried eggs are eaten for breakfast in English-speaking countries but may also be served at other times of the day. Fried eggs over pan-fried potatoes is another dish, sometimes served with spinach as a third component of the meal. Some German cooks break the yolk and distribute it across the surface of the white during the frying, all of the above are typically lunch, rather than breakfast, dishes, although fried eggs themselves are a common part of a German breakfast. Fried egg prepared sunny side up is known as volské oko or buličí oko in Czech cuisine and they are served either alone as part of breakfast, or for lunch with side of spinach and boiled potatoes. Americans use many different terms to describe fried eggs, including and this term is also occasionally used in Canada. Over medium Cooked on both sides, the yolk is cooked through but soft and near liquid at the center, the egg white is thoroughly cooked. Over hard Cooked on both sides with the broken, until set or hard. Over well Cooked on both sides with the yolk fully cooked through and hard, sunny side up Cooked on one side only, until the egg white is set, but the yolk remains liquid. This is often simply as eggs up. Gently splashing the hot cooking oil or fat over the sunny side uncooked white may be done to thoroughly cook the white. Covering the frying pan with a lid during cooking allows for a less runny egg, in Egypt, fried eggs are a common breakfast food. They are prepared plain, with oil or native butter or ghee only. These typically include tomatoes, various types of cheeses, beef sausage, bastirma, or specially prepared minced meat with onions and spices, less frequently encountered are star eggs, a dish somewhat similar to a Scotch egg prepared by deep frying a breaded boiled egg in vegetable oil. Some restaurants also refer to them as egg fry or egg half fry, bullseyes are a common street vendor dish in South India. They are commonly served alone or as an accompaniment to a variety of dishes including dosa, paratha, or roti, with a variety of such as mustard oil. During or after the stage, they are sometimes sprinkled lightly with condiments such as black pepper, chili powder, green chilis. In central and northern Indias English-speaking middle classes and mid-level restaurants, single-fried refers to side up
30.
Omelette
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In cuisine, an omelette or omelet is a dish made from beaten eggs quickly fried with butter or oil in a frying pan. It is quite common for the omelette to be folded around a filling such as cheese, chives, vegetables, meat, whole eggs or sometimes only egg whites are beaten with a small amount of milk or cream, or even water. The fluffy omelette is a version of an ancient food. According to Alan Davidson, the French word omelette came into use during the mid-16th century, rabelais mentions an homelaicte doeufs, Olivier de Serres an amelette, François Pierre La Varennes Le cuisinier françois has aumelette, and the modern omelette appears in Cuisine bourgoise. Napoleon feasted on a prepared by a local innkeeper. He then ordered the townspeople to gather all the eggs in the village, in turn, that record was surpassed on August 11,2012, by an omelette cooked by the Ferreira do Zêzere City Council in Santarém, Portugal. This record-breaking omelette weighed 6,466 kg, and required 145,000 eggs, nargesi or Spinach Omelette, an Iranian dish, is made with fried onions and spinach, and is spiced with salt, garlic, and pepper. Khagineh, an Iranian omelette, is made of egg beaten with sugar, in Iran, beaten eggs are quickly cooked with butter or oil in a frying pan. Baghala ghatogh, an Iranian dish made with Baghalas, dill, eggs, a Chinese omelette can be egg foo yung or an oyster omelette. A Denver omelette, also known as a Southwest omelette or Western omelette, is a filled with diced ham, onions. Often served in the Southwestern United States, this omelette sometimes has a topping of cheese, a Hangtown fry, containing bacon and breaded oysters, is an unusual omelette that originated in Placerville, California, during the gold rush. An egg white omelette is a variation which omits the yolks to remove fat and cholesterol, the French omelette is smoothly and briskly cooked in an extremely hot pan specially made for the purpose. The technique relies on clarified butter in relatively great ratio to the eggs, good with just salt and pepper, this omelette is often flavored with tomato and finely chopped herbs or chopped onions. They can be rolled out in a design or just simply slid out of the pan directly into a plate and. In France, omelettes are often made With cheese, a Greek omeleta consists of pan-fried or sautéed vegetables, pastas, or leftovers over which beaten eggs are poured to act as a binder. It is then cooked with a plate over the top, flipped onto the plate, unlike many of the other omelette styles, the Greek omeleta is more often used to showcase leftovers or fresh ingredients rather than to emphasise the eggs. A frittata is a kind of open-faced Italian omelette that can contain cheese, vegetables, except for the cooking oil, all ingredients are fully mixed with the eggs before cooking starts. An Indian omelette, often called a Masala omelette, is made with the addition of spices
31.
Scrambled eggs
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Scrambled eggs is a dish made from whites and yolks of eggs stirred or beaten together in a pan while being gently heated, typically with salt and butter and variable other ingredients. The mixture can be poured into a hot pan containing melted butter or oil, the heat is turned down and the eggs are stirred as they cook. This creates small, soft curds of egg, unlike pancake or omelette scrambled egg is virtually never browned. A thin pan is preferable to prevent browning, with continuous stirring, and not allowing the eggs to stick to the pan, the eggs themselves will maintain the pan temperature at about the boiling point of water, until they coagulate. A thick pan will not allow the eggs to regulate the pan temperature, once the liquid has mostly set, additional ingredients such as ham, herbs, cheese or cream may be folded in over low heat, just until incorporated. The eggs are usually slightly undercooked when removed from heat, since the eggs continue to set. If any liquid is seeping from the eggs, this is a sign of undercooking, overcooking or adding undercooked high-moisture vegetables. In the classic French cooking method, Escoffier describes using a double boiler as the heating source, the eggs are directly placed in the cooker and mixed during the heating and not before. Cooking by this method prevents the eggs from browning while being cooked, Scrambled eggs à larlésienne - with zucchini pulp and a concentrated garlic-flavored tomato fondue served in hollowed-out courgettes and sprinkled with Parmesan cheese. Scrambled eggs à laméricaine - with pan-fried smoked bacon, garnished with slices of broiled bacon, egg bhurji - Indian variant of scrambled eggs. Additions include onions, green chili, chopped ginger, turmeric powder, sprinkled with chopped green coriander and eaten with roti. Another variant of egg bhurji is the Parsi akuri, scotch woodcock - British variant of scrambled eggs, served over toast that has been spread with Gentlemans Relish. Soy scrambled eggs - mixed with soy sauce and often eaten with congee, onions and scrambled eggs - another variant of scrambled eggs eaten in the Philippines. The onions are fried first then the egg mixture is poured over them to cook, or the onions are mixed with the egg mixture. Scrambled eggs with sucuk or pastırma, sucuklu yumurta and pastırmalı yumurta respectively - Scrambled eggs are mixed with Turkish beef sausages and it is cooked in a sahan with butter or olive oil. In Turkey and Egypt it is regularly for breakfast. Scrambled eggs with digüeñes - a variation from Chilean cuisine in which the eggs are fried together with the native fungus Cyttaria espinosae, migas - a Tex-Mex dish consisting of scrambled eggs augmented with strips of corn tortilla, to which vegetables and meat may be added. Stir-fried tomato and scrambled eggs - a very common main course in China and it is quickly and easily prepared, and so is a favourite among teens and university students
32.
Separating eggs
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Separating eggs is a process, generally used in cooking, in which the egg yolk is removed from the egg white. This allows one part of the egg to be used without the other part, recipes for custard call for egg yolks, for example. The most common reason for separating eggs is so the whites can be whipped, all methods for separating eggs make use of the fact that the yolk can hold itself together while the white is more runny. Since the yolks of eggs are more watery, which makes separation difficult. Although many recipes require eggs to be at room temperature, it is easiest to separate eggs that are cold, eggs that are at room temperature can be separated, but this requires greater caution to avoid breaking the yolk. One solution is to separate the eggs, cover them, in this method eggs should not be allowed to sit too long because of the risk of bacteria growth. An alternate solution is to bring the bowl of egg whites up to temperature by placing it in another bowl of hot water, different methods, Break the egg and use your fingers to strain out the yolk, while the whites run into the bowl below. Crack the egg in half and cradle the yolk in one half of the shell while draining the white into a bowl. If some white is left with the yolk, carefully pass the yolk back, then deposit the yolk into another bowl. This method is discouraged by food safety experts due to the possibility of salmonella contamination, use an egg separator, a device that can be set over a bowl, with a cup to catch the yolk and vents to allow the white to pass down. Break the egg into a funnel, capturing the yolk, Break the egg on to a plate, and trap the yolk under a glass. Carefully, drain off the whites, lifting the glass slightly, use a needle to pierce the egg and run the whites out, leaving the yolk inside
33.
Mayonnaise
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Mayonnaise is a thick, creamy dressing often used as a condiment. It is an emulsion of oil, egg yolk, and either vinegar or lemon juice, with many options for embellishment with other herbs. Proteins and lecithin in the egg yolk serve as emulsifiers in both mayonnaise and hollandaise sauce, commercial egg-free alternatives are available for vegans and others who want to avoid animal products and cholesterol, or who are allergic to eggs. Mayonnaise varies in color, but is white, cream. It may range in texture from that of light cream to a thick gel, the word mayonnaise was not used for a dressing before the start of the 19th century. The earliest reference appears to be by Alexandre Viard, who never quite gives a recipe for the dressing itself. At that point, the sauce was made with aspic or jelly, in 1815, Louis Eustache Ude wrote, No 58. —Mayonnaise. Take three spoonfuls of Allemande, six ditto of aspic, and two of oil, add a little tarragon vinegar, that has not boiled, some pepper and salt, and minced ravigotte, or merely some parsley. Then put in the members of fowl, or fillets of soles and your mayonnaise must be put to ice, neither are you to put the members into your sauce till it begins to freeze. Next dish your meat or fish, mask with the sauce before it be quite frozen, and garnish your dish with whatever you think proper, as beet root, jelly, nasturtiums, &c. In a 1820 work, Viard describes something like the more familiar emulsified version, This sauce is made to take in many ways, with raw egg yolks, with gelatine and this sauce is used for cold fish entrees, or salad of vegetables cooked in salt water. According to this version, the sauce was known as salsa mayonesa in Spanish and maonesa in Catalan. The Larousse Gastronomique suggests, Mayonnaise, in our view, is a corruption of moyeunaise, derived from the very old French word moyeu. It is highly probable that wherever olive oil existed, a preparation of oil and egg came about — particularly in the Mediterranean region. According to the Oxford English Dictionary, the term mayonnaise was in use in English as early as 1823 in the journal of Lady Blessington, traditional mayonnaise is a mixture of egg, vinegar, oil and spices. Mayonnaise made in this fashion typically contains 70–80% fat, despite the high oil content relative to water, mayonnaise is an oil-in-water emulsion. This emulsion is formed by first mixing the eggs, vinegar and mustard and this results in an emulsion consisting of a closely packed foam of oil droplets. By contrast, if the oil and aqueous phases are mixed all at once the result is a water-in-oil emulsion similar in viscosity to the oil from which it is made, oil may account for 75% or more of the total volume
34.
Custard
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Custard is a variety of culinary preparations based on a cooked mixture of milk or cream and egg yolk. Depending on how much egg or thickener is used, custard may vary in consistency from a thin pouring sauce to a thick pastry cream used to fill éclairs, most common custards are used as desserts or dessert sauces and typically include sugar and vanilla. Custard bases may also be used for quiches and other savory foods, sometimes flour, corn starch, or gelatin is added as in pastry cream or crème pâtissière. Custard preparation is an operation, because a temperature increase of 3–6 °C leads to overcooking and curdling. Generally, a fully cooked custard should not exceed 80 °C, a water bath slows heat transfer and makes it easier to remove the custard from the oven before it curdles. Mixtures of milk and eggs thickened by heat have long been part of European cuisine, examples include Crustardes of flessh and Crustade, in the 14th century English collection The Forme of Cury. These recipes include solid ingredients such as meat, fish, stirred custards cooked in pots are also found under the names Creme Boylede and Creme boiled. In modern times, the custard is sometimes applied to starch-thickened preparations like blancmange. While custard may refer to a variety of thickened dishes. Crème pâtissière is a key ingredient in many French desserts including mille-feuille and it is also used in Italian pastry and sometimes in Boston cream pie. Although egg thickens the custard, the effect is minimal, with the majority of thickening resulting from starch, corn flour or flour thicken at 100 °C and as such many recipes instruct the pastry cream to be boiled. Once cooled, the amount of starch in pastry cream sets the cream, when gelatin is added, it is known as crème anglaise collée. When starch is used alone as a thickener, the result is a blancmange, in the United Kingdom, custard has various traditional recipes some thickened principally with cornflour rather than the egg component, others involving regular flour, see custard powder. After the custard has thickened, it may be mixed with other ingredients, mixed with beaten egg whites and gelatin, it is chiboust cream, mixed with whipped cream. Beating in softened butter produces German buttercream or crème mousseline, a quiche is a savoury custard tart. Some kinds of timbale or vegetable loaf are made of a custard base mixed with chopped savoury ingredients, Custard royale is a thick custard cut into decorative shapes and used to garnish soup, stew or broth. In German it is known as Eierstich and is used as a garnish in German Wedding Soup, chawanmushi is a Japanese savoury custard, steamed and served in a small bowl or on a saucer. Chinese steamed egg is a similar but larger savoury egg dish, Custard may also be used as a top layer in gratins, such as the South African bobotie and many Balkan versions of moussaka
35.
Hollandaise sauce
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Hollandaise sauce, also referred to as Dutch sauce, is an emulsion of egg yolk, liquid butter, water and lemon juice, whisked together over the low heat of a double boiler. Additional salt, white pepper and/or cayenne pepper is used for seasoning, Hollandaise is one of the five sauces in the French haute cuisine mother sauce repertoire. These types of sauces are considered mayonnaise sauces as they are, like mayonnaise and it is so named because it was believed to have mimicked a Dutch sauce for the King of the Netherlands state visit to France. Hollandaise sauce is known as a key ingredient of Eggs Benedict. Sauce Hollandaise translates from French as Dutch sauce, the recipe for Dutch sauce would appear to be a classic Hollandaise however, there seems to be little explanation as to why it was renamed. Huguenots, returning from Holland, are said to have brought the recipe back to France that they had developed abroad, the first documented mention of a recipe is from 1651 in François Pierre La Varennes Le Cuisinier François for asparagus with fragrant sauce. Francois is attributed with bringing out of the Middle ages with his publication. The French developed Isigny sauce, named after the Norman town of Isigny-sur-Mer which produces the finest French butter and is very similer. While the Norman butter helped the sauce reach a status, it actually dates back to when the Dutch sold butter. By the 19th century, sauces had been classified into four distinct selections by Chef Marie-Antoine Carême, one of Carêmes family of sauces was allemande which was a stock based sauce using egg and lemon juice. Auguste Escoffier updated that list in the early 20th century by replacing allemande with Hollandaise sauce as part of his family of five mother sauces of Haute cuisine, egg emulsion sauces include mayonnaise, Hollandaise and Béarnaise. For hollandaise sauce, egg yolks and water, lemon juice or vinegar are emulsified, unlike custard, the egg does not coagulate. An emulsion is a mixture of two or more liquids that are normally immiscible, droplets of the butter become suspended in the water and lemon juice once emulsion occurs. While emulsions can be stable or unstable, hollandaise is made stable by the addition of eggs which contain lecithin, combining with the oil and water. To make hollandaise sauce, the yolks are separated and added to a butter base with small amounts of water, vinegar or lemon juice with pepper. A stainless steel bowl over a pan with a small amount of water may also be used. The water should not touch the bowl or boil, just simmer, the key to the recipe is to heat the ingredients without curdling the egg. Add the egg and liquid ingredients first and whisk together with a wire whisk until frothy, add the egg and liquid froth to the to the double boiler of the simmering water and whisk quickly and continuously
36.
Avgolemono
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Avgolemono or egg-lemon sauce, is a family of Mediterranean sauces and soups made with egg yolk and lemon juice mixed with broth, heated until they thicken. In Sephardic Jewish cuisine – which possibly invented it –, it is called agristada or salsa blanco, in Arabic, it is called tarbiya or beida bi-lemoune egg with lemon, and in Turkish terbiye. It is also used in Balkan cuisine. In some Middle Eastern cuisines, it is used as a sauce for chicken or fish, among Italian Jews, it is served as a sauce for pasta or meat. As a soup, it starts with chicken broth, though meat, fish. Typically, rice, orzo, pastina, or tapioca are cooked in the broth before the mixture of eggs and its consistency varies from near-stew to near-broth. It is often served with pieces of the meat and vegetables reserved from the broth, magiritsa soup is a Greek avgolemono soup of lamb offal served to break the fast of Great Lent. The soup is made with whole eggs, sometimes with just yolks. The whites may be beaten into a foam separately before mixing with the yolks and lemon juice, the starch of the pasta or rice contributes to stabilizing the emulsion. Egg-lemon sauce may originally be a Jewish dish, agristada was made by Jews in Iberia before the expulsion from Spain with verjuice, pomegranate juice, or bitter orange juice, but not vinegar. In later periods, lemon became the standard souring agent, List of egg dishes List of lemon dishes and beverages List of sauces List of soups Alan Davidson, The Oxford Companion to Food, Oxford,1999
37.
Tempera
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Tempera, also known as egg tempera, is a permanent, fast-drying painting medium consisting of colored pigments mixed with a water-soluble binder medium. Tempera also refers to the paintings done in this medium, Tempera paintings are very long lasting, and examples from the 1st centuries AD still exist. Egg tempera was a method of painting until after 1500 when it was superseded by the invention of oil painting. Tempera painting has been found on early Egyptian sarcophagi decorations, many of the Fayum mummy portraits use tempera, sometimes in combination with encaustic. A related technique has been used also in ancient and early medieval paintings found in several caves, high-quality art with the help of tempera was created in Bagh Caves between the late 4th and 10th centuries AD and in the 7th century AD in Ravan Chhaya rock shelter, Orissa. Tempera painting was the panel painting medium for nearly every painter in the European Medieval. For example, every surviving panel painting by Michelangelo is egg tempera, oil paint, which may have originated in Afghanistan between the 5th and 9th centuries and migrated westward in the Middle Ages eventually superseded tempera. Oil replaced tempera as the medium used for creating artwork during the 15th century in Early Netherlandish painting in northern Europe. Around 1500, oil paint replaced tempera in Italy, in the 19th and 20th centuries, there were intermittent revivals of tempera technique in Western art, among the Pre-Raphaelites, Social Realists, and others. Tempera painting continues to be used in Greece and Russia where it is the medium for Orthodox icons. Tempera is traditionally created by hand-grinding dry powdered pigments into an agent or medium, such as egg, glue, honey, water, milk. Tempera painting starts with placing an amount of the powdered pigment onto a palette, dish or bowl and adding about an equal volume of the binder. Some pigments require slightly more binder, some require less, a few drops of distilled water are added, then the binder is added in small increments to the desired transparency. The more egg emulsion, the more transparent the paint, the most common form of classical tempera painting is egg tempera. For this form most often only the contents of the egg yolk is used, the white of the egg and the membrane of the yolk are discarded. Egg yolk is never used by itself with pigment, it dries almost immediately, some agent is always added, in variable proportions. One recipe calls for vinegar, other recipes suggest white wine, some schools of egg tempera use various mixtures of egg yolk and water. The paint mixture has to be adjusted to maintain a balance between a greasy and watery consistency by adjusting the amount of water and yolk
38.
Agar plate
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An agar plate is a Petri dish that contains a growth medium used to culture microorganisms or small plants like the moss Physcomitrella patens. Selective growth compounds may also be added to the media, such as antibiotics, individual microorganisms placed on the plate will grow into individual colonies, each a clone genetically identical to the individual ancestor organism. Some commonly used agar plate types are, Blood agar plates contain mammalian blood, bAPs are enriched, differential media used to isolate fastidious organisms and detect hemolytic activity. β-Hemolytic activity will show lysis and complete digestion of red blood cell contents surrounding a colony, α-Hemolysis will only cause partial lysis of the red blood cells and will appear green or brown, due to the conversion of hemoglobin to methemoglobin. An example of this would be Streptococcus viridans, γ-Hemolysis is the term referring to a lack of hemolytic activity. BAPs also contain meat extract, tryptone, sodium chloride, chocolate agar is a type of blood agar plate in which the blood cells have been lysed by heating the cells to 56 °C. It is used for growing fastidious respiratory bacteria, such as Haemophilus influenzae, no chocolate is actually contained in the plate, it is named for the coloration only. Horse blood agar is a type of blood-enriched microbiological culture media, as it is enriched, it allows the growth of certain fastidious bacteria, and allows indication of haemolytic activity in these bacterial cultures. Thayer-Martin agar is a chocolate agar designed to isolate Neisseria gonorrhoeae, thiosulfate-citrate-bile salts-sucrose agar enhances growth of Vibrio spp. including Vibrio cholerae. Granada medium is used to isolate and differentiate group B Streptococcus, Streptococcus agalactiae from clinical samples and it grows in Granada medium as red colonies and most of accompanying bacteria are inhibited. Hektoen enteric agar is designed to isolate and recover fecal bacteria belonging to the Enterobacteriaceae family and it is particularly useful in isolating Salmonella and Shigella. Lysogeny broth MacConkey agar is a selective and differential medium used to differentiate between Gram-negative bacteria while inhibiting the growth of Gram-positive bacteria, the addition of bile salts and crystal violet to the agar inhibits the growth of most Gram-positive bacteria, making MacConkey agar selective. Lactose and neutral red are added to differentiate the lactose fermenters, an alternative medium, eosin methylene blue serves a similar purpose. Mannitol salt agar is also a selective and differential medium, the mannitol indicates organisms that ferment mannitol, mannitol fermentation produces lactic acid, lowering the pH and turning the plate yellow. The salt is to select for halophiles, organisms that cannot withstand a high salt content are unable to grow well, mueller-Hinton agar contains beef infusion, peptone, and starch, and is used primarily for antibiotic susceptibility testing. It can be in a form of blood agar, nutrient agar is usually used for growth of nonfastidious organisms and observation of pigment production. It is safe to use in science laboratories because it does not selectively grow pathogenic bacteria. Önöz agar allows more rapid bacteriological diagnosis, as Salmonella and Shigella colonies can be clearly and reliably differentiated from other Enterobacteriaceae, the yields of Salmonella from stool samples obtained, when using this medium, are higher than those obtained with LEIFSON agar or Salmonella–Shigella agar
39.
Clostridium perfringens
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Clostridium perfringens is a Gram-positive, rod-shaped, anaerobic, spore-forming pathogenic bacterium of the genus Clostridium. C. perfringens is everpresent in nature and can be found as a component of decaying vegetation, marine sediment, the intestinal tract of humans and other vertebrates, insects. It has the shortest reported generation time of any organism at 6.3 minutes in thioglycollate medium, C. perfringens is the third most common cause of food poisoning in the United Kingdom and the United States though it can sometimes be ingested and cause no harm. Infections due to C. perfringens show evidence of necrosis, bacteremia, emphysematous cholecystitis, and gas gangrene. The toxin involved in gas gangrene is known as α-toxin, which inserts into the membrane of cells. C. perfringens can participate in polymicrobial anaerobic infections, Clostridium perfringens is commonly encountered in infections as a component of the normal flora. In this case, its role in disease is minor, the action of C. perfringens on dead bodies is known to mortuary workers as tissue gas and can be halted only by embalming. Although they lack flagella, C. perfringens bacteria are able to glide across surfaces because their bodies are lined with filaments from end-to-end, the hypermotile variants such as SM101, are often found arising on the edges of colonies on agar plates. Video microscopy of their gliding movement suggest that they form long, genome sequencing was used to identify the cause of the hypermotile phenotype and their direct derivatives. In comparing them, strains SM124 and SM127, hypermotile derivatives of strains SM101 and SM102, respectively, mutations in cell division genes is the common feature of the hypermotile strains. In the United Kingdom and United States, C, the clostridium perfringens enterotoxin mediating the disease is heat-labile. It can be detected in contaminated food, and feces, incubation time is between six and 24 hours after ingestion of contaminated food. Since C. perfringens forms spores that can withstand cooking temperatures, if cooked food is let stand for long enough, germination can ensue, symptoms typically include abdominal cramping, diarrhea, vomiting, and fever. The whole course usually resolves within 24 hours, but can last up to two weeks in older or infirm hosts, perfringens poisoning can also lead to another disease known as enteritis necroticans, this is caused by the same strain that causes perfringens food poisoning. However this infection is often fatal, large numbers of C. perfringens grow in the intestines, and secrete exotoxin. This exotoxin causes necrosis of the intestines, varying levels of hemorrhaging, inflammation usually occurs in sections of the jejunum, midsection of the small intestine. This disease eventually leads to septic shock and death and this particular disease is rare in the United States, typically it occurs in populations with a higher risk. This disease is contracted in populations living in New Guinea, parts of Africa, Central America, South America, many cases of C. perfringens food poisoning likely remain subclinical, as antibodies to the toxin are common among the population
