1.
Glycogenin
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Glycogenin is an enzyme involved in converting glucose to glycogen. It acts as a primer, by polymerizing the first few glucose molecules and it is a homodimer of 37-kDa subunits and is classified as a glycosyltransferase. This enzyme belongs to the family of glycosyltransferases, specifically the hexosyltransferases, the systematic name of this enzyme class is UDP-alpha-D-glucose, glycogenin alpha-D-glucosyltransferase. Other names in use include, glycogenin, priming glucosyltransferase. Glycogenin was discovered in 1984 by Dr. William J. Whelan, the main enzyme involved in glycogen polymerisation, glycogen synthase, can only add to an existing chain of at least 4 glucose residues. Glycogenin acts as the primer, to which further glucose monomers may be added and it achieves this by catalyzing the addition of glucose to itself by first binding glucose from UDP-glucose to the hydroxyl group of Tyr-194. Seven more glucoses can be added, each derived from UDP-glucose, once sufficient residues have been added, glycogen synthase takes over extending the chain. Glycogenin remains covalently attached to the end of the glycogen molecule. Patients have been found with defective GYG1, resulting in cells with the inability to store glycogen. Glycogenin at the US National Library of Medicine Medical Subject Headings http, //molbio. med. miami. edu/NewWebsite/Whelan. htm
2.
Atom
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An atom is the smallest constituent unit of ordinary matter that has the properties of a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms, Atoms are very small, typical sizes are around 100 picometers. Atoms are small enough that attempting to predict their behavior using classical physics - as if they were billiard balls, through the development of physics, atomic models have incorporated quantum principles to better explain and predict the behavior. Every atom is composed of a nucleus and one or more bound to the nucleus. The nucleus is made of one or more protons and typically a number of neutrons. Protons and neutrons are called nucleons, more than 99. 94% of an atoms mass is in the nucleus. The protons have an electric charge, the electrons have a negative electric charge. If the number of protons and electrons are equal, that atom is electrically neutral, if an atom has more or fewer electrons than protons, then it has an overall negative or positive charge, respectively, and it is called an ion. The electrons of an atom are attracted to the protons in a nucleus by this electromagnetic force. The number of protons in the nucleus defines to what chemical element the atom belongs, for example, the number of neutrons defines the isotope of the element. The number of influences the magnetic properties of an atom. Atoms can attach to one or more other atoms by chemical bonds to form compounds such as molecules. The ability of atoms to associate and dissociate is responsible for most of the changes observed in nature. The idea that matter is made up of units is a very old idea, appearing in many ancient cultures such as Greece. The word atom was coined by ancient Greek philosophers, however, these ideas were founded in philosophical and theological reasoning rather than evidence and experimentation. As a result, their views on what look like. They also could not convince everybody, so atomism was but one of a number of competing theories on the nature of matter. It was not until the 19th century that the idea was embraced and refined by scientists, in the early 1800s, John Dalton used the concept of atoms to explain why elements always react in ratios of small whole numbers
3.
Molecule
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A molecule is an electrically neutral group of two or more atoms held together by chemical bonds. Molecules are distinguished from ions by their lack of electrical charge, however, in quantum physics, organic chemistry, and biochemistry, the term molecule is often used less strictly, also being applied to polyatomic ions. In the kinetic theory of gases, the molecule is often used for any gaseous particle regardless of its composition. According to this definition, noble gas atoms are considered molecules as they are in fact monoatomic molecules. A molecule may be homonuclear, that is, it consists of atoms of one element, as with oxygen, or it may be heteronuclear. Atoms and complexes connected by non-covalent interactions, such as hydrogen bonds or ionic bonds, are not considered single molecules. Molecules as components of matter are common in organic substances and they also make up most of the oceans and atmosphere. Also, no typical molecule can be defined for ionic crystals and covalent crystals, the theme of repeated unit-cellular-structure also holds for most condensed phases with metallic bonding, which means that solid metals are also not made of molecules. In glasses, atoms may also be together by chemical bonds with no presence of any definable molecule. The science of molecules is called molecular chemistry or molecular physics, in practice, however, this distinction is vague. In molecular sciences, a molecule consists of a system composed of two or more atoms. Polyatomic ions may sometimes be thought of as electrically charged molecules. The term unstable molecule is used for very reactive species, i. e, according to Merriam-Webster and the Online Etymology Dictionary, the word molecule derives from the Latin moles or small unit of mass. Molecule – extremely minute particle, from French molécule, from New Latin molecula, diminutive of Latin moles mass, a vague meaning at first, the vogue for the word can be traced to the philosophy of Descartes. The definition of the molecule has evolved as knowledge of the structure of molecules has increased, earlier definitions were less precise, defining molecules as the smallest particles of pure chemical substances that still retain their composition and chemical properties. Molecules are held together by covalent bonding or ionic bonding. Several types of non-metal elements exist only as molecules in the environment, for example, hydrogen only exists as hydrogen molecule. A molecule of a compound is made out of two or more elements, a covalent bond is a chemical bond that involves the sharing of electron pairs between atoms
4.
Polysaccharide
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They range in structure from linear to highly branched. Examples include storage polysaccharides such as starch and glycogen, and structural polysaccharides such as cellulose, polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure, these macromolecules can have distinct properties from their building blocks. They may be amorphous or even insoluble in water, natural saccharides are generally of simple carbohydrates called monosaccharides with general formula n where n is three or more. Examples of monosaccharides are glucose, fructose, and glyceraldehyde, polysaccharides, meanwhile, have a general formula of Cxy where x is usually a large number between 200 and 2500. When the repeating units in the backbone are six-carbon monosaccharides, as is often the case, the general formula simplifies to n. Polysaccharides are an important class of biological polymers and their function in living organisms is usually either structure- or storage-related. Starch is used as a polysaccharide in plants, being found in the form of both amylose and the branched amylopectin. In animals, the structurally similar glucose polymer is the more densely branched glycogen, glycogens properties allow it to be metabolized more quickly, which suits the active lives of moving animals. Cellulose and chitin are examples of structural polysaccharides, cellulose is used in the cell walls of plants and other organisms, and is said to be the most abundant organic molecule on Earth. It has many such as a significant role in the paper and textile industries, and is used as a feedstock for the production of rayon, cellulose acetate, celluloid. Chitin has a structure, but has nitrogen-containing side branches. It is found in arthropod exoskeletons and in the walls of some fungi. It also has multiple uses, including surgical threads, polysaccharides also include callose or laminarin, chrysolaminarin, xylan, arabinoxylan, mannan, fucoidan and galactomannan. Nutrition polysaccharides are common sources of energy, many organisms can easily break down starches into glucose, however, most organisms cannot metabolize cellulose or other polysaccharides like chitin and arabinoxylans. These carbohydrate types can be metabolized by bacteria and protists. Ruminants and termites, for example, use microorganisms to process cellulose, even though these complex carbohydrates are not very digestible, they provide important dietary elements for humans. Called dietary fiber, these carbohydrates enhance digestion among other benefits, the main action of dietary fiber is to change the nature of the contents of the gastrointestinal tract, and to change how other nutrients and chemicals are absorbed
5.
Animal
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Animals are multicellular, eukaryotic organisms of the kingdom Animalia. The animal kingdom emerged as a clade within Apoikozoa as the group to the choanoflagellates. Animals are motile, meaning they can move spontaneously and independently at some point in their lives and their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later in their lives. All animals are heterotrophs, they must ingest other organisms or their products for sustenance, most known animal phyla appeared in the fossil record as marine species during the Cambrian explosion, about 542 million years ago. Animals can be divided broadly into vertebrates and invertebrates, vertebrates have a backbone or spine, and amount to less than five percent of all described animal species. They include fish, amphibians, reptiles, birds and mammals, the remaining animals are the invertebrates, which lack a backbone. These include molluscs, arthropods, annelids, nematodes, flatworms, cnidarians, ctenophores, the study of animals is called zoology. The word animal comes from the Latin animalis, meaning having breath, the biological definition of the word refers to all members of the kingdom Animalia, encompassing creatures as diverse as sponges, jellyfish, insects, and humans. Aristotle divided the world between animals and plants, and this was followed by Carl Linnaeus, in the first hierarchical classification. In Linnaeuss original scheme, the animals were one of three kingdoms, divided into the classes of Vermes, Insecta, Pisces, Amphibia, Aves, and Mammalia. Since then the last four have all been subsumed into a single phylum, in 1874, Ernst Haeckel divided the animal kingdom into two subkingdoms, Metazoa and Protozoa. The protozoa were later moved to the kingdom Protista, leaving only the metazoa, thus Metazoa is now considered a synonym of Animalia. Animals have several characteristics that set apart from other living things. Animals are eukaryotic and multicellular, which separates them from bacteria and they are heterotrophic, generally digesting food in an internal chamber, which separates them from plants and algae. They are also distinguished from plants, algae, and fungi by lacking cell walls. All animals are motile, if only at life stages. In most animals, embryos pass through a stage, which is a characteristic exclusive to animals. With a few exceptions, most notably the sponges and Placozoa and these include muscles, which are able to contract and control locomotion, and nerve tissues, which send and process signals
6.
Fungus
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A fungus is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from the other eukaryotic life kingdoms of plants, a characteristic that places fungi in a different kingdom from plants, bacteria and some protists, is chitin in their cell walls. Similar to animals, fungi are heterotrophs, they acquire their food by absorbing dissolved molecules, growth is their means of mobility, except for spores, which may travel through the air or water. Fungi are the principal decomposers in ecological systems and this fungal group is distinct from the structurally similar myxomycetes and oomycetes. The discipline of biology devoted to the study of fungi is known as mycology, in the past, mycology was regarded as a branch of botany, although it is now known fungi are genetically more closely related to animals than to plants. Abundant worldwide, most fungi are inconspicuous because of the size of their structures. Fungi include symbionts of plants, animals, or other fungi and they may become noticeable when fruiting, either as mushrooms or as molds. Fungi perform a role in the decomposition of organic matter and have fundamental roles in nutrient cycling. Since the 1940s, fungi have been used for the production of antibiotics, Fungi are also used as biological pesticides to control weeds, plant diseases and insect pests. Many species produce bioactive compounds called mycotoxins, such as alkaloids and polyketides, the fruiting structures of a few species contain psychotropic compounds and are consumed recreationally or in traditional spiritual ceremonies. Fungi can break down manufactured materials and buildings, and become significant pathogens of humans, losses of crops due to fungal diseases or food spoilage can have a large impact on human food supplies and local economies. The fungus kingdom encompasses a diversity of taxa with varied ecologies, life cycle strategies. However, little is known of the biodiversity of Kingdom Fungi. Advances in molecular genetics have opened the way for DNA analysis to be incorporated into taxonomy, phylogenetic studies published in the last decade have helped reshape the classification within Kingdom Fungi, which is divided into one subkingdom, seven phyla, and ten subphyla. The English word fungus is directly adopted from the Latin fungus, used in the writings of Horace, a group of all the fungi present in a particular area or geographic region is known as mycobiota, e. g. the mycobiota of Ireland. Like plants, fungi grow in soil and, in the case of mushrooms, form conspicuous fruit bodies. The fungi are now considered a kingdom, distinct from both plants and animals, from which they appear to have diverged around one billion years ago. Fungi have membrane-bound cytoplasmic organelles such as mitochondria, sterol-containing membranes and they have a characteristic range of soluble carbohydrates and storage compounds, including sugar alcohols, disaccharides, and polysaccharides
7.
Triglyceride
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A triglyceride is an ester derived from glycerol and three fatty acids. Triglycerides are the constituents of body fat in humans and other animals. They are also present in the blood to enable the bidirectional transference of adipose fat and blood glucose from the liver, there are many different types of triglyceride, with the main division between saturated and unsaturated types. Saturated fats are saturated with hydrogen – all available places where hydrogen atoms could be bonded to carbon atoms are occupied and these have a higher melting point and are more likely to be solid at room temperature. Unsaturated fats have double bonds between some of the atoms, reducing the number of places where hydrogen atoms can bond to carbon atoms. These have a melting point and are more likely to be liquid at room temperature. Triglycerides are chemically tri esters of fatty acids and glycerol. Triglycerides are formed by combining glycerol with three fatty acid molecules, organic acids have a carboxyl group. Alcohols and organic acids join to form esters, the glycerol molecule has three hydroxyl groups. Each fatty acid has a carboxyl group, the chain lengths of the fatty acids in naturally occurring triglycerides vary, but most contain 16,18, or 20 carbon atoms. Bacteria, however, possess the ability to synthesise odd- and branched-chain fatty acids, as a result, ruminant animal fat contains odd-numbered fatty acids, such as 15, due to the action of bacteria in the rumen. Many fatty acids are unsaturated, some are polyunsaturated, most natural fats contain a complex mixture of individual triglycerides. Because of this, they melt over a range of temperatures. Cocoa butter is unusual in that it is composed of only a few triglycerides, derived from palmitic, oleic, and stearic acids in the 1-, 2-, the simplest triglycerides are those where the three fatty acids are identical. Their names indicate the fatty acid, stearin derived from acid, palmitin derived from palmitic acid. These compounds can be obtained as three forms or polymorphs, α, β, and β′ and these forms differ in terms of their melting points. If the first and third chain R and R″ are different, then the carbon atom is a chiral centre. The pancreatic lipase acts at the bond, hydrolysing the bond. In triglyceride form, lipids cannot be absorbed by the duodenum, fatty acids, monoglycerides, and some diglycerides are absorbed by the duodenum, once the triglycerides have been broken down
8.
Adipose tissue
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In biology, adipose tissue /ˈædᵻˌpoʊs/, body fat, or simply fat is a loose connective tissue composed mostly of adipocytes. Adipose tissue is derived from preadipocytes and its main role is to store energy in the form of lipids, although it also cushions and insulates the body. Far from being hormonally inert, adipose tissue has, in recent years, been recognized as an endocrine organ, as it produces hormones such as leptin, estrogen, resistin. The two types of tissue are white adipose tissue, which stores energy, and brown adipose tissue. The formation of adipose tissue appears to be controlled in part by the adipose gene, Adipose tissue – more specifically brown adipose tissue – was first identified by the Swiss naturalist Conrad Gessner in 1551. In humans, adipose tissue is located beneath the skin, around internal organs, in bone marrow, intermuscular, Adipose tissue is found in specific locations, which are referred to as adipose depots. Apart from adipocytes, which comprise the highest percentage of cells within adipose tissue, other types are present. SVF includes preadipocytes, fibroblasts, adipose tissue macrophages, and endothelial cells, Adipose tissue contains many small blood vessels. In the integumentary system, which includes the skin, it accumulates in the deepest level, around organs, it provides protective padding. Adipose depots in different parts of the body have different biochemical profiles, under normal conditions, it provides feedback for hunger and diet to the brain. Mice have eight major adipose depots, four of which are within the abdominal cavity, the mesenteric depot forms a glue-like web that supports the intestines and the omental depot and - when massive - extends into the ventral abdomen. Both the mesenteric and omental depots incorporate much lymphoid tissue as lymph nodes and milky spots, the layer of brown adipose tissue in this depot is often covered by a frosting of white adipose tissue, sometimes these two types of fat are hard to distinguish. The inguinal depots enclose the inguinal group of lymph nodes, minor depots include the pericardial, which surrounds the heart, and the paired popliteal depots, between the major muscles behind the knees, each containing one large lymph node. Of all the depots in the mouse, the depots are the largest. In an obese person, excess adipose tissue hanging downward from the abdomen is referred to as a panniculus, a panniculus complicates surgery of the morbidly obese individual. It may remain as an apron of skin if a severely obese person quickly loses large amounts of fat. This condition cannot be corrected through diet and exercise alone, as the panniculus consists of adipocytes and other supporting cell types shrunken to their minimum volume. Reconstructive surgery is one method of treatment, visceral fat or abdominal fat is located inside the abdominal cavity, packed between the organs
9.
Human
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Modern humans are the only extant members of Hominina tribe, a branch of the tribe Hominini belonging to the family of great apes. Several of these hominins used fire, occupied much of Eurasia and they began to exhibit evidence of behavioral modernity around 50,000 years ago. In several waves of migration, anatomically modern humans ventured out of Africa, the spread of humans and their large and increasing population has had a profound impact on large areas of the environment and millions of native species worldwide. Humans are uniquely adept at utilizing systems of communication for self-expression and the exchange of ideas. Humans create complex structures composed of many cooperating and competing groups, from families. Social interactions between humans have established a wide variety of values, social norms, and rituals. These human societies subsequently expanded in size, establishing various forms of government, religion, today the global human population is estimated by the United Nations to be near 7.5 billion. In common usage, the word generally refers to the only extant species of the genus Homo—anatomically and behaviorally modern Homo sapiens. In scientific terms, the meanings of hominid and hominin have changed during the recent decades with advances in the discovery, there is also a distinction between anatomically modern humans and Archaic Homo sapiens, the earliest fossil members of the species. The English adjective human is a Middle English loanword from Old French humain, ultimately from Latin hūmānus, the words use as a noun dates to the 16th century. The native English term man can refer to the species generally, the species binomial Homo sapiens was coined by Carl Linnaeus in his 18th century work Systema Naturae. The generic name Homo is a learned 18th century derivation from Latin homō man, the species-name sapiens means wise or sapient. Note that the Latin word homo refers to humans of either gender, the genus Homo evolved and diverged from other hominins in Africa, after the human clade split from the chimpanzee lineage of the hominids branch of the primates. The closest living relatives of humans are chimpanzees and gorillas, with the sequencing of both the human and chimpanzee genome, current estimates of similarity between human and chimpanzee DNA sequences range between 95% and 99%. The gibbons and orangutans were the first groups to split from the leading to the humans. The splitting date between human and chimpanzee lineages is placed around 4–8 million years ago during the late Miocene epoch, during this split, chromosome 2 was formed from two other chromosomes, leaving humans with only 23 pairs of chromosomes, compared to 24 for the other apes. There is little evidence for the divergence of the gorilla, chimpanzee. Each of these species has been argued to be an ancestor of later hominins
10.
Skeletal muscle
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Skeletal muscle is one of three major muscle types, the others being cardiac muscle and smooth muscle. It is a form of striated muscle tissue which is under the control of the somatic nervous system. Most skeletal muscles are attached to bones by bundles of collagen fibers known as tendons, a skeletal muscle refers to multiple bundles of cells called muscle fibers. The fibres and muscles are surrounded by connective tissue layers called fasciae, Muscle fibres, or muscle cells, are formed from the fusion of developmental myoblasts in a process known as myogenesis. Muscle fibres are cylindrical, and have more than one nucleus, Muscle fibers are in turn composed of myofibrils. The myofibrils are composed of actin and myosin filaments, repeated in units called sarcomeres, the sarcomere is responsible for the striated appearance of skeletal muscle, and forms the basic machinery necessary for muscle contraction. Connective tissue is present in all muscles as fascia, Muscle fibres are the individual contractile units within muscle. A single muscle such as the biceps contains many muscle fibres, another group of cells, the myosatellite cells are found between the basement membrane and the sarcolemma of muscle fibers. These cells are normally quiescent but can be activated by exercise or pathology to provide additional myonuclei for muscle growth or repair, development Individual muscle fibers are formed during development from the fusion of several undifferentiated immature cells known as myoblasts into long, cylindrical, multi-nucleated cells. Differentiation into this state is completed before birth with the cells continuing to grow in size thereafter. Microanatomy Skeletal muscle exhibits a distinctive banding pattern when viewed under the due to the arrangement of cytoskeletal elements in the cytoplasm of the muscle fibers. The principal cytoplasmic proteins are myosin and actin which are arranged in a unit called a sarcomere. The interaction of myosin and actin is responsible for muscle contraction, every single organelle and macromolecule of a muscle fiber is arranged to ensure form meets function. The cell membrane is called the sarcolemma with the known as the sarcoplasm. In the sarcoplasm are the myofibrils, the myofibrils are long protein bundles about 1 micrometer in diameter each containing myofilaments. Pressed against the inside of the sarcolemma are the unusual flattened myonuclei, between the myofibrils are the mitochondria. While the muscle fiber does not have a smooth endoplasmic reticulum, the sarcoplasmic reticulum surrounds the myofibrils and holds a reserve of the calcium ions needed to cause a muscle contraction. Periodically, it has dilated end sacs known as terminal cisternae and these cross the muscle fiber from one side to the other
11.
Concentration
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In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished, mass concentration, molar concentration, number concentration, the term concentration can be applied to any kind of chemical mixture, but most frequently it refers to solutes and solvents in solutions. The molar concentration has variants such as concentration and osmotic concentration. To concentrate a solution, one must add more solute, or reduce the amount of solvent, by contrast, to dilute a solution, one must add more solvent, or reduce the amount of solute. Unless two substances are fully miscible there exists a concentration at which no further solute will dissolve in a solution, at this point, the solution is said to be saturated. If additional solute is added to a solution, it will not dissolve, except in certain circumstances. Instead, phase separation will occur, leading to coexisting phases, the point of saturation depends on many variables such as ambient temperature and the precise chemical nature of the solvent and solute. Concentrations are often called levels, reflecting the mental schema of levels on the axis of a graph. There are four quantities that describe concentration, The mass concentration ρ i is defined as the mass of a constituent m i divided by the volume of the mixture V, ρ i = m i V. The molar concentration c i is defined as the amount of a constituent n i divided by the volume of the mixture V, c i = n i V, however, more commonly the unit mol/L is used. The number concentration C i is defined as the number of entities of a constituent N i in a divided by the volume of the mixture V, C i = N i V. The volume concentration ϕ i is defined as the volume of a constituent V i divided by the volume of the mixture V, ϕ i = V i V. Being dimensionless, it is expressed as a number, e. g.0.18 or 18%, several other quantities can be used to describe the composition of a mixture. Note that these should not be called concentrations, normality is defined as the molar concentration c i divided by an equivalence factor f e q. Since the definition of the equivalence factor depends on context, IUPAC, the SI unit for molality is mol/kg. The mole fraction x i is defined as the amount of a constituent n i divided by the amount of all constituents in a mixture n t o t, x i = n i n t o t. However, the deprecated parts-per notation is used to describe small mole fractions. The mole ratio r i is defined as the amount of a constituent n i divided by the amount of all other constituents in a mixture
12.
Basal metabolic rate
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Basal metabolic rate is the minimal rate of energy expenditure per unit time by endothermic animals at rest. It is reported in units per unit time ranging from watt to ml O2/min or joule per hour per kg body mass J/). Proper measurement requires a set of criteria be met. These criteria include being in a physically and psychologically undisturbed state, in a neutral environment. In bradymetabolic animals, such as fish and reptiles, the equivalent term standard metabolic rate is used and it follows the same criteria as BMR, but requires the documentation of the temperature at which the metabolic rate was measured. This makes BMR a variant of standard metabolic rate measurement that excludes the temperature data, Metabolism comprises the processes that the body needs to function. Basal metabolic rate is the amount of energy expressed in calories that a person needs to keep the body functioning at rest, some of those processes are breathing, blood circulation, controlling body temperature, cell growth, brain and nerve function, and contraction of muscles. Basal metabolic rate affects the rate that a person burns calories and ultimately whether that individual maintains, gains, the basal metabolic rate accounts for about 60 to 75% of the daily calorie expenditure by individuals. It is influenced by several factors, BMR typically declines by 1–2% per decade after age 20, mostly due to loss of fat-free mass, although the variability between individuals is high. The bodys generation of heat is known as thermogenesis and it can be measured to determine the amount of energy expended, BMR generally decreases with age and with the decrease in lean body mass. Increasing muscle mass has the effect of increasing BMR, but anaerobic exercise does increase resting energy consumption. Illness, previously consumed food and beverages, environmental temperature, BMR is measured under very restrictive circumstances when a person is awake. An accurate BMR measurement requires that the sympathetic nervous system not be stimulated. A more common measurement, which uses less strict criteria, is resting metabolic rate, BMR may be measured by gas analysis through either direct or indirect calorimetry, though a rough estimation can be acquired through an equation using age, sex, height, and weight. Basal metabolism is usually by far the largest component of total caloric expenditure, Exercise physiology textbooks have tables to show the conversion of height and body surface area as they relate to weight and basal metabolic values. The primary organ responsible for regulating metabolism is the hypothalamus, the hypothalamus is located on the diencephalon and forms the floor and part of the lateral walls of the third ventricle of the cerebrum. Through the ANS, the hypothalamus is the regulator of visceral activities, such as heart rate, movement of food through the gastrointestinal tract. When sufficient food or substrates have received and leptin is high, then the satiety center is stimulated
13.
Red blood cell
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RBCs take up oxygen in the lungs, or gills of fish, and release it into tissues while squeezing through the bodys capillaries. The cytoplasm of erythrocytes is rich in hemoglobin, a biomolecule that can bind oxygen and is responsible for the red color of the cells. In humans, mature red cells are flexible and oval biconcave disks. They lack a nucleus and most organelles, in order to accommodate maximum space for hemoglobin, they can be viewed as sacks of hemoglobin. Approximately 2.4 million new erythrocytes are produced per second in human adults, the cells develop in the bone marrow and circulate for about 100–120 days in the body before their components are recycled by macrophages. Each circulation takes about 60 seconds, approximately a quarter of the cells in the human body are red blood cells. Nearly half of the volume is red blood cells. Red blood cells are known as RBCs, red cells, red blood corpuscles, haematids. Packed red blood cells are red blood cells that have donated, processed. Almost all vertebrates, including all mammals and humans, have red blood cells, red blood cells are cells present in blood in order to transport oxygen. The only known vertebrates without red blood cells are the crocodile icefish, they live in very cold water. While they no longer use hemoglobin, remnants of hemoglobin genes can be found in their genome, oxygen can easily diffuse through the red blood cells cell membrane. Myoglobin, a related to hemoglobin, acts to store oxygen in muscle cells. The color of red cells is due to the heme group of hemoglobin. However, blood can appear bluish when seen through the vessel wall, pulse oximetry takes advantage of the hemoglobin color change to directly measure the arterial blood oxygen saturation using colorimetric techniques. Hemoglobin also has a high affinity for carbon monoxide, forming carboxyhemoglobin which is a very bright red in color. Flushed, confused patients with a reading of 100% on pulse oximetry are sometimes found to be suffering from carbon monoxide poisoning. The red blood cells of mammals are typically shaped as disks, flattened and depressed in the center, with a dumbbell-shaped cross section
14.
White blood cell
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White blood cells, also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and derived from multipotent cells in the bone known as hematopoietic stem cells. Leukocytes are found throughout the body, including the blood and lymphatic system, all white blood cells have nuclei, which distinguishes them from the other blood cells, the anucleated red blood cells and platelets. Types of white cells can be classified in standard ways. Two pairs of broadest categories classify them either by structure or by cell division lineage and these broadest categories can be further divided into the five main types, neutrophils, eosinophils, basophils, lymphocytes, and monocytes. These types are distinguished by their physical and functional characteristics, further subtypes can be classified, for example, among lymphocytes, there are B cells, T cells, and NK cells. The number of leukocytes in the blood is often an indicator of disease, the normal white cell count is usually between 4 × 109/L and 11 × 109/L. In the US this is expressed as 4,000 to 11,000 white blood cells per microliter of blood. They make up approximately 1% of the blood volume in a healthy adult. However, this 1% of the blood makes a difference to health. An increase in the number of leukocytes over the limits is called leukocytosis. It is normal when it is part of immune responses. It is occasionally abnormal, when it is neoplastic or autoimmune in origin, a decrease below the lower limit is called leukopenia. The name white blood cell derives from the appearance of a blood sample after centrifugation. White cells are found in the buff, a thin, typically white layer of nucleated cells between the red blood cells and the blood plasma. The scientific term leukocyte directly reflects its description and it is derived from the Greek roots leuk- meaning white and cyt- meaning cell. The buffy coat may sometimes be green if there are large amounts of neutrophils in the sample, all white blood cells are nucleated, which distinguishes them from the anucleated red blood cells and platelets. Types of leukocytes can be classified in standard ways, two pairs of broadest categories classify them either by structure or by cell lineage
15.
Brain
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The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. The brain is located in the head, usually close to the organs for senses such as vision. The brain is the most complex organ in a vertebrates body, in a human, the cerebral cortex contains approximately 15–33 billion neurons, each connected by synapses to several thousand other neurons. Physiologically, the function of the brain is to exert centralized control over the other organs of the body, the brain acts on the rest of the body both by generating patterns of muscle activity and by driving the secretion of chemicals called hormones. This centralized control allows rapid and coordinated responses to changes in the environment, the operations of individual brain cells are now understood in considerable detail but the way they cooperate in ensembles of millions is yet to be solved. This article compares the properties of brains across the range of animal species. It deals with the human brain insofar as it shares the properties of other brains, the ways in which the human brain differs from other brains are covered in the human brain article. Several topics that might be covered here are instead covered there because more can be said about them in a human context. The most important is brain disease and the effects of brain damage, the shape and size of the brain varies greatly between species, and identifying common features is often difficult. Nevertheless, there are a number of principles of architecture that apply across a wide range of species. Some aspects of structure are common to almost the entire range of animal species, others distinguish advanced brains from more primitive ones. The simplest way to gain information about brain anatomy is by visual inspection, Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior. Visually, the interior of the consists of areas of so-called grey matter, with a dark color, separated by areas of white matter. Further information can be gained by staining slices of tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations. It is also possible to examine the microstructure of brain tissue using a microscope, the brains of all species are composed primarily of two broad classes of cells, neurons and glial cells. Glial cells come in types, and perform a number of critical functions, including structural support, metabolic support, insulation. Neurons, however, are considered the most important cells in the brain. The property that makes neurons unique is their ability to send signals to target cells over long distances
16.
Blood
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Blood is a body fluid in humans and other animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells. In vertebrates, it is composed of blood cells suspended in blood plasma, plasma, which constitutes 55% of blood fluid, is mostly water, and contains dissipated proteins, glucose, mineral ions, hormones, carbon dioxide, and blood cells themselves. Albumin is the protein in plasma, and it functions to regulate the colloidal osmotic pressure of blood. The blood cells are red blood cells, white blood cells. The most abundant cells in blood are red blood cells. These contain hemoglobin, a protein, which facilitates oxygen transport by reversibly binding to this respiratory gas. In contrast, carbon dioxide is mostly transported extracellularly as bicarbonate ion transported in plasma, vertebrate blood is bright red when its hemoglobin is oxygenated and dark red when it is deoxygenated. Some animals, such as crustaceans and mollusks, use hemocyanin to carry oxygen, insects and some mollusks use a fluid called hemolymph instead of blood, the difference being that hemolymph is not contained in a closed circulatory system. In most insects, this blood does not contain oxygen-carrying molecules such as hemoglobin because their bodies are small enough for their system to suffice for supplying oxygen. Jawed vertebrates have an immune system, based largely on white blood cells. White blood cells help to resist infections and parasites, platelets are important in the clotting of blood. Arthropods, using hemolymph, have hemocytes as part of their immune system, Blood is circulated around the body through blood vessels by the pumping action of the heart. Medical terms related to blood often begin with hemo- or hemato- from the Greek word αἷμα for blood. In terms of anatomy and histology, blood is considered a form of connective tissue, given its origin in the bones. The average adult has a volume of roughly 5 litres. These blood cells consist of erythrocytes, leukocytes, and thrombocytes, by volume, the red blood cells constitute about 45% of whole blood, the plasma about 54. 3%, and white cells about 0. 7%. Whole blood exhibits non-Newtonian fluid dynamics, if all human hemoglobin were free in the plasma rather than being contained in RBCs, the circulatory fluid would be too viscous for the cardiovascular system to function effectively. One microliter of blood contains,4.7 to 6.1 million,4.2 to 5.4 million erythrocytes, Red blood cells contain the bloods hemoglobin, mature red blood cells lack a nucleus and organelles in mammals
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Blood sugar level
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The blood sugar concentration or blood glucose level is the amount of glucose present in the blood of a human or animal. The body naturally tightly regulates blood glucose levels as a part of metabolic homeostasis, with some exceptions, glucose is the primary source of energy for the bodys cells, and blood lipids are primarily a compact energy store. Glucose levels are usually lowest in the morning, before the first meal of the day, Blood sugar levels outside the normal range may be an indicator of a medical condition. A persistently high level is referred to as hyperglycemia, low levels are referred to as hypoglycemia, Diabetes mellitus is characterized by persistent hyperglycemia from any of several causes, and is the most prominent disease related to failure of blood sugar regulation. Intake of alcohol causes a surge in blood sugar. Also, certain drugs can increase or decrease glucose levels, the international standard way of measuring blood glucose levels are in terms of a molar concentration, measured in mmol/L. In the United States, West-Germany and other countries mass concentration is measured in mg/dL, since the molecular weight of glucose C6H12O6 is 180, the difference between the two units is a factor of 18, so that 1 mmol/L of glucose is equivalent to 18 mg/dL. Normal value ranges may vary slightly among different laboratories, many factors affect a persons blood sugar level. A bodys homeostatic mechanism, when operating normally, restores the blood sugar level to a range of about 4.4 to 6.1 mmol/L. The normal blood level for non-diabetics, should be between 3.9 and 5.5 mmol/L. The mean normal blood glucose level in humans is about 5.5 mmol/L, however, Blood sugar levels for those without diabetes and who are not fasting should be below 6.9 mmol/L. The blood glucose target range for diabetics, according to the American Diabetes Association, should be 5. 0–7.2 mmol/l before meals, and less than 10 mmol/L after meals. Despite widely variable intervals between meals or the consumption of meals with a substantial carbohydrate load, human blood glucose levels tend to remain within the normal range. However, shortly after eating, the glucose level may rise, in non-diabetics. The actual amount of glucose in the blood and body fluids is very small. In a healthy adult male of 75 kg with a volume of 5 liters. Part of the reason why this amount is so small is that, to maintain an influx of glucose into cells, in general, ranges of blood sugar in common domestic ruminants are lower than in many monogastric mammals. However this generalization does not extend to wild ruminants or camelids, a 90 percent reference interval for serum glucose of 26 to 181 mg/dL has been reported for captured mountain goats, where no effects of the pursuit and capture on measured levels were evident
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Starch
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Starch or amylum is a polymeric carbohydrate consisting of a large number of glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants as an energy store and it is the most common carbohydrate in human diets and is contained in large amounts in staple foods such as potatoes, wheat, maize, rice, and cassava. Pure starch is a white, tasteless and odorless powder that is insoluble in water or alcohol. It consists of two types of molecules, the linear and helical amylose and the branched amylopectin, depending on the plant, starch generally contains 20 to 25% amylose and 75 to 80% amylopectin by weight. Glycogen, the store of animals, is a more branched version of amylopectin. In industry, starch is converted into sugars, for example by malting and it is processed to produce many of the sugars used in processed foods. Dissolving starch in water gives wheatpaste, which can be used as a thickening, stiffening or gluing agent. The biggest industrial non-food use of starch is as an adhesive in the papermaking process, starch can be applied to parts of some garments before ironing, to stiffen them. The word starch is from a Germanic root with the strong, stiff. Amylum for starch is from the Greek αμυλον, amylon which means not ground at a mill, the root amyl is used in biochemistry for several compounds related to starch. Starch grains from the rhizomes of Typha as flour have been identified from grinding stones in Europe dating back to 30,000 years ago, starch grains from sorghum were found on grind stones in caves in Ngalue, Mozambique dating up to 100,000 years ago. Pure extracted wheat starch paste was used in Ancient Egypt possibly to glue papyrus, the extraction of starch is first described in the Natural History of Pliny the Elder around AD 77–79. Romans used it also in cosmetic creams, to powder the hair, persians and Indians used it to make dishes similar to gothumai wheat halva. Rice starch as surface treatment of paper has been used in production in China. In addition to starchy plants consumed directly,66 million tonnes of starch were being produced per year world-wide by 2008. In the EU this was around 8.5 million tonnes, with around 40% being used for applications and 60% for food uses. Most green plants use starch as their energy store, an exception is the family Asteraceae, where starch is replaced by the fructan inulin. In photosynthesis, plants use light energy to produce glucose from carbon dioxide, the glucose is used to make cellulose fibers, the structural component of the plant, or is stored in the form of starch granules, in amyloplasts
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Polymer
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A polymer is a large molecule, or macromolecule, composed of many repeated subunits. Because of their range of properties, both synthetic and natural polymers play an essential and ubiquitous role in everyday life. Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure, Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers. The units composing polymers derive, actually or conceptually, from molecules of low molecular mass. The term was coined in 1833 by Jöns Jacob Berzelius, though with a distinct from the modern IUPAC definition. The modern concept of polymers as covalently bonded macromolecular structures was proposed in 1920 by Hermann Staudinger, Polymers are studied in the fields of biophysics and macromolecular science, and polymer science. Polyisoprene of latex rubber is an example of a polymer. In biological contexts, essentially all biological macromolecules—i. e, proteins, nucleic acids, and polysaccharides—are purely polymeric, or are composed in large part of polymeric components—e. g. Isoprenylated/lipid-modified glycoproteins, where small molecules and oligosaccharide modifications occur on the polyamide backbone of the protein. The simplest theoretical models for polymers are ideal chains, Polymers are of two types, Natural polymeric materials such as shellac, amber, wool, silk and natural rubber have been used for centuries. A variety of natural polymers exist, such as cellulose. Most commonly, the continuously linked backbone of a used for the preparation of plastics consists mainly of carbon atoms. A simple example is polyethylene, whose repeating unit is based on ethylene monomer, however, other structures do exist, for example, elements such as silicon form familiar materials such as silicones, examples being Silly Putty and waterproof plumbing sealant. Oxygen is also present in polymer backbones, such as those of polyethylene glycol, polysaccharides. Polymerization is the process of combining many small molecules known as monomers into a covalently bonded chain or network, during the polymerization process, some chemical groups may be lost from each monomer. This is the case, for example, in the polymerization of PET polyester, the distinct piece of each monomer that is incorporated into the polymer is known as a repeat unit or monomer residue. Laboratory synthetic methods are divided into two categories, step-growth polymerization and chain-growth polymerization. However, some methods such as plasma polymerization do not fit neatly into either category
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Plant
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Plants are mainly multicellular, predominantly photosynthetic eukaryotes of the kingdom Plantae. The term is generally limited to the green plants, which form an unranked clade Viridiplantae. This includes the plants, conifers and other gymnosperms, ferns, clubmosses, hornworts, liverworts, mosses and the green algae. Green plants have cell walls containing cellulose and obtain most of their energy from sunlight via photosynthesis by primary chloroplasts and their chloroplasts contain chlorophylls a and b, which gives them their green color. Some plants are parasitic and have lost the ability to produce amounts of chlorophyll or to photosynthesize. Plants are characterized by sexual reproduction and alternation of generations, although reproduction is also common. There are about 300–315 thousand species of plants, of which the great majority, green plants provide most of the worlds molecular oxygen and are the basis of most of Earths ecologies, especially on land. Plants that produce grains, fruits and vegetables form humankinds basic foodstuffs, Plants play many roles in culture. They are used as ornaments and, until recently and in variety, they have served as the source of most medicines. The scientific study of plants is known as botany, a branch of biology, Plants are one of the two groups into which all living things were traditionally divided, the other is animals. The division goes back at least as far as Aristotle, who distinguished between plants, which generally do not move, and animals, which often are mobile to catch their food. Much later, when Linnaeus created the basis of the system of scientific classification. Since then, it has become clear that the plant kingdom as originally defined included several unrelated groups, however, these organisms are still often considered plants, particularly in popular contexts. When the name Plantae or plant is applied to a group of organisms or taxon. The evolutionary history of plants is not yet settled. Those which have been called plants are in bold, the way in which the groups of green algae are combined and named varies considerably between authors. Algae comprise several different groups of organisms which produce energy through photosynthesis, most conspicuous among the algae are the seaweeds, multicellular algae that may roughly resemble land plants, but are classified among the brown, red and green algae. Each of these groups also includes various microscopic and single-celled organisms
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Amylopectin
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Amylopectin /ˌæmᵻloʊˈpɛktᵻn/ is a water soluble polysaccharide and highly branched polymer of glucose found in plants. It is one of the two components of starch, the other being amylose, glucose units are linked in a linear way with α glycosidic bonds. Branching takes place with α bonds occurring every 24 to 30 glucose units, in contrast, amylose contains very few α bonds, or even none at all. This causes amylose to be hydrolyzed more slowly, but have higher density and its counterpart in animals is glycogen, which has the same composition and structure, but with more extensive branching that occurs every eight to 12 glucose units. Plants store starch within specialized organelles called amyloplasts, when energy is needed for cell work, the plant hydrolyzes the starch, releasing the glucose subunits. Humans and other animals that eat plant foods also use amylase, starch is made of about 70% amylopectin by weight, though it varies depending on the source. Amylopectin is highly branched, being formed of 2,000 to 200,000 glucose units and its inner chains are formed of 20-24 glucose subunits. Dissolved amylopectin starch has a tendency of retrogradation during storage. For this main reason, the starches are used in different applications mainly as a thickening agent or stabilizer
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Powder (substance)
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A powder is a dry, bulk solid composed of a large number of very fine particles that may flow freely when shaken or tilted. Powders are a special sub-class of granular materials, although the terms powder, in particular, powders refer to those granular materials that have the finer grain sizes, and that therefore have a greater tendency to form clumps when flowing. Granulars refers to the coarser granular materials that do not tend to form clumps except when wet, many manufactured goods come in powder form, such as flour, sugar, ground coffee, powdered milk, copy machine toner, gunpowder, cosmetic powders, and some pharmaceuticals. In nature, dust, fine sand and snow, volcanic ash, typically, a powder can be compacted or loosened into a vastly larger range of bulk densities than can a coarser granular material. When deposited by sprinkling, a powder may be very light, when vibrated or compressed it may become very dense and even lose its ability to flow. The bulk density of coarse sand, on the other hand, the clumping behavior of a powder arises because of the molecular Van der Waals force that causes individual grains to cling to one another. Actually, this force is present not just in powders, but in sand and gravel, only when the grains are very small and lightweight does the Van der Waals force become predominant, causing the material to clump like a powder. The cross-over size between flow conditions and stick conditions can be determined by simple experimentation, many other powder behaviors are common to all granular materials. These include segregation, stratification, jamming and unjamming, fragility, loss of energy, frictional shearing, compaction. Powders are transported in the atmosphere differently from a coarse granular material, for one thing, tiny particles have little inertia compared to the drag force of the gas that surrounds them, and so they tend to go with the flow instead of traveling in straight lines. For this reason, powders may be an inhalation hazard, larger particles cannot weave through the bodys defenses in the nose and sinus, but will strike and stick to the mucous membranes. The body then moves the mucous out of the body to expel the particles, the smaller particles on the other hand can travel all the way to the lungs from which they cannot be expelled. Serious and sometimes fatal diseases such as silicosis are a result from working with certain powders without adequate respiratory protection, also, if powder particles are sufficiently small, they may become suspended in the atmosphere for a very long time. Random motion of the air molecules and turbulence provide upward forces that may counteract the force of gravity. Coarse granulars, on the hand, are so heavy that they fall immediately back to the ground. Once disturbed, dust may form huge dust storms that cross continents and this actually explains why there is relatively little hazardous dust in the natural environment. Once aloft, the dust is likely to stay aloft until it meets water in the form of rain or a body of water. Then it sticks and is washed downstream to settle as mud deposits in a lake or sea
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Cytosol
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The cytosol or cytoplasmic matrix is the liquid found inside cells. It constitutes most of the intracellular fluid and it is separated into compartments by membranes. For example, the mitochondrial matrix separates the mitochondrion into many compartments, in the eukaryotic cell, the cytosol is within the cell membrane and is part of the cytoplasm, which also comprises the mitochondria, plastids, and other organelles, the cell nucleus is separate. The cytosol is thus a liquid matrix around the organelles, in prokaryotes, most of the chemical reactions of metabolism take place in the cytosol, while a few take place in membranes or in the periplasmic space. In eukaryotes, while many metabolic pathways occur in the cytosol. The cytosol is a mixture of substances dissolved in water. Although water forms the majority of the cytosol, its structure. The cytosol also contains amounts of macromolecules, which can alter how molecules behave. Although it was thought to be a simple solution of molecules. Such a soluble cell extract is not identical to the part of the cell cytoplasm and is usually called a cytoplasmic fraction. The term cytosol is now used to refer to the phase of the cytoplasm in an intact cell. This excludes any part of the cytoplasm that is contained within organelles, prior to this, other terms were used for the cell fluid, not always synonymously, as its nature was not very clear. The cytosol consists mostly of water, dissolved ions, small molecules, the majority of these non-protein molecules have a molecular mass of less than 300 Da. This mixture of molecules is extraordinarily complex, as the variety of molecules that are involved in metabolism is immense. For example, up to 200,000 different small molecules might be made in plants, although not all these will be present in the same species, or in a single cell. Estimates of the number of metabolites in single cells such as E. coli, most of the cytosol is water, which makes up about 70% of the total volume of a typical cell. The pH of the fluid is 7.4. While human cytosolic pH ranges between 7.0 -7.4, and is higher if a cell is growing
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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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Energy
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In physics, energy is the property that must be transferred to an object in order to perform work on – or to heat – the object, and can be converted in form, but not created or destroyed. The SI unit of energy is the joule, which is the transferred to an object by the mechanical work of moving it a distance of 1 metre against a force of 1 newton. Mass and energy are closely related, for example, with a sensitive enough scale, one could measure an increase in mass after heating an object. Living organisms require available energy to stay alive, such as the humans get from food. Civilisation gets the energy it needs from energy resources such as fuels, nuclear fuel. The processes of Earths climate and ecosystem are driven by the radiant energy Earth receives from the sun, the total energy of a system can be subdivided and classified in various ways. It may also be convenient to distinguish gravitational energy, thermal energy, several types of energy, electric energy. Many of these overlap, for instance, thermal energy usually consists partly of kinetic. Some types of energy are a mix of both potential and kinetic energy. An example is energy which is the sum of kinetic. Whenever physical scientists discover that a phenomenon appears to violate the law of energy conservation. Heat and work are special cases in that they are not properties of systems, in general we cannot measure how much heat or work are present in an object, but rather only how much energy is transferred among objects in certain ways during the occurrence of a given process. Heat and work are measured as positive or negative depending on which side of the transfer we view them from, the distinctions between different kinds of energy is not always clear-cut. In contrast to the definition, energeia was a qualitative philosophical concept, broad enough to include ideas such as happiness. The modern analog of this property, kinetic energy, differs from vis viva only by a factor of two, in 1807, Thomas Young was possibly the first to use the term energy instead of vis viva, in its modern sense. Gustave-Gaspard Coriolis described kinetic energy in 1829 in its modern sense, the law of conservation of energy was also first postulated in the early 19th century, and applies to any isolated system. It was argued for years whether heat was a physical substance, dubbed the caloric, or merely a physical quantity. In 1845 James Prescott Joule discovered the link between mechanical work and the generation of heat and these developments led to the theory of conservation of energy, formalized largely by William Thomson as the field of thermodynamics
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Triglycerides
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A triglyceride is an ester derived from glycerol and three fatty acids. Triglycerides are the constituents of body fat in humans and other animals. They are also present in the blood to enable the bidirectional transference of adipose fat and blood glucose from the liver, there are many different types of triglyceride, with the main division between saturated and unsaturated types. Saturated fats are saturated with hydrogen – all available places where hydrogen atoms could be bonded to carbon atoms are occupied and these have a higher melting point and are more likely to be solid at room temperature. Unsaturated fats have double bonds between some of the atoms, reducing the number of places where hydrogen atoms can bond to carbon atoms. These have a melting point and are more likely to be liquid at room temperature. Triglycerides are chemically tri esters of fatty acids and glycerol. Triglycerides are formed by combining glycerol with three fatty acid molecules, organic acids have a carboxyl group. Alcohols and organic acids join to form esters, the glycerol molecule has three hydroxyl groups. Each fatty acid has a carboxyl group, the chain lengths of the fatty acids in naturally occurring triglycerides vary, but most contain 16,18, or 20 carbon atoms. Bacteria, however, possess the ability to synthesise odd- and branched-chain fatty acids, as a result, ruminant animal fat contains odd-numbered fatty acids, such as 15, due to the action of bacteria in the rumen. Many fatty acids are unsaturated, some are polyunsaturated, most natural fats contain a complex mixture of individual triglycerides. Because of this, they melt over a range of temperatures. Cocoa butter is unusual in that it is composed of only a few triglycerides, derived from palmitic, oleic, and stearic acids in the 1-, 2-, the simplest triglycerides are those where the three fatty acids are identical. Their names indicate the fatty acid, stearin derived from acid, palmitin derived from palmitic acid. These compounds can be obtained as three forms or polymorphs, α, β, and β′ and these forms differ in terms of their melting points. If the first and third chain R and R″ are different, then the carbon atom is a chiral centre. The pancreatic lipase acts at the bond, hydrolysing the bond. In triglyceride form, lipids cannot be absorbed by the duodenum, fatty acids, monoglycerides, and some diglycerides are absorbed by the duodenum, once the triglycerides have been broken down
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Residue (chemistry)
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In chemistry residue is whatever remains or acts as a contaminant after a given class of events. Residue may be the material remaining after a process of preparation, separation, or purification, such as distillation, evaporation and it may also denote the undesired by-products of a chemical reaction. Toxic chemical residues, wastes or contamination from other processes, are a concern in food safety, for example, the U. S. Food and Drug Administration and the Canadian Food Inspection Agency have guidelines for detecting chemical residues that are possibly dangerous to consume. Residue may refer to an atom or a group of atoms that forms part of a molecule, in biochemistry and molecular biology, a residue refers to a specific monomer within the polymeric chain of a polysaccharide, protein or nucleic acid. One might say, This protein consists of 118 amino acid residues or The histidine residue is considered to be basic because it contains an imidazole ring. Note that a residue is different from a moiety, which, a residue might be one amino acid in a polypeptide or one monosaccharide in a starch molecule
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Glycosidic bond
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In chemistry, a glycosidic bond or glycosidic linkage is a type of covalent bond that joins a carbohydrate molecule to another group, which may or may not be another carbohydrate. A glycosidic bond is formed between the hemiacetal or hemiketal group of a saccharide and the group of some compound such as an alcohol. A substance containing a glycosidic bond is a glycoside, glycosidic bonds of the form discussed above are known as O-glycosidic bonds, in reference to the glycosidic oxygen that links the glycoside to the aglycone or reducing end sugar. In analogy, one also considers S-glycosidic bonds, where the oxygen of the bond is replaced with a sulfur atom. In the same way, N-glycosidic bonds, have the glycosidic oxygen replaced with nitrogen. Substances containing N-glycosidic bonds are known as glycosylamines. C-glycosyl bonds have the oxygen replaced by a carbon, the term C-glycoside is considered a misnomer by IUPAC and is discouraged. All of these modified glycosidic bonds have different susceptibility to hydrolysis, one distinguishes between α- and β-glycosidic bonds based on the relative stereochemistry of the anomeric position and the stereocenter furthest from C1 in the saccharide. An α-glycosidic bond is formed when both carbons have the same stereochemistry, whereas a β-glycosidic bond occurs when the two carbons have different stereochemistry. One complicating issue is that the alpha and beta conformations were originally defined based on the orientation of the major constituents in a Haworth projection. In this case, for D-sugars, a beta conformation would see the major constituent at each carbon drawn above the plane of the ring, for L-sugars, the definitions would then, necessarily, reverse. This is worth noting as these older definitions still permeate the literature, pharmacologists often join substances to glucuronic acid via glycosidic bonds in order to increase their water solubility, this is known as glucuronidation. Many other glycosides have important physiological functions, Nüchter et al. have shown a new approach to Fischer Glycosylation. Employing a microwave oven equipped with refluxing apparatus in a reactor with pressure bombs, Nüchter et al. were able to achieve 100% yield of α-. This method can be performed on a multi-kilogram scale, ondruschka, and W. Lautenschläger, Synthetic Communications 31,1277. Vishal Y Joshis method Joshi et al, d-glucose is first protected by forming the peracetate by addition of acetic anhydride in acetic acid, and then addition of hydrogen bromide which brominates at the 5-position. On addition of the alcohol ROH and lithium carbonate, the OR replaces the bromine and it was suggested by Joshi et al. that lithium acts as the nucleophile that attacks the carbon at the 5-position and through a transition state the alcohol is substituted for the bromine group. Glycoside hydrolases, are enzymes that break glycosidic bonds, glycoside hydrolases typically can act either on α- or on β-glycosidic bonds, but not on both
29.
Molar concentration
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A commonly used unit for molar concentration in chemistry is the molar, which is defined as the number of moles per litre. A solution with a concentration of 1 mol/L is equivalent to 1 molar, Molar concentration or molarity is most commonly expressed in units of moles of solute per litre of solution. Or more simply,1 molar =1 M =1 mole/litre, in thermodynamics the use of molar concentration is often not convenient, because the volume of most solutions slightly depends on temperature due to thermal expansion. This problem is resolved by introducing temperature correction factors, or by using a temperature-independent measure of concentration such as molality. The reciprocal quantity represents the dilution which can appear in Ostwalds law of dilution, in the International System of Units the base unit for molar concentration is mol/m3. However, this is impractical for most laboratory purposes and most chemical literature traditionally uses mol/dm3, or mol dm−3, the words millimolar and micromolar refer to mM and μM, respectively. The conversion to number concentration C i is given by, C i = c i ⋅ N A where N A is the Avogadro constant, approximately 6. 022×1023 mol−1. The conversion to mass concentration ρ i is given by, ρ i = c i ⋅ M i where M i is the mass of constituent i. A simpler relation can be obtained by considering the total molar concentration namely the sum of molar concentrations of all the components of the mixture, in an ionic solution, ionic strength is proportional to the sum of molar concentration of salts. The sum of products between these quantities equals one, ∑ i c i ⋅ V i ¯ =1 Molar concentration depends on the variation of the volume of the solution due mainly to thermal expansion. On small intervals of temperature the dependence is, c i = c i, T0 where c i, T0 is the concentration at a reference temperature. Molar and mass concentration have different values in space where diffusion happens, example 1, Consider 11.6 g of NaCl dissolved in 100 g of water. Example 2, Another typical task in chemistry is the preparation of 100 mL of a 2 mol/L solution of NaCl in water, example 3, The density of water is approximately 1000 g/L and its molar mass is 18.02 g/mol. Example 4, A typical protein in bacteria, such as E. coli, may have about 60 copies, and the volume of a bacterium is about 10 −15 L. For example, if a sodium carbonate solution has a concentration of c =1 mol/L. Molar Solution Concentration Calculator Experiment to determine the concentration of vinegar by titration
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Carbohydrate
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A carbohydrate is a biological molecule consisting of carbon, hydrogen and oxygen atoms, usually with a hydrogen–oxygen atom ratio of 2,1, in other words, with the empirical formula Cmn. This formula holds true for monosaccharides, some exceptions exist, for example, deoxyribose, a sugar component of DNA, has the empirical formula C5H10O4. Carbohydrates are technically hydrates of carbon, structurally it is accurate to view them as polyhydroxy aldehydes and ketones. The term is most common in biochemistry, where it is a synonym of saccharide, a group that includes sugars, starch, the saccharides are divided into four chemical groups, monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Monosaccharides and disaccharides, the smallest carbohydrates, are referred to as sugars. The word saccharide comes from the Greek word σάκχαρον, meaning sugar, while the scientific nomenclature of carbohydrates is complex, the names of the monosaccharides and disaccharides very often end in the suffix -ose. For example, grape sugar is the glucose, cane sugar is the disaccharide sucrose. Carbohydrates perform numerous roles in living organisms, polysaccharides serve for the storage of energy and as structural components. The 5-carbon monosaccharide ribose is an important component of coenzymes and the backbone of the genetic molecule known as RNA, the related deoxyribose is a component of DNA. Saccharides and their derivatives include many other important biomolecules that play key roles in the system, fertilization, preventing pathogenesis, blood clotting. In food science and in informal contexts, the term carbohydrate often means any food that is particularly rich in the complex carbohydrate starch or simple carbohydrates. Often in lists of information, such as the USDA National Nutrient Database, the term carbohydrate is used for everything other than water, protein, fat, ash. This will include chemical compounds such as acetic or lactic acid, carbohydrates are found in wide variety of foods. The important sources are cereals, potatoes, sugarcane, fruits, table sugar, bread, milk, starch and sugar are the important carbohydrates in our diet. Starch is abundant in potatoes, maize, rice and other cereals, sugar appears in our diet mainly as sucrose which is added to drinks and many prepared foods such as jam, biscuits and cakes. Glucose and fructose are found naturally in fruits and some vegetables. Glycogen is carbohydrate found in the liver and muscles, cellulose in the cell wall of all plant tissue is a carbohydrate. It is important in our diet as fibre which helps to maintain a healthy digestive system, formerly the name carbohydrate was used in chemistry for any compound with the formula Cm n
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Digestion
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Digestion is the breakdown of large insoluble food molecules into small water-soluble food molecules so that they can be absorbed into the watery blood plasma. In certain organisms, these substances are absorbed through the small intestine into the blood stream. Digestion is a form of catabolism that is divided into two processes based on how food is broken down, mechanical and chemical digestion. The term mechanical digestion refers to the breakdown of large pieces of food into smaller pieces which can subsequently be accessed by digestive enzymes. In chemical digestion, enzymes break down food into the small molecules the body can use. In the human system, food enters the mouth and mechanical digestion of the food starts by the action of mastication, a form of mechanical digestion. After undergoing mastication and starch digestion, the food will be in the form of a small and it will then travel down the esophagus and into the stomach by the action of peristalsis. Gastric juice in the stomach starts protein digestion, gastric juice mainly contains hydrochloric acid and pepsin. As these two chemicals may damage the stomach wall, mucus is secreted by the stomach, providing a slimy layer that acts as a shield against the effects of the chemicals. At the same time protein digestion is occurring, mechanical mixing occurs by peristalsis and this allows the mass of food to further mix with the digestive enzymes. After some time, the resulting liquid is called chyme. When the chyme is fully digested, it is absorbed into the blood, 95% of absorption of nutrients occurs in the small intestine. Water and minerals are reabsorbed back into the blood in the colon where the pH is slightly acidic about 5.6 ~6.9, some vitamins, such as biotin and vitamin K produced by bacteria in the colon are also absorbed into the blood in the colon. Waste material is eliminated from the rectum during defecation, there is a fundamental distinction between internal and external digestion. External digestion developed earlier in history, and most fungi still rely on it. In this process, enzymes are secreted into the environment surrounding the organism, where they break down an organic material, some organisms, including nearly all spiders, simply secrete biotoxins and digestive chemicals into the extracellular environment prior to ingestion of the consequent soup. Bacteria use several systems to obtain nutrients from other organisms in the environments, in a channel transupport system, several proteins form a contiguous channel traversing the inner and outer membranes of the bacteria. It is a system, which consists of only three protein subunits, the ABC protein, membrane fusion protein, and outer membrane protein
32.
Insulin
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Insulin is a peptide hormone produced by beta cells of the pancreatic islets. It regulates the metabolism of carbohydrates, fats and protein by promoting the absorption of, especially, glucose from the blood into fat, liver and skeletal muscle cells. In these tissues the absorbed glucose is converted into either glycogen via glycogenesis or fats via lipogenesis, or, in the case of the liver, Glucose production by the liver is strongly inhibited by high concentrations of insulin in the blood. Circulating insulin also affects the synthesis of proteins in a variety of tissues. It is therefore an anabolic hormone, promoting the conversion of small molecules in the blood into large molecules inside the cells, low insulin levels in the blood have the opposite effect by promoting widespread catabolism. Pancreatic beta cells are known to be sensitive to concentrations in the blood. When glucose concentrations in the blood are high, the pancreatic β cells secrete insulin into the blood, glucagon, through stimulating the liver to release glucose by glycogenolysis and gluconeogenesis, has the opposite effect of insulin. If pancreatic beta cells are destroyed by an reaction, insulin can no longer be synthesized or be secreted into the blood. This results in type 1 diabetes mellitus, which is characterized by high blood glucose concentrations. In type 2 diabetes mellitus the destruction of cells is less pronounced than in type 1 diabetes. Instead there is an accumulation of amyloid in the pancreatic islets, Type 2 diabetes is characterized by high rates of glucagon secretion into the blood which are unaffected by, and unresponsive to the concentration of glucose in the blood glucose. Insulin is still secreted into the blood in response to the blood glucose, as a result, the insulin levels, even when the blood sugar level is normal, are much higher than they are in healthy persons. There are a variety of treatment regimens, none of which is entirely satisfactory, when the pancreas’s capacity to secrete insulin can no longer keep the blood sugar level within normal bounds, insulin injections are given. The human insulin protein is composed of 51 amino acids, and has a mass of 5808 Da. It is a dimer of an A-chain and a B-chain, which are linked together by disulfide bonds, insulins structure varies slightly between species of animals. Insulin from animal sources differs somewhat in effectiveness from human insulin because of these variations, porcine insulin is especially close to the human version, and was widely used to treat type 1 diabetics before human insulin could be produced in large quantities by recombinant DNA technologies. The crystal structure of insulin in the state was determined by Dorothy Hodgkin. It is on the WHO Model List of Essential Medicines, the most important medications needed in a health system
33.
Hepatocyte
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A hepatocyte is a cell of the main parenchymal tissue of the liver. Hepatocytes make up 70-85% of the livers mass, the typical volume of a hepatocyte is 3.4 x 10−9 cm3. Smooth endoplasmic reticulum is abundant in hepatocytes, whereas most cells in the body have only small amounts, hepatocytes display an eosinophilic cytoplasm, reflecting numerous mitochondria, and basophilic stippling due to large amounts of rough endoplasmic reticulum and free ribosomes. Brown lipofuscin granules are observed together with irregular unstained areas of cytoplasm. The average life span of the hepatocyte is 5 months, they are able to regenerate, hepatocyte nuclei are round with dispersed chromatin and prominent nucleoli. Anisokaryosis is common and often reflects tetraploidy and other degrees of polyploidy, hepatocytes are organised into plates separated by vascular channels, an arrangement supported by a reticulin network. The hepatocyte plates are one cell thick in mammals and two cells thick in the chicken, sinusoids display a discontinuous, fenestrated endothelial cell lining. The endothelial cells have no basement membrane and are separated from the hepatocytes by the space of Disse, kupffer cells are scattered between endothelial cells, they are part of the reticuloendothelial system and phagocytose spent erythrocytes. Stellate cells store vitamin A and produce extracellular matrix and collagen, the hepatocyte is a cell in the body that manufactures serum albumin, fibrinogen, and the prothrombin group of clotting factors. It is the site for the synthesis of lipoproteins, ceruloplasmin, transferrin, complement. Hepatocytes manufacture their own proteins and intracellular enzymes. Synthesis of proteins is by the endoplasmic reticulum, and both the rough and smooth endoplasmic reticulum are involved in secretion of the proteins formed. The endoplasmic reticulum is involved in conjugation of proteins to lipid and carbohydrate moieties synthesized by, or modified within, the liver forms fatty acids from carbohydrates and synthesizes triglycerides from fatty acids and glycerol. Hepatocytes also synthesize apoproteins with which they then assemble and export lipoproteins, the liver is also the main site in the body for gluconeogenesis, the formation of carbohydrates from precursors such as alanine, glycerol, and oxaloacetate. The liver receives many lipids from the circulation and metabolizes chylomicron remnants. It also synthesizes cholesterol from acetate and further synthesizes bile salts, the liver is the sole site of bile salts formation. Hepatocytes have the ability to metabolize, detoxify, and inactivate exogenous compounds such as drugs, and insecticides, the drainage of the intestinal venous blood into the liver requires efficient detoxification of miscellaneous absorbed substances to maintain homeostasis and protect the body against ingested toxins. One of the functions of hepatocytes is to modify ammonia into urea for excretion
34.
Enzyme
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Enzymes /ˈɛnzaɪmz/ are macromolecular biological catalysts. Enzymes accelerate, or catalyze, chemical reactions, the molecules at the beginning of the process upon which enzymes may act are called substrates and the enzyme converts these into different molecules, called products. Almost all metabolic processes in the cell need enzymes in order to occur at rates fast enough to sustain life, the set of enzymes made in a cell determines which metabolic pathways occur in that cell. The study of enzymes is called enzymology, enzymes are known to catalyze more than 5,000 biochemical reaction types. Most enzymes are proteins, although a few are catalytic RNA molecules, enzymes specificity comes from their unique three-dimensional structures. Like all catalysts, enzymes increase the rate of a reaction by lowering its activation energy, some enzymes can make their conversion of substrate to product occur many millions of times faster. An extreme example is orotidine 5-phosphate decarboxylase, which allows a reaction that would take millions of years to occur in milliseconds. Chemically, enzymes are like any catalyst and are not consumed in chemical reactions, enzymes differ from most other catalysts by being much more specific. Enzyme activity can be affected by other molecules, inhibitors are molecules that decrease enzyme activity, many drugs and poisons are enzyme inhibitors. An enzymes activity decreases markedly outside its optimal temperature and pH, some enzymes are used commercially, for example, in the synthesis of antibiotics. French chemist Anselme Payen was the first to discover an enzyme, diastase and he wrote that alcoholic fermentation is an act correlated with the life and organization of the yeast cells, not with the death or putrefaction of the cells. In 1877, German physiologist Wilhelm Kühne first used the term enzyme, the word enzyme was used later to refer to nonliving substances such as pepsin, and the word ferment was used to refer to chemical activity produced by living organisms. Eduard Buchner submitted his first paper on the study of yeast extracts in 1897, in a series of experiments at the University of Berlin, he found that sugar was fermented by yeast extracts even when there were no living yeast cells in the mixture. He named the enzyme that brought about the fermentation of sucrose zymase, in 1907, he received the Nobel Prize in Chemistry for his discovery of cell-free fermentation. Following Buchners example, enzymes are usually named according to the reaction they carry out, the biochemical identity of enzymes was still unknown in the early 1900s. Sumner showed that the enzyme urease was a protein and crystallized it. These three scientists were awarded the 1946 Nobel Prize in Chemistry, the discovery that enzymes could be crystallized eventually allowed their structures to be solved by x-ray crystallography. This high-resolution structure of lysozyme marked the beginning of the field of structural biology, an enzymes name is often derived from its substrate or the chemical reaction it catalyzes, with the word ending in -ase
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Glycogen synthase
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Glycogen synthase is a key enzyme in glycogenesis, the conversion of glucose into glycogen. It is a glycosyltransferase that catalyses the reaction of UDP-glucose and n to yield UDP, in other words, this enzyme combines excess glucose residues one by one into a polymeric chain for storage as glycogen. Glycogen synthase concentration is highest in the bloodstream 30 to 60 minutes following intense exercise, much research has been done on glycogen degradation through studying the structure and function of glycogen phosphorylase, the key regulatory enzyme of glycogen degradation. On the other hand, much less is known about the structure of glycogen synthase, the crystal structure of glycogen synthase from Agrobacterium tumefaciens, however, has been determined at 2.3 A resolution. In its asymmetric form, glycogen synthase is found as a dimer and this structural property, among others, is shared with related enzymes, such as glycogen phosphorylase and other glycosyltransferases of the GT-B superfamily. Nonetheless, a more recent characterization of the Saccharomyces cerevisiae glycogen synthase crystal structure reveals that the dimers may actually interact to form a tetramer, since the structure of eukaryotic glycogen synthase is highly conserved among species, glycogen synthase likely forms a tetramer in humans as well. Glycogen synthase can be classified in two protein families. The first family, which is from mammals and yeast, is approximately 80 kDa, uses UDP-glucose as a sugar donor, the second family, which is from bacteria and plants, is approximately 50 kDA, uses ADP-glucose as a sugar donor, and is unregulated. Glycogen synthase catalyzes the conversion of the moiety of uridine diphosphate glucose into glucose to be incorporated into glycogen via an α glycosidic bond. However, since glycogen synthase requires an oligosaccharide primer as a glucose acceptor, in a recent study of transgenic mice, an overexpression of glycogen synthase and an overexpression of phosphatase both resulted in excess glycogen storage levels. This suggests that glycogen synthase plays an important biological role in regulating glycogen/glucose levels and is activated by dephosphorylation, in humans, there are two paralogous isozymes of glycogen synthase, The liver enzyme expression is restricted to the liver, whereas the muscle enzyme is widely expressed. Liver glycogen serves as a pool to maintain the blood glucose level during fasting. The role of muscle glycogen is as a reserve to provide energy during bursts of activity, meanwhile, the muscle isozyme plays a major role in the cellular response to long-term adaptation to hypoxia. Notably, hypoxia only induces expression of the muscle isozyme and not the liver isozyme, however, muscle-specific glycogen synthase activation may lead to excessive accumulation of glycogen, leading to damage in the heart and central nervous system following ischemic insults. Phosphorylation of glycogen synthase decreases its activity, the enzyme also cleaves the ester bond between the C1 position of glucose and the pyrophosphate of UDP itself. The control of glycogen synthase is a key step in regulating glycogen metabolism, glycogen synthase is directly regulated by glycogen synthase kinase 3, AMPK, protein kinase A, and casein kinase 2. Each of these protein kinases lead to phosphorylated and catalytically inactive glycogen synthase, the phosphorylation sites of glycogen synthase are summarized below. For enzymes in the GT3 family, these regulatory kinases inactivate glycogen synthase by phosphorylating it at the N-terminal of the 25th residue, glycogen synthase is also regulated by protein phosphatase 1, which activates glycogen synthase via dephosphorylation
36.
Postprandial
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Postprandial means after eating a meal while preprandial is before a meal. The term postprandial is used in many contexts, refers to activities performed after a meal, like drinking cocktails or smoking. A common use is in relation to blood sugar levels, which are normally measured 2 hours after and this is because blood glucose levels usually rise after a meal. The American Diabetes Association recommends a postprandial glucose level under 180 mg/dl, other uses of postprandial include, Postprandial dip is a mild decrease in blood sugar after eating a big meal. Postprandial hyperglycemia is high blood sugar following a meal and it can be evaluated in a postprandial glucose test. Postprandial hypotension is a decline in blood pressure which happens after eating a meal. Postprandial regurgitation is a symptom of rumination syndrome. Postprandial thermogenesis is heat production due to metabolism after a meal, Postprandial abdominal distension usually refers to bloating of the abdomen following a meal, especially a large one. It is generally harmless, but tends to be uncomfortable, instances of its sudden onset or prolonged duration can, however, be symptoms of certain severe adverse gastro-intestinal conditions such as irritable bowel disease. Postprandial abdominal distension is also a side effect of some medications. In the postprandium, there is digestion of food in the tract, followed by uptake and various metabolic processes. The postprandium is characterized by an activity of the parasympathetic nervous system
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Food energy
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Food energy is chemical energy that animals derive from food and molecular oxygen through the process of cellular respiration. Humans and other animals need a minimum intake of energy to sustain their metabolism. Foods are composed chiefly of carbohydrates, fats, proteins, alcohol, water, vitamins, carbohydrates, fats, proteins, alcohol, and water represent virtually all the weight of food, with vitamins and minerals making up only a small percentage of the weight. Organisms derive food energy from carbohydrates, fats and proteins as well as organic acids, polyols. Some diet components that provide little or no energy, such as water, minerals, vitamins, cholesterol. Water, minerals, vitamins, and cholesterol are not broken down, fiber, a type of carbohydrate, cannot be completely digested by the human body. Ruminants can extract energy from the respiration of cellulose because of bacteria in their rumens. Using the International System of Units, researchers measure energy in joules or in its multiples, the kilojoule is most often used for food-related quantities. An older metric system unit of energy, still used in food-related contexts, is the calorie, more precisely. Within the European Union, both the kilocalorie and kilojoule appear on nutrition labels, in many countries, only one of the units is displayed, in the US and Canada labels spell out the unit as calorie or as Calorie. Fats and ethanol have the greatest amount of energy per gram,37 and 29 kJ/g. Proteins and most carbohydrates have about 17 kJ/g, carbohydrates that are not easily absorbed, such as fiber, or lactose in lactose-intolerant individuals, contribute less food energy. Polyols and organic acids contribute 10 kJ/g and 13 kJ/g respectively, the amount of water, fat, and fiber in foods determines those foods energy density. Theoretically, one could measure food energy in different ways, using the Gibbs free energy of combustion, however, the convention is to use the heat of the oxidation reaction, with the water substance produced being in the liquid phase. The American chemist Wilbur Atwater worked these corrections out in the late 19th century, based on the work of Atwater, it became common practice to calculate energy content of foods using 4 kcal/g for carbohydrates and proteins and 9 kcal/g for lipids. The system was improved by Annabel Merrill and Bernice Watt of the USDA. Many governments require food manufacturers to label the energy content of their products, in the European Union, manufacturers of packaged food must label the nutritional energy of their products in both kilocalories and kilojoules, when required. In Australia and New Zealand, the energy must be stated in kilojoules
38.
Glycogen phosphorylase
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Glycogen phosphorylase is one of the phosphorylase enzymes. Glycogen phosphorylase catalyzes the rate-limiting step in glycogenolysis in animals by releasing glucose-1-phosphate from the terminal alpha-1, Glycogen phosphorylase is also studied as a model protein regulated by both reversible phosphorylation and allosteric effects. Glycogen phosphorylase breaks up glycogen into glucose subunits, n + Pi ⇌ n-1 + α-D-glucose-1-phosphate, Glycogen is left with one fewer glucose molecule, and the free glucose molecule is in the form of glucose-1-phosphate. In order to be used for metabolism, it must be converted to glucose-6-phosphate by the enzyme phosphoglucomutase, Glycogen phosphorylase can act only on linear chains of glycogen. Its work will come to a halt four residues away from α1-6 branch. In these situations, an enzyme is necessary, which will straighten out the chain in that area. After all this is done, glycogen phosphorylase can continue and this crevice connects the glycogen storage site to the active, catalytic site. Glycogen phosphorylase has a pyridoxal phosphate at each catalytic site, pyridoxal phosphate links with basic residues and covalently forms a Schiff base. There is also a proposed mechanism involving a positively charged oxygen in a half-chair conformation. The glycogen phosphorylase monomer is a protein, composed of 842 amino acids with a mass of 97.434 kDa in muscle cells. While the enzyme can exist as a monomer or tetramer. In mammals, the major isozymes of glycogen phosphorylase are found in muscle, liver, the brain type is predominant in adult brain and embryonic tissues, whereas the liver and muscle types are predominant in adult liver and skeletal muscle, respectively. The glycogen phosphorylase dimer has many regions of biological significance, including sites, glycogen binding sites, allosteric sites. First, the sites are relatively buried, 15Å from the surface of the protein. Perhaps the most important regulatory site is Ser14, the site of reversible phosphorylation very close to the subunit interface. The structural change associated with phosphorylation, and with the conversion of phosphorylase b to phosphorylase a, is the arrangement of the originally disordered residues 10 to 22 into α helices. This change increases phosphorylase activity up to 25% even in the absence of AMP, the allosteric site of AMP binding on muscle isoforms of glycogen phosphorylase are close to the subunit interface just like Ser14. AMP binding rotates the tower helices of the two subunits 50˚ relative to one another through greater organization and intersubunit interactions, the final, perhaps most curious site on the glycogen phosphorylase protein is the so-called glycogen storage site
39.
Glucagon
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Glucagon is a peptide hormone, produced by alpha cells of the pancreas. It works to raise the concentration of glucose in the bloodstream and it is also used as a medication to treat a number of health conditions. Its effect is opposite to that of insulin, which lowers the glucose, the pancreas releases glucagon when the concentration of glucose in the bloodstream falls too low. Glucagon causes the liver to convert stored glycogen into glucose, which is released into the bloodstream, high blood-glucose levels, on the other hand, stimulate the release of insulin. Insulin allows glucose to be taken up and used by insulin-dependent tissues, thus, glucagon and insulin are part of a feedback system that keeps blood glucose levels stable. Glucagon increases energy expenditure and is elevated under conditions of stress, Glucagon belongs to the secritin family of hormones. Glucagon generally elevates the concentration of glucose in the blood by promoting gluconeogenesis and glycogenolysis, glucose is stored in the liver in the form of the polysaccharide glycogen, which is a glucan. When glucagon binds to the receptors, the liver cells convert the glycogen into individual glucose molecules and release them into the bloodstream. As these stores become depleted, glucagon then encourages the liver, Glucagon turns off glycolysis in the liver, causing glycolytic intermediates to be shuttled to gluconeogenesis. Glucagon also regulates the rate of production through lipolysis. Glucagon induces lipolysis in humans under conditions of insulin suppression, Glucagon production appears to be dependent on the central nervous system through pathways yet to be defined. In invertebrate animals, eyestalk removal has been reported to affect glucagon production, excising the eyestalk in young crayfish produces glucagon-induced hyperglycemia. Glucagon binds to the receptor, a G protein-coupled receptor. The conformation change in the receptor activates G proteins, a protein with α, β. When the G protein interacts with the receptor, it undergoes a change that results in the replacement of the GDP molecule that was bound to the α subunit with a GTP molecule. This substitution results in the releasing of the α subunit from the β and γ subunits, the alpha subunit specifically activates the next enzyme in the cascade, adenylate cyclase. Adenylate cyclase manufactures cyclic adenosine monophosphate, which activates protein kinase A and this enzyme, in turn, activates phosphorylase kinase, which then phosphorylates glycogen phosphorylase b, converting it into the active form called phosphorylase a. Phosphorylase a is the responsible for the release of glucose-1-phosphate from glycogen polymers
40.
Glycogenolysis
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Glycogenolysis is the breakdown of glycogen to glucose-6-phosphate and glycogen. Glycogen branches are catabolized by the removal of glucose monomers via phosphorolysis. Glucose-1-phosphate is converted to glucose-6-phosphate by the enzyme phosphoglucomutase, glucose residues are phosphorolysed from branches of glycogen until four residues before a glucose that is branched with a α linkage. Glycogen debranching enzyme then transfers three of the remaining four units to the end of another glycogen branch. This exposes the α branching point, which is hydrolysed by α glucosidase, removing the final glucose residue of the branch as a molecule of glucose and this is the only case in which a glycogen metabolite is not glucose-1-phosphate. The glucose is subsequently phosphorylated to glucose-6-phosphate by hexokinase, Glycogenolysis takes place in the cells of the muscle and liver tissues in response to hormonal and neural signals. In particular, glycogenolysis plays an important role in the fight-or-flight response, in myocytes, glycogen degradation serves to provide an immediate source of glucose-6-phosphate for glycolysis, to provide energy for muscle contraction. In hepatocytes, the purpose of the breakdown of glycogen is for the release of glucose into the bloodstream for uptake by other cells. Glycogenolysis is regulated hormonally in response to blood sugar levels by glucagon and insulin, in myocytes, glycogen degradation may also be stimulated by neural signals. Parenteral administration of glucagon is a human medical intervention in diabetic emergencies when sugar cannot be given orally. It can also be administered intramuscularly, mutations at the liver enzyme glycogen phosphorylase lead to glycogen storage disease VI. Mutations at the enzyme glycogen phosphorylase lead to McArdles disease. Deficiencies at the glycogen debranching enzyme lead to glycogen storage disease III, glycogenesis The chemical logic of glycogen degradation at ufp. pt Glycogenolysis at the US National Library of Medicine Medical Subject Headings
. PMID 18840763. 
