1.
Micrograph
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A micrograph or photomicrograph is a photograph or digital image taken through a microscope or similar device to show a magnified image of an item. This is opposed to an image, which is at a scale that is visible to the naked eye. Micrography is the practice or art of using microscopes to make photographs, a micrograph contains extensive details that form the features of a microstructure. The neuropathologist Solomon C. Fuller designed and created the first photomicrograph in 1900, micrographs are widely used in all fields of microscopy. A light micrograph or photomicrograph is a micrograph prepared using an optical microscope, at a basic level, photomicroscopy may be performed simply by hooking up a regular camera to a microscope, thereby enabling the user to take photographs at reasonably high magnification. Roman Vishniac was a pioneer in the field of photomicroscopy, specializing in the photography of living creatures in full motion and he also made major developments in light-interruption photography and color photomicroscopy. An electron micrograph is a micrograph prepared using an electron microscope, however, the term electron micrograph is not used in electron microscopy. Digital micrography is a digital picture obtained either directly with a microscope or by scanning of a photomicrograph, digital micrographs are now commonly obtained using a USB microscope attached directly to a home computer or laptop. Today, an add-on three-in-one macro lens which has capability to take wide-angle, fish-eye and macro with 7x, 14x, micrographs usually have micron bars, or magnification ratios, or both. Magnification is a ratio between size of object on a picture and its real size, unfortunately, magnification is somewhat a misleading parameter. It depends on a size of a printed picture. Editors of journals and magazines routinely resize a figure to fit the page, a scale bar, or micron bar, is a bar of known length displayed on a picture. The bar can be used for measurements on a picture, when a picture is resized a bar is also resized. If a picture has a bar, the magnification can be easily calculated, ideally, all pictures destined for publication/presentation should be supplied with a scale bar, the magnification ratio is optional. All but one of the micrographs presented on this page do not have a bar, supplied magnification ratios are likely incorrect. The microscope has been used for scientific discovery. It has also linked to the arts since its invention in the 17th century. At first scientists used the microscope to view and draw objects not visible with the unaided eye, early adopters of the microscope, such as Robert Hooke and Antonie van Leeuwenhoek, were excellent illustrators
2.
Paper
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Paper is a thin material produced by pressing together moist fibres of cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets. It is a material with many uses, including writing, printing, packaging, cleaning. The modern pulp and paper industry is global, with China leading its production, the oldest known archaeological fragments of the immediate precursor to modern paper, date to the 2nd century BC in China. The pulp papermaking process is ascribed to Cai Lun, a 2nd-century AD Han court eunuch, with paper as an effective substitute for silk in many applications, China could export silk in greater quantity, contributing to a Golden Age. Because of papers introduction to the West through the city of Baghdad, in the 19th century, industrial manufacture greatly lowered its cost, enabling mass exchange of information and contributing to significant cultural shifts. In 1844, the Canadian inventor Charles Fenerty and the German F. G. Keller independently developed processes for pulping wood fibres, before the industrialisation of the paper production the most common fibre source was recycled fibres from used textiles, called rags. The rags were from hemp, linen and cotton, a process for removing printing inks from recycled paper was invented by German jurist Justus Claproth in 1774. Today this method is called deinking and it was not until the introduction of wood pulp in 1843 that paper production was not dependent on recycled materials from ragpickers. The word paper is etymologically derived from Latin papyrus, which comes from the Greek πάπυρος, although the word paper is etymologically derived from papyrus, the two are produced very differently and the development of the first is distinct from the development of the second. Papyrus is a lamination of natural plant fibres, while paper is manufactured from fibres whose properties have changed by maceration. To make pulp from wood, a chemical pulping process separates lignin from cellulose fibres and this is accomplished by dissolving lignin in a cooking liquor, so that it may be washed from the cellulose, this preserves the length of the cellulose fibres. Paper made from chemical pulps are also known as wood-free papers–not to be confused with paper, this is because they do not contain lignin. The pulp can also be bleached to produce paper, but this consumes 5% of the fibres, chemical pulping processes are not used to make paper made from cotton. There are three main chemical pulping processes, the process dates back to the 1840s and it was the dominant method extent before the second world war. Most pulping operations using the process are net contributors to the electricity grid or use the electricity to run an adjacent paper mill. Another advantage is that this process recovers and reuses all inorganic chemical reagents, soda pulping is another specialty process used to pulp straws, bagasse and hardwoods with high silicate content. There are two major mechanical pulps, thermomechanical pulp and groundwood pulp, in the TMP process, wood is chipped and then fed into steam heated refiners, where the chips are squeezed and converted to fibres between two steel discs. In the groundwood process, debarked logs are fed into grinders where they are pressed against rotating stones to be made into fibres
3.
Ultraviolet
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Ultraviolet is an electromagnetic radiation with a wavelength from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays. UV radiation constitutes about 10% of the light output of the Sun. It is also produced by electric arcs and specialized lights, such as lamps, tanning lamps. Consequently, the effects of UV are greater than simple heating effects. Suntan, freckling and sunburn are familiar effects of over-exposure, along with risk of skin cancer. Living things on dry land would be damaged by ultraviolet radiation from the Sun if most of it were not filtered out by the Earths atmosphere. More-energetic, shorter-wavelength extreme UV below 121 nm ionizes air so strongly that it is absorbed before it reaches the ground, Ultraviolet is also responsible for the formation of bone-strengthening vitamin D in most land vertebrates, including humans. The UV spectrum thus has both beneficial and harmful to human health. Ultraviolet rays are invisible to most humans, the lens in a human eye ordinarily filters out UVB frequencies or higher, and humans lack color receptor adaptations for ultraviolet rays. Under some conditions, children and young adults can see ultraviolet down to wavelengths of about 310 nm, near-UV radiation is visible to some insects, mammals, and birds. Small birds have a fourth color receptor for ultraviolet rays, this gives birds true UV vision, reindeer use near-UV radiation to see polar bears, who are poorly visible in regular light because they blend in with the snow. UV also allows mammals to see urine trails, which is helpful for animals to find food in the wild. The males and females of some species look identical to the human eye. Ultraviolet means beyond violet, violet being the color of the highest frequencies of visible light, Ultraviolet has a higher frequency than violet light. He called them oxidizing rays to emphasize chemical reactivity and to them from heat rays. The terms chemical and heat rays were eventually dropped in favour of ultraviolet and infrared radiation, in 1878 the effect of short-wavelength light on sterilizing bacteria was discovered. By 1903 it was known the most effective wavelengths were around 250 nm, in 1960, the effect of ultraviolet radiation on DNA was established. The discovery of the ultraviolet radiation below 200 nm, named vacuum ultraviolet because it is absorbed by air, was made in 1893 by the German physicist Victor Schumann
4.
Mitochondrion
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The mitochondrion is a double membrane-bound organelle found in all eukaryotic organisms. Some cells in multicellular organisms may however lack them. A number of organisms, such as microsporidia, parabasalids. To date, only one eukaryote, Monocercomonoides, is known to have completely lost its mitochondria, the word mitochondrion comes from the Greek μίτος, mitos, thread, and χονδρίον, chondrion, granule or grain-like. Mitochondria generate most of the supply of adenosine triphosphate, used as a source of chemical energy. Mitochondria are commonly between 0.75 and 3 μm in diameter but vary considerably in size and structure, unless specifically stained, they are not visible. Mitochondrial biogenesis is in turn temporally coordinated with these cellular processes, Mitochondria have been implicated in several human diseases, including mitochondrial disorders, cardiac dysfunction, heart failure and autism. The number of mitochondria in a cell can vary widely by organism, tissue, for instance, red blood cells have no mitochondria, whereas liver cells can have more than 2000, The organelle is composed of compartments that carry out specialized functions. These compartments or regions include the outer membrane, the space, the inner membrane. Although most of a cells DNA is contained in the cell nucleus, mitochondrial proteins vary depending on the tissue and the species. In humans,615 distinct types of protein have been identified from cardiac mitochondria, the mitochondrial proteome is thought to be dynamically regulated. The first observations of structures that probably represented mitochondria were published in the 1840s. Richard Altmann, in 1890, established them as cell organelles, the term mitochondria was coined by Carl Benda in 1898. Leonor Michaelis discovered that Janus green can be used as a stain for mitochondria in 1900. Benjamin F. Kingsbury, in 1912, first related them with cell respiration, in 1913, particles from extracts of guinea-pig liver were linked to respiration by Otto Heinrich Warburg, which he called grana. Warburg and Heinrich Otto Wieland, who had postulated a similar particle mechanism. It was not until 1925, when David Keilin discovered cytochromes, in the following years, the mechanism behind cellular respiration was further elaborated, although its link to the mitochondria was not known. The introduction of tissue fractionation by Albert Claude allowed mitochondria to be isolated from other cell fractions, in 1946, he concluded that cytochrome oxidase and other enzymes responsible for the respiratory chain were isolated to the mitchondria
5.
Mouse
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A mouse is a small rodent characteristically having a pointed snout, small rounded ears, a body-length scaly tail and a high breeding rate. The best known species is the common house mouse. It is also a popular pet, in some places, certain kinds of field mice are locally common. They are known to invade homes for food and shelter, domestic mice sold as pets often differ substantially in size from the common house mouse. This is attributable both to breeding and to different conditions in the wild, the most well known strain, the white lab mouse, has more uniform traits that are appropriate to its use in research. The American white-footed mouse and the mouse, as well as other common species of mouse-like rodents around the world. These, however, are in other genera, cats, wild dogs, foxes, birds of prey, snakes and even certain kinds of arthropods have been known to prey heavily upon mice. Nevertheless, because of its adaptability to almost any environment. Mice, in contexts, can be considered vermin which are a major source of crop damage, causing structural damage. In North America, breathing dust that has come in contact with mouse excrement has been linked to hantavirus, primarily nocturnal animals, mice compensate for their poor eyesight with a keen sense of hearing, and rely especially on their sense of smell to locate food and avoid predators. Mice build intricate burrows in the wild and these burrows typically have long entrances and are equipped with escape tunnels or routes. In at least one species, the design of a burrow is a genetic trait. Breeding onset is at about 50 days of age in females and males, although females may have their first estrus at 25–40 days. Mice are polyestrous and breed year round, ovulation is spontaneous, the duration of the estrous cycle is 4–5 days and estrus itself lasts about 12 hours, occurring in the evening. Vaginal smears are useful in timed matings to determine the stage of the estrous cycle, mating is usually nocturnal and may be confirmed by the presence of a copulatory plug in the vagina up to 24 hours post-copulation. The presence of sperm on a smear is also a reliable indicator of mating. Female mice housed together tend to go into anestrus and do not cycle, if exposed to a male mouse or the pheromones of a male mouse, most of the females will go into estrus in about 72 hours. This synchronization of the cycle is known as the Whitten effect
6.
Fluorescence microscope
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The specimen is illuminated with light of a specific wavelength which is absorbed by the fluorophores, causing them to emit light of longer wavelengths. The illumination light is separated from the much weaker emitted fluorescence through the use of an emission filter. Typical components of a microscope are a light source, the excitation filter, the dichroic mirror. The filters and the dichroic beamsplitter are chosen to match the spectral excitation and emission characteristics of the used to label the specimen. In this manner, the distribution of a fluorophore is imaged at a time. Multi-color images of types of fluorophores must be composed by combining several single-color images. Most fluorescence microscopes in use are epifluorescence microscopes, where excitation of the fluorophore and these microscopes are widely used in biology and are the basis for more advanced microscope designs, such as the confocal microscope and the total internal reflection fluorescence microscope. The majority of fluorescence microscopes, especially used in the life sciences, are of the epifluorescence design shown in the diagram. Light of the wavelength is focused on the specimen through the objective lens. Fluorescence microscopy requires intense, near-monochromatic, illumination which some widespread light sources, four main types of light source are used, including xenon arc lamps or mercury-vapor lamps with an excitation filter, lasers, supercontinuum sources, and high-power LEDs. In order for a sample to be suitable for fluorescence microscopy it must be fluorescent, there are several methods of creating a fluorescent sample, the main techniques are labelling with fluorescent stains or, in the case of biological samples, expression of a fluorescent protein. Alternatively the intrinsic fluorescence of a sample can be used, as a result, there is a diverse range of techniques for fluorescent staining of biological samples. Many fluorescent stains have been designed for a range of biological molecules, some of these are small molecules which are intrinsically fluorescent and bind a biological molecule of interest. Major examples of these are nucleic acid stains like DAPI and Hoechst and DRAQ5 and DRAQ7 which all bind the minor groove of DNA, others are drugs or toxins which bind specific cellular structures and have been derivatised with a fluorescent reporter. A major example of class of fluorescent stain is phalloidin which is used to stain actin fibres in mammalian cells. Immunofluorescence is a technique which uses the specific binding of an antibody to its antigen in order to label specific proteins or other molecules within the cell. A sample is treated with an antibody specific for the molecule of interest. A fluorophore can be conjugated to the primary antibody
7.
Staining
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Staining is an auxiliary technique used in microscopy to enhance contrast in the microscopic image. Stains and dyes are used in biology and medicine to highlight structures in biological tissues for viewing. Stains may be used to define and examine bulk tissues, cell populations, in biochemistry it involves adding a class-specific dye to a substrate to qualify or quantify the presence of a specific compound. Staining and fluorescent tagging can serve similar purposes, biological staining is also used to mark cells in flow cytometry, and to flag proteins or nucleic acids in gel electrophoresis. Simple staining is staining with only one stain/dye, there are various kinds of multiple staining, many of which are examples of counterstaining, differential staining, or both, including double staining and triple staining. In vivo staining is the process of dyeing living tissues—in vivo means in life, by causing certain cells or structures to take on contrasting colour, their form or position within a cell or tissue can be readily seen and studied. In vitro staining involves colouring cells or structures that have removed from their biological context. Certain stains are often combined to reveal more details and features than a single stain alone, combined with specific protocols for fixation and sample preparation, scientists and physicians can use these standard techniques as consistent, repeatable diagnostic tools. A counterstain is stain that makes cells or structures more visible, for example, crystal violet stains only Gram-positive bacteria in Gram staining. A safranin counterstain is applied that stains all cells, allowing identification of Gram-negative bacteria, while ex vivo, many cells continue to live and metabolize until they are fixed. Some staining methods are based on this property and those stains excluded by the living cells but taken up by the already dead cells are called vital stains. Those that enter and stain living cells are called supravital stains, however, these stains are eventually toxic to the organism, some more so than others. To achieve desired effects, the stains are used in very dilute solutions ranging from 1,5000 to 1,500000, note that many stains may be used in both living and fixed cells. The preparatory steps involved depend on the type of analysis planned, fixation–which may itself consist of several steps–aims to preserve the shape of the cells or tissue involved as much as possible. Sometimes heat fixation is used to kill, adhere, and alter the specimen so it accepts stains, most chemical fixatives generate chemical bonds between proteins and other substances within the sample, increasing their rigidity. Common fixatives include formaldehyde, ethanol, methanol, and/or picric acid, pieces of tissue may be embedded in paraffin wax to increase their mechanical strength and stability and to make them easier to cut into thin slices. Permeabilization involves treatment of cells with a mild surfactant and this treatment dissolves cell membranes, and allows larger dye molecules into the cells interior. Mounting usually involves attaching the samples to a microscope slide for observation
8.
Super-resolution microscopy
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Super-resolution microscopy is a form of light microscopy. Due to the diffraction of light, the resolution of conventional light microscopy is limited, Super-resolution techniques allow images to be taken with a higher resolution than the diffraction limit. However, the majority of techniques of importance in biological imaging fall into the functional category and these methods include STED, GSD, RESOLFT and SSIM. These methods include Super-resolution optical fluctuation imaging and all single-molecule localization methods such as SPDM, SPDMphymod, PALM, FPALM, on October 8,2014, the Nobel Prize in Chemistry was awarded to Eric Betzig, W. E. Moerner and Stefan Hell for the development of super-resolved fluorescence microscopy, some of the following information was gathered from a chemistry blogs review of sub-diffraction microscopy techniques Part I and Part II. For a review, see also reference, in 1986, the super-resolution optical microscope based on stimulated emission was patented by Okhonin. NORM microscopy is a method of optical near-field acquisition by a microscope through the observation of nanoparticles Brownian motion in an immersion liquid. NORM utilizes object surface scanning by stochastically moving nanoparticles, through the microscope, nanoparticles look like symmetric round spots. The spot width is equivalent to the point spread function and is defined by the microscope resolution, lateral coordinates of the given particle can be evaluated with a precision much higher than the resolution of the microscope. By collecting the information from many frames one can map out the field intensity distribution across the whole field of view of the microscope. In comparison with NSOM and ANSOM this method does not require any equipment for tip positioning and has a large field of view. Due to the number of scanning sensors one can get shorter time of image acquisition. A 4Pi microscope is a laser scanning microscope with an improved axial resolution. The typical value of 500–700 nm can be improved to 100–150 nm, the improvement in resolution is achieved by using two opposing objective lenses, both of which are focused to the same geometrical location. Also, the difference in path length through each of the two objective lenses is carefully aligned to be minimal. The solid angle Ω that is used for illumination and detection is increased, in this case the sample is illuminated and detected from all sides simultaneously. Up to now, the best quality in a 4Pi microscope was reached in conjunction with the STED principle in fixed cells, there is also the wide-field structured-illumination approach. SI enhances spatial resolution by collecting information from frequency space outside the observable region, the reverse FT returns the reconstructed image to a super-resolution image
9.
Banana
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The banana is an edible fruit – botanically a berry – produced by several kinds of large herbaceous flowering plants in the genus Musa. In some countries, bananas used for cooking may be called plantains, in contrast to dessert bananas. The fruit is variable in size, color and firmness, but is elongated and curved, with soft flesh rich in starch covered with a rind which may be green, yellow, red, purple. The fruits grow in clusters hanging from the top of the plant, almost all modern edible parthenocarpic bananas come from two wild species – Musa acuminata and Musa balbisiana. The scientific names of most cultivated bananas are Musa acuminata, Musa balbisiana, the old scientific name Musa sapientum is no longer used. Musa species are native to tropical Indomalaya and Australia, and are likely to have been first domesticated in Papua New Guinea. They are grown in 135 countries, primarily for their fruit, worldwide, there is no sharp distinction between bananas and plantains. Especially in the Americas and Europe, banana usually refers to soft, sweet, dessert bananas, particularly those of the Cavendish group, by contrast, Musa cultivars with firmer, starchier fruit are called plantains. In other regions, such as Southeast Asia, many kinds of banana are grown and eaten. The term banana is used as the common name for the plants which produce the fruit. This can extend to members of the genus Musa like the scarlet banana, pink banana. It can also refer to members of the genus Ensete, like the snow banana, both genera are classified under the banana family, Musaceae. The banana plant is the largest herbaceous flowering plant, all the above-ground parts of a banana plant grow from a structure usually called a corm. Plants are normally tall and fairly sturdy, and are mistaken for trees. Bananas grow in a variety of soils, as long as the soil is at least 60 cm deep, has good drainage and is not compacted. The leaves of plants are composed of a stalk and a blade. The base of the petiole widens to form a sheath, the tightly packed sheaths make up the pseudostem, the edges of the sheath meet when it is first produced, making it tubular. As new growth occurs in the centre of the pseudostem the edges are forced apart, cultivated banana plants vary in height depending on the variety and growing conditions
10.
Fluorescence
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Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence, in most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation. Fluorescent materials cease to glow immediately when the radiation source stops, unlike phosphorescence, Fluorescence also occurs frequently in nature in some minerals and in various biological states in many branches of the animal kingdom. An early observation of fluorescence was described in 1560 by Bernardino de Sahagún and it was derived from the wood of two tree species, Pterocarpus indicus and Eysenhardtia polystachya. The chemical compound responsible for this fluorescence is matlaline, which is the product of one of the flavonoids found in this wood. The name was derived from the fluorite, some examples of which contain traces of divalent europium. In a key experiment he used a prism to isolate ultraviolet radiation from sunlight, the specific frequencies of exciting and emitted light are dependent on the particular system. S0 is called the state of the fluorophore, and S1 is its first excited singlet state. A molecule in S1 can relax by various competing pathways and it can undergo non-radiative relaxation in which the excitation energy is dissipated as heat to the solvent. Excited organic molecules can also relax via conversion to a triplet state, relaxation from S1 can also occur through interaction with a second molecule through fluorescence quenching. Molecular oxygen is an extremely efficient quencher of fluorescence just because of its unusual triplet ground state, in most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation, this phenomenon is known as the Stokes shift. The emitted radiation may also be of the wavelength as the absorbed radiation. Molecules that are excited through light absorption or via a different process can transfer energy to a second sensitized molecule, the fluorescence quantum yield gives the efficiency of the fluorescence process. It is defined as the ratio of the number of photons emitted to the number of photons absorbed, Φ = Number of photons emitted Number of photons absorbed The maximum fluorescence quantum yield is 1.0, each photon absorbed results in a photon emitted. Compounds with quantum yields of 0.10 are still considered quite fluorescent, thus, if the rate of any pathway changes, both the excited state lifetime and the fluorescence quantum yield will be affected. Fluorescence quantum yields are measured by comparison to a standard, the quinine salt quinine sulfate in a sulfuric acid solution is a common fluorescence standard. The fluorescence lifetime refers to the time the molecule stays in its excited state before emitting a photon. This is an instance of exponential decay, various radiative and non-radiative processes can de-populate the excited state
11.
Chlorophyll
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Chlorophyll is any of several closely related green pigments found in cyanobacteria and the chloroplasts of algae and plants. Its name is derived from the Greek words χλωρός, chloros and φύλλον, chlorophyll is essential in photosynthesis, allowing plants to absorb energy from light. Chlorophyll absorbs light most strongly in the portion of the electromagnetic spectrum. Conversely, it is a poor absorber of green and near-green portions of the spectrum, chlorophyll molecules are specifically arranged in and around photosystems that are embedded in the thylakoid membranes of chloroplasts. Two types of chlorophyll exist in the photosystems of green plants, chlorophyll was first isolated and named by Joseph Bienaimé Caventou and Pierre Joseph Pelletier in 1817. Chlorophyll is vital for photosynthesis, which plants to absorb energy from light. Chlorophyll molecules are arranged in and around photosystems that are embedded in the thylakoid membranes of chloroplasts. In these complexes, chlorophyll serves two primary functions, the two currently accepted photosystem units are photosystem II and photosystem I, which have their own distinct reaction centres, named P680 and P700, respectively. These centres are named after the wavelength of their red-peak absorption maximum, the identity, function and spectral properties of the types of chlorophyll in each photosystem are distinct and determined by each other and the protein structure surrounding them. Once extracted from the protein into a solvent, these chlorophyll pigments can be separated into chlorophyll a, the function of the reaction center of chlorophyll is to absorb light energy and transfer it to other parts of the photosystem. The absorbed energy of the photon is transferred to an electron in a process called charge separation, the removal of the electron from the chlorophyll is an oxidation reaction. The chlorophyll donates the high energy electron to a series of molecular intermediates called a transport chain. The charged reaction center of chlorophyll is reduced back to its ground state by accepting an electron stripped from water. The electron that reduces P680+ ultimately comes from the oxidation of water into O2 and this reaction is how photosynthetic organisms such as plants produce O2 gas, and is the source for practically all the O2 in Earths atmosphere. Electron transfer reactions in the membranes are complex, however. NADPH is an agent used to reduce CO2 into sugars as well as other biosynthetic reactions. Thus, the other chlorophylls in the photosystem and antenna pigment proteins all cooperatively absorb, besides chlorophyll a, there are other pigments, called accessory pigments, which occur in these pigment–protein antenna complexes. Chlorophyll is a pigment, which is structurally similar to
12.
Antibody
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An antibody, also known as an immunoglobulin, is a large, Y-shaped protein produced mainly by plasma cells that is used by the immune system to neutralize pathogens such as bacteria and viruses. The antibody recognizes a molecule of the harmful agent, called an antigen. Each tip of the Y of an antibody contains a paratope that is specific for one particular epitope on an antigen, allowing these two structures to bind together with precision. Using this binding mechanism, an antibody can tag a microbe or a cell for attack by other parts of the immune system. Depending on the antigen, the binding may impede the process causing the disease or may activate macrophages to destroy the foreign substance. The ability of an antibody to communicate with the components of the immune system is mediated via its Fc region. The production of antibodies is the function of the humoral immune system. Antibodies are secreted by B cells of the immune system. In most cases, interaction of the B cell with a T helper cell is necessary to produce full activation of the B cell and, therefore, soluble antibodies are released into the blood and tissue fluids, as well as many secretions to continue to survey for invading microorganisms. Antibodies are glycoproteins belonging to the immunoglobulin superfamily and they constitute most of the gamma globulin fraction of the blood proteins. They are typically made of basic structural units—each with two heavy chains and two small light chains. There are several different types of heavy chains that define the five different types of crystallisable fragments that may be attached to the antigen-binding fragments. The five different types of Fc regions allow antibodies to be grouped into five isotypes, each Fc region of a particular antibody isotype is able to bind to its specific Fc Receptor, thus allowing the antigen-antibody complex to mediate different roles depending on which FcR it binds. The ability of an antibody to bind to its corresponding FcR is further modulated by the structure of the present at conserved sites within its Fc region. The ability of antibodies to bind to FcRs helps to direct the immune response for each different type of foreign object they encounter. For example, IgE is responsible for an allergic response consisting of mast cell degranulation, igEs Fab paratope binds to allergic antigen, for example house dust mite particles, while its Fc region binds to Fc receptor ε. The allergen-IgE-FcRε interaction mediates allergic signal transduction to induce conditions such as asthma and this region is known as the hypervariable region. Each of these variants can bind to a different antigen and this enormous diversity of antibody paratopes on the antigen-binding fragments allows the immune system to recognize an equally wide variety of antigens
