Biology questions and answers C

Biology C

What is C3 plant ?

The majority of photosynthetic plants that produce, as the initial steps of CO2 incorporation, a three-carbon compound, phosphoglyceric acid (PGA), as the first stable intermediate (CALVIN CYCLE). The PGA molecules are further phosphorylated (by ATP) and are reduced by NADPH to form phosphoglyceraldehyde (PGAL), which then serves as the starting material for the synthesis of glucose and fructose, which, when combined, make sucrose that travels through the plant. Velvetleaf (Abutilon theophrasti) is an example of a C3 plant.

What is C4 plant ?

A small number of plants that incorporate CO2 using a carboxylase for the CO2 capture, producing a four-carbon compound (carboxylic acid) as a stable intermediary in the first step of photosynthesis. C4 plants (e.g., corn) supply CO2 for the CALVIN CYCLE.

What is cage ?

An aggregate of molecules, generally in the condensed phase, that surround the fragments formed by thermal or photochemical dissociation of a species.

What is calcitonin ?

Calcitonin is a hormone produced by the thyroid gland that acts primarily on bone. It inhibits bone removal by osteoclasts and promotes bone formation by osteoblasts; lowers blood calcium levels.

What is calmodulin ?

A Ca2+ binding protein involved in muscular contraction.

What is calorie ?

An energy measurement unit; the amount of energy required to raise the temperature of 1 g of water by 1°C. A kilocalorie (1,000 calories) is used in food science to describe the energy content of food products.

What is calpain ?

A calcium-activated neutral protease.

What is Calvin cycle ?

The second major stage in photosynthesis after light reactions—discovered by chemist Melvin Calvin (1911–97)—whereby carbon molecules from CO2 are fixed into sugar (glucose) and mediated by the enzyme rubisco (ribulose-1-5-biphosphate carboxylase). It occurs in the stroma of chloroplasts. The Calvin cycle is also known as the dark reaction, as opposed to the first-stage light reactions.

What is CAM (crassulacean acid metabolism) ?

A metabolic adaptation of certain plants, particularly xerophytes (desert loving, e.g., succulents), in arid areas that allows them to take up CO2 at night, not during the day, store it as organic acid (malic), and release CO2 by decarboxylation of the acids for fixing into sugar. This reduces transpirational water loss during photosynthesis. The CALVIN CYCLE occurs during the day.

What is Cambrian explosion ?

A period about 530 million years ago (Cambrian age) when a large explosion of species, both in number and diversity, appeared on Earth. It lasted about 10 million years, and it is the first recorded evidence through the fossil record of larger and more complex life forms appearing.

What is Canadian shield ?

A geographic area of Canada centered around Hudson Bay and composed of 2- to 3billion-year-old igneous and metamorphic shield rock. It covers much of northern Canada.

What is cancer ?

Diseases in which abnormal cells divide and grow unchecked and can spread from the original site to other parts of the body; often fatal.

What is capillary ?

The smallest blood vessels in the circulatory system. Capillaries have thin walls that facilitate the transfer of oxygen and glucose into a cell and the removal of waste products such as carbon dioxide back out into the blood stream, to be carried away and taken out of the body via the lungs. They act as the bridge between the arteries, which carry blood away from the heart, and the veins, which carry blood back to the heart.

What is capsid ?

The outer protein coat or shell of a virus surrounding its genetic material. Also capsid bugs (capsidae), which number over 6,000 species and live on plants, sucking juice and damaging cultivated plants.

What is carbohydrate ?

A large class of compounds that contain carbon, hydrogen, and oxygen in a general formula of Cn(H2O)n. Classified from simple to complex, they form mono-, di-, tri-, poly-, and heterosaccharides. Examples include sugars (monosaccharide, di and polysaccharides), starches, and cellulose. Carbohydrates are used as an energy source by organisms, and most are formed by green plants and are obtained by animals via food intake.

What is carbon dioxide (CO2) ?

A colorless, odorless gas that makes up the fourth most abundant gas in the atmosphere. Used by plants in carbon fixation. Atmospheric CO2 has increased about 25 percent since the early 1800s due to burning fossil fuels and deforestation. Increased amounts of CO2 in the atmosphere enhance the greenhouse effect, blocking heat from escaping into space and contributing to the warming of Earth’s lower atmosphere and affecting the world’s biota. This is a major issue currently being debated by scientists around the world.

What is carbon fixation ?

The process by which carbon atoms from CO2 gas are incorporated into sugars. Carbon fixation occurs in the chloroplasts of green plants or any photosynthetic or chemoautotrophic organism.

What is carbonic anhydrase ?

A zinc-containing ENZYME (carbonate hydrolyase, carbonate dehydratase) that catalyzes the reversible decomposition of carbonic acid to carbon dioxide and water.

What is Carboniferous period ?

A geological time period (360 to 280 millions of years ago) during the middleto-late Paleozoic era. It is divided into the Pennsylvanian period (325 to 280 millions of years ago) and the Mississippian period (360 to 325 millions of years ago).

What is carbon monoxide (CO) ?

A colorless, odorless gas that is toxic.

What is carbon monoxide dehydrogenases ?

ENZYMEs that catalyze the oxidation of carbon monoxide to carbon dioxide. They contain IRON-SULFUR CLUSTERs and either nickel and zinc, or MOLYBDOPTERIN. Some nickel-containing enzymes are also involved in the synthesis of acetyl coenzyme A from CO2 and H2.

What is carbonyl group ?

A functional group with an oxygen atom double-bonded to a carbon atom, e.g., aldehydes (joined to at least one hydrogen atom) and ketones (carbonyl group is joined to alkyl groups or aryl groups).

What is carboplatin ?

A “second generation” platinum drug effective in cancer chemotherapy, named cis-diammine (cyclobutane-1,1-dicarboxylato)platinum(II). Carboplatin is less toxic than the “first generation” antitumor drug, CISPLATIN.

What is carboxyl group ?

A functional group that consists of a carbon atom joined to an oxygen atom by a double bond and to a hydroxyl group; present in all carboxylic acids.

What is carcinogen ?

Any substance that can produce cancer

What is cardiac muscle ?

One of the three muscle types (the others are skeletal and smooth); found in the walls of the heart, each rectangular heart muscle cell has one central nucleuslike smooth muscle, but it is striated like skeletal muscle. These cells are joined by intercalated discs, physical connections between the fibers of the myocardium, that relay each heartbeat through gap junctions (electrical synapses). Each strong and rhythmical contraction of the cardiac muscle is controlled by the autonomic nervous system and is involuntary.

What is cardiac output ?

The amount of blood that is pumped each minute from the left ventricle into the aorta or from the right ventricle into the pulmonary trunk.

What is cardiotech ?

A species radiolabeled with 99mTc with the formula [Tc(CNR)6]+(R=tert-butyl) known for IMAGING the heart after a heart attack.

What is cardiovascular system ?

The human circulatory system; the heart and all the vessels that transport blood to and from the heart.

What is carnivore ?

Any animal that eats the meat of other animals.

What is carotenoids ?

A large family of natural phytochemicals, accessory pigments found in plants (in chloroplasts) and animals that are composed of two small six-carbon rings connected by a carbon chain that must be attached to cell membranes. Their variety of colors absorb wavelengths that are not available to chlorophyll and so serve to transfer their captured energy from the sun to help in photosynthesis. Carotenoids color fruits and vegetables and give them their characteristic red, orange, and yellow colors and serve as antioxidants in human nutrition. Over 600 carotenoids are known.

What is carpal bones ?

Hand bones. The carpal bones include the navicular, lunate, pisiform, capitate, trapezium, trapezoid, hamate, and the triquetrum. They are arranged in two rows, the proximal (near the body) and the distal (near the fingers).

What is carpal tunnel ?

A small passage located below the wrist at the heel of the hand where the median nerve, the major nerve to the hand, as well as tendons that bend the fingers pass through.

What is carpel ?

The female reproductive part of the flower, including the ovary,style, and stigma.

Who was Carrel, Alexis ?

Carrel, Alexis (1873–1944) French Surgeon Alexis Carrel was born in Lyons, France, on June 28, 1873, to a businessman, also named Alexis Carrel, who died when his son was very young. Carrel was educated at home by his mother Anne Ricard and at St. Joseph School, in Lyons. He received a bachelor of letters degree in 1889 from the University of Lyons, a bachelor of science the following year, and, in 1900, his Ph.D. at the same university. He worked as prosector at the Lyons Hospital and taught anatomy and operative surgery at the university. By 1906, he was at the Rockefeller Institute for Medical Research, where he carried out most of his landmark experiments.

Influenced by the assassination by knife of the president of France in 1894, he dedicated himself to develop a way to suture blood vessels, which ironically he developed after he studied with a French embroidress who showed him how to do embroidery. His first attempt was made in France in 1902. He subsequently developed the triangulation technique of vascular suture. He won the Nobel Prize in physiology or medicine in 1912 for his work on vascular suture and the transplantation of blood vessels and organs.

During World War I, Carrel served as a major in the French army medical corps and helped devise a widely used method of treating war wounds, called the Carrel-Dakin method, a method of wound irrigation in which the wound is intermittently irrigated with Dakin’s solution, a germicidal fluid (no longer used).

Carrel’s researches were mainly concerned with experimental surgery and the transplantation of tissues and whole organs. As early as 1902, he published a technique for the end-to-end anastomosis (union) of blood vessels, and during the next few years he did every conceivable form of anastomosis, although many were not accepted until the 1950s. In 1908, he devised methods for the transplantation of whole organs and had tested kidney and heart transplantations as early as 1905. In 1910 he demonstrated that blood vessels could be kept for long periods in cold storage before they were used as transplants in surgery, and he also conducted aortocoronary bypass surgery, before the advent of anticoagulants.

In 1935, in collaboration with Charles Lindbergh, Carrel devised a machine for supplying a sterile respiratory system to organs removed from the body. Carrel was able to perform surgeries that showed that circulation, even in such vital organs as the kidneys, could be interrupted for as long as two hours without causing permanent damage. The cover of the June 13, 1938, Time magazine showed Charles Lindbergh and Alexis Carrel with the new perfusion pump.

His books, such as The Culture of Organs and Man, the Unknown, Treatment of Infected Wounds (with Georges Debelly), were important works. He died in Paris on November 5, 1944.

What is carrier ?

An individual who is heterozygous for a recessive disease-causing trait but who does not necessarily show any symptoms and can pass the mutant gene to offspring. If both parents are homozygous for the trait, the chance that a newborn child will be affected is one out of four.

What is carrier-linked prodrug (carrier prodrug) ?

A PRODRUG that contains a temporary linkage of a given active substance with a transient carrier group that provides improved physicochemical or pharmacokinetic properties and that can be easily removed in vivo, usually by a hydrolytic cleavage.

What is carrying capacity ?

A population’s maximum capacity within a habitat that a single species can maintain before the habitat degrades or becomes destroyed. While a species may go over the carrying capacity, the long-term viability of the habitat is destined to lessen or be depleted.

What is cartilage ?

A rubbery but firm and flexible shockabsorber tissue that cushions bones at the joints and can be found in other areas like the spine, throat, ears, and nose. Made up of cells called chondroblasts that secrete a cartilage matrix (containing cells called chondrocytes when surrounded by a matrix), an intracellular substance. Cartilage is covered by a membrane called perichondrium that serves for nutrition and growth of the cartilage. Osteoarthritis can occur when cartilage is worn away faster than it is replaced. The underlying bones then start to rub against each other.

What is cascade prodrug ?

A PRODRUG for which the cleavage of the carrier group becomes effective only after unmasking an activating group.

What is casparian strip ?

A band of suberin, a waxy substance that waterproofs the walls of each plant’s root cells; prevents and controls passive water and mineral uptake into the central vascular tube of roots (steles).

What is caste ?

Morphologically distinct individuals within a colony, e.g., ants, that are also behaviorally specialized such as queens, workers, soldiers, etc.

What is catabolic pathway ?

The process for taking large complex organic molecules and breaking them down into smaller ones, which release energy that can be used for metabolic processes.

What is catabolism ?

Reactions involving the breaking down of organic SUBSTRATES, typically by oxidative breakdown, to provide chemically available energy (e.g., adenosine triphosphate [ATP]) and/or to generate metabolic intermediates.

What is catabolite activator protein (CAP) ?

A protein that binds cyclic adenosine monophosphate (cAMP), a regulatory molecule, to DNA in organisms. When this interaction takes place, the gene promoter is made accessible to the enzyme RNA polymerase, and transcription of the gene can begin.

What is catalase ?

A HEME protein that catalyzes the DISPROPORTIONATION of dihydrogen peroxide to O2 and water. It also catalyzes the oxidation of other compounds, such as ethanol, by dihydrogen peroxide. A nonheme protein containing a dinuclear manganese CLUSTER with catalase activity is often called pseudocatalase.

What is catalyst ?

Any substance that speeds up a chemical reaction without itself being consumed by the reaction.

What is catalytic antibody (abzyme) ?

An ANTIBODY that catalyzes a chemical reaction analogous to an enzymatic reaction, such as an ester hydrolysis. It is obtained by using a hapten that mimics the transition state of the reaction.

What is cataract ?

The clouding of the natural lens of the eye or surrounding membrane, making it difficult to see.

What is catecholamine ?

A class of hormones, two of which are known to be important in a medical emergency. These are epinephrine and norepinephrine. Dopamine and dopa are also catecholamines. All the catecholamines stimulate high blood pressure and can trigger symptoms usually associated with threatening situations leading to a panic attack.

Epinephrine (adrenaline). A hormone released by the adrenal gland, which is the drug of choice for the treatment of anaphylaxis. Indeed, those who are allergic to insect stings and certain foods should always carry a self-injecting syringe of epinephrine.

Epinephrine increases the speed and force of heartbeats and, therefore, the work that can be done by the heart. It dilates the airways to improve breathing and narrows blood vessels in the skin and intestine so that an increased flow of blood reaches the muscles and allows them to cope with the demands of exercise. Usually treatment with this hormone stops an anaphylactic reaction. Epinephrine has been produced synthetically as a drug since 1900.

Norepinephrine (noradrenaline). A hormone released by the adrenal gland. Norepinephrine is released, along with epinephrine, from the adrenals and from nerves when heart failure takes place. These hormones are the first line of defense during any sudden stress. The release of these hormones cause the heart to pump faster, making up for the pumping problem caused by heart failure.

What is cation exchange ?

The ability of soils to attract and exchange cations with cations of soil solutions; high for clays and humus and low for sand.

What is catkin ?

A hanging group of unisexual flowers (either male or female) without petals, e.g., willows.

What is Caucasian ?

A member of the human race that is white skinned.

What is caudal ?

A fin, or direction toward a tail.

What is celiac disease (celiac sprue) ?

Celiac disease is a malabsorption disorder characterized by a permanent gluten-sensitive enteropathy resulting in malabsorption, failure to thrive, and other gastrointestinal manifestations. However, it should not be confused with a food allergy or hypersensitivity to food products.

Celiac disease is an inherited cell-mediated hypersensitivity involving a tissue-bound immune cell, often resulting in delayed reaction to a food allergen such as wheat, rye, oats, or barley. Gluten, a protein in these grains, is thought to be the offending agent. The disease has also been referred to as gluten enteropathy, gluten intolerance, gluten intolerant enteropathy, gluten-sensitive enteropathy, nontropical sprue, and wheat allergy.

The onset of the disease has no age restriction, but there are many hypotheses related to possible causative factors. In some adults, symptoms leading to a diagnosis of celiac sprue have been observed to appear following severe emotional stress, pregnancy, an operation, or a viral infection.

What is cell ?

The basic unit of life, capable of growing and multiplying. All living things are either single, independent cells or aggregates of cells. A cell is usually composed of cytoplasm and a nucleus, and it is surrounded by a membrane or wall. Cells can be categorized by the presence of specific cell surface markers called clusters of differentiation.

What is cell center (centrosome) ?

The organelle centrally located near the nucleus where the microtubules are organized and the location of the spindle pole during mitosis. A pair of centrioles, arrays of microtubules, are found in the center in the cells of animals.

What is cell cycle ?

The reproductive cycle of the eukaryotic cell: the orderly sequence of events (M, G1, S, and G2 phases) when a cell duplicates its contents and divides into two.

What is cell-cycle phases ?

The sequence of events that cells go through between mitotic divisions. The cycle is divided into gap 0 (G0), gap 1 (G1), synthesis phase (S) when DNA is replicated, Gap 2 (G2), and mitosis (M).

GO phase Period of time when the cell pauses in cell division between M (mitosis) and S (synthesis) phases. Normal cells in this phase have exactly one set of chromosome pairs.

G1 phase Period of time after mitosis but before S phase of the cell-division cycle; the cell is making preparations for DNA synthesis.

G2 phase Period of time after the S phase and before mitosis of the cell-division cycle. In this phase, the cells have duplicated their DNA and formed two sets of chromosome pairs, in preparation for division. G2 follows the S phase and precedes the M (mitosis) phase.

What is cell division ?

When two daughter cells are created from one cell.

What is cell fractionation ?

Separation of a cell’s individual subcellular components (membranes, nucleus, cytoplasm, mitochondria) by the use of centrifuges, which allows closer study of individual cellular components.

What is cell-mediated immunity (CMI; cellular immunity) ?

The branch of the immune system in which the reaction to foreign material is performed by specific defense cells (killer cells, macrophages, and other white blood cells) rather than antibodies.

What is cell membrane ?

A two-layered structure of material surrounding living cells. Most cell membranes have proteins, such as receptors and enzymes, embedded in them. The membrane holds the cell together, controls which substances go in or out, and maintains homeostasis.

What is cell plate ?

A membrane that forms in an area of the cytoplasm from the fusion of vesicles (which flatten) of a dividing plant cell during cytokinesis and which will develop into a new cell wall.

What is cellular differentiation ?

The process of embryonic cells developing into their destined specific forms and functions as an organism develops; a result of gene expression. The process by which different cells, all sharing the same DNA, are capable of performing different tasks.

What is cellular respiration ?

The process in which adenosine triphosphate (ATP) is created by metabolizing glucose and oxygen with the release of carbon dioxide. Occurs in the mitochondria of eukaryotes and in the cytoplasm of prokaryotes.

What is cellulose ?

A polysaccharide (polymer of glucose) that is found in the cell walls of plants. A fiber that is used in many commercial products like paper.

What is cell wall ?

A tough surrounding layer of a cell. In plant cells, it is formed of cellulose embedded in a polysaccharide-protein matrix and is composed of primary and secondary cell walls: the primary is flexible, while the secondary is more rigid. The cell wall provides structural support and protection.

Who was Celsius, Anders ?

Celsius, Anders (1701–1744) Swedish Astronomer, Physicist Anders Celsius was a Swedish astronomer, physicist, and mathematician who introduced the Celsius temperature scale that is used today by scientists in most countries. He was born in Uppsala, Sweden, a city that has produced six Nobel Prize winners. Celsius was born into a family of scientists, all originating from the province of Hälsingland. His father Nils Celsius was a professor of astronomy, as was his grandfather Anders Spole. His other grandfather, Magnus Celsius, was a professor of mathematics. Both grandfathers were at the university in Uppsala. Several of his uncles were also scientists.

Celsius’s important contributions include determining the shape and size of the Earth; gauging the magnitude of the stars in the constellation Aries; publication of a catalog of 300 stars and their magnitudes; observations on eclipses and other astronomical events; and a study revealing that the Nordic countries were slowly rising above the sea level of the Baltic. His most famous contribution falls in the area of temperature, and the one he is remembered most for is the creation of the Celsius temperature scale.

In 1742 he presented to the Swedish Academy of Sciences his paper, “Observations on Two Persistent Degrees on a Thermometer,” in which he presented his observations that all thermometers should be made on a fixed scale of 100 divisions (centigrade) based on two points: 0° for boiling water, and 100° for freezing water. He presented his argument on the inaccuracies of existing scales and calibration methods and correctly presented the influence of air pressure on the boiling point of water.

After his death, the scale that he designed was reversed, giving rise to the existing 0° for freezing and 100° for boiling water, instead of the reverse. It is not known if this reversal was done by his student Martin Stromer; or by botanist Carolus Linnaeus, who in 1745 reportedly showed the senate at Uppsala University a thermometer so calibrated; or if it was done by Daniel Ekström, who manufactured most of the thermometers used by both Celsius and Linneaus. However, Jean Christin from France made a centigrade thermometer with the current calibrations (0° freezing, 100° boiling) a year after Celsius and independent of him, and so he may therefore equally claim credit for the existing “Celsius” thermometers.

For years Celsius thermometers were referred to as “centigrade” thermometers. However, in 1948, the Ninth General Conference of Weights and Measures ruled that “degrees centigrade” would be referred to as “degrees Celsius” in his honor. The Celsius scale is still used today by most scientists.

Anders Celsius was secretary of the oldest Swedish scientific society, the Royal Society of Sciences in Uppsala, between 1725–44 and published much of his work through that organization, including a math book for youth in 1741. He died of tuberculosis on April 25, 1744, in Uppsala.

What is Celsius scale (centigrade scale) ?

A temperature scale with the range denoted by °C. The normal freezing point of water is 0°C, and the normal boiling point of water is 100°C. The scale was named after Anders Celsius, who proposed it in 1742 but designated the freezing point to be 100 and the boiling point to be 0 (reversed after his death).

What is Cenozoic era ?

Age of the mammals. The present geological era, beginning directly after the end of the Mesozoic era, 65 million years ago, and divided into the Quaternary and Tertiary periods.

What is central atom ?

The atom in a COORDINATION entity that binds other atoms or group of atoms (LIGANDs) to itself, thereby occupying a central position in the coordination entity.

What is central nervous system ?

That part of the nervous system that includes the brain and spinal cord. The brain receives and processes signals delivered through the spinal cord, where all signals are sent and received from all parts of the body, and in turn the brain then sends directions (signals) to the body.

What is centriole ?

A pair of short, cylindrical structures composed of nine triplet microtubules in a ring; found at the center of a centrosome; divides and organizes spindle fibers during MITOSIS and MEIOSIS.

What is centromere ?

A specialized area, the constricted region, near the center of a chromosome to which spindle fibers attach during cell division; the location where the two sister chromatids are joined to one another.

What is centrosome (microtubule organizing center) ?

The structural organizing center in cell cytoplasm, near the nucleus, where all microtubules originate; if folded it can become a centriole or a basal body for cilia and flagella.

What is cephalochordate ?

A chordate with no backbone (subphylum Cephalochordata), eg., lancelets.

What is cerebellum ?

A part of the vertebrate hindbrain; controls muscular coordination in both locomotion and balance.

What is cerebral cortex ?

The outer surface (3–5 mm) of the cerebrum and the sensory and motor nerves. It controls most of the functions that are controlled by the cerebrum (consciousness, the senses, the body’s motor skills, reasoning, and language) and is the largest and most complex part of the mammalian brain. The cortex is broken up into five lobes, each separated by an indentation called a fissure: the frontal lobe, the parietal lobe, the temporal lobe, the occipital lobe, and the insula. It is composed of six layers that have different densities and neuron types from the outermost to innermost: molecular layer, external granular layer, external pyramidal layer, internal granular layer, internal pyramidal layer, and the multiform layer. Vertical columns of neurons run through the layers.

What is cerebrum ?

The largest part of the brain; divided into two hemispheres (right and left) that are connected by nerve cells called the corpus callosum. It is the most recognized part of the brain and comprises 85 percent of its total weight. The cerebrum is where consciousness, the senses, the body’s motor skills, reasoning, and language take place.

What is ceruloplasmin ?

A copper protein present in blood plasma, containing TYPE 1, TYPE 2, and TYPE 3 COPPER centers, where the type 2 and type 3 are close together, forming a trinuclear copper CLUSTER.

Who was Chain, Ernst Boris ?

Chain, Ernst Boris (1906–1979) was German Biochemist Ernst Boris Chain was born on June 19, 1906, in Berlin, to Dr. Michael Chain, a chemist and industrialist. He was educated at the Luisen gymnasium, Berlin, with an interest in chemistry. He attended the Friedrich-Wilhelm University, Berlin, and graduated in chemistry in 1930. After graduation he worked for three years at the Charité Hospital, Berlin, on enzyme research. In 1933, after the rise of the Nazi regime in Germany, he left for England.

In 1935 he was invited to Oxford University, and in 1936 he became a demonstrator and lecturer in chemical pathology. In 1948 he was appointed scientific director of the International Research Centre for Chemical Microbiology at the Istituto Superiore di Sanità, Rome. He became professor of biochemistry at Imperial College, University of London, in 1961, serving in that position until 1973. Later, he became a pro fessor emeritus and a senior research fellow (1973–76) and a fellow (1978–79).

From 1935 to 1939 he worked on snake venoms, tumor metabolism, the mechanism of lysozyme action, and the invention and development of methods for biochemical microanalysis. In 1939 he began a systematic study of antibacterial substances produced by microorganisms and the reinvestigation of penicillin. Later he worked on the isolation and elucidation of the chemical structure of penicillin and other natural antibiotics.

With pathologist Howard Walter FLOREY (later Baron Florey), he isolated and purified penicillin and performed the first clinical trials of the antibiotic. For their pioneering work on penicillin Chain, Florey, and FLEMING shared the 1945 Nobel Prize in physiology or medicine.

Later his research topics included the carbohydrate– amino acid relationship in nervous tissue, a study of the mode of action of insulin, fermentation technology, 6-aminopenicillanic acid and penicillinase-stable penicillins, lysergic acid production in submerged culture, and the isolation of new fungal metabolites.

From 1935 to 1939 he worked on snake venoms, tumor metabolism, the mechanism of lysozyme action, and the invention and development of methods for biochemical microanalysis. In 1939 he began a systematic study of antibacterial substances produced by microorganisms and the reinvestigation of penicillin. Later he worked on the isolation and elucidation of the chemical structure of penicillin and other natural antibiotics.

With pathologist Howard Walter FLOREY (later Baron Florey), he isolated and purified penicillin and performed the first clinical trials of the antibiotic. For their pioneering work on penicillin Chain, Florey, and FLEMING shared the 1945 Nobel Prize in physiology or medicine.

Later his research topics included the carbohydrate– amino acid relationship in nervous tissue, a study of the mode of action of insulin, fermentation technology, 6-aminopenicillanic acid and penicillinase-stable penicillins, lysergic acid production in submerged culture, and the isolation of new fungal metabolites.

Chain was the author of many scientific papers and a contributor to important monographs on penicillin and antibiotics, and was the recipient of many awards including being knighted in 1969. He died on August 12, 1979.

What is channels ?

Transport proteins that act as gates to control the movement of sodium and potassium ions across the plasma membrane of a nerve cell.

What is chaparral ?

Dense vegetation of fire-adapted thick shrubs and low trees living in areas of little water and extreme summer heat in the coastal and mountainous regions of California. Similar community types exist in the coastal and mountainous regions of South Africa (fynbos), Chile (matorral), Spain (maquis), Italy (macchia), and Western Australia (kwongan). Also referred to as coastal sagebrush.

What is chaperonin ?

A member of the set of molecular chaperones, located in different organelles of the cell and involved either in transport of proteins through BIOMEMBRANEs (by unfolding and refolding the proteins) or in assembling newly formed POLYPEPTIDEs.

What is character ?

A synonym for a trait in TAXONOMY.

What is character displacement ?

The process whereby two closely related species interact in such a way, such as intense competition between species, as to cause one or both to diverge still further. This is most often apparent when the two species are found together in the same environment, e.g., large and small mouth bass.

What is charge-transfer complex ?

An aggregate of two or more molecules in which charge is transferred from a donor to an acceptor.

What is charge-transfer transition ?

An electronic transition in which a large fraction of an electronic charge is transferred from one region of a molecular entity, called the electron donor, to another, called the electron acceptor (intramolecular charge transfer), or from one molecular entity to another (intermolecular charge transfer).

What is chelation ?

Chelation involves COORDINATION of more than one sigma-electron pair donor group from the same LIGAND to the same CENTRAL ATOM. The number of coordinating groups in a single chelating ligand is indicated by the adjectives didentate, tridentate, tetradentate, etc.

What is chelation therapy ?

The judicious use of chelating (metal binding) agents for the removal of toxic amounts of metal ions from living organisms. The metal ions are sequestered by the chelating agents and are rendered harmless or excreted. Chelating agents such as 2,3-dimercaptopropan-1-ol, ethylenediaminetetraacetic acid, DESFERRIOXAMINE, and D-penicillamine have been used effectively in chelation therapy for arsenic, lead, iron, and copper, respectively.

What is chemical equilibrium ?

The condition when the forward and reverse reaction rates are equal and the concentrations of the products remain constant. Called the law of chemical equilibrium.

What is chemiosmosis ?

A method of making ATP that uses the electron transport chain and a proton pump to transfer hydrogen protons across certain membranes and then utilize the energy created to add a phosphate group (phosphorylate) to ADP, creating ATP as the end product.

What is chemoautotroph (chemolithotroph) ?

An organism that uses carbon dioxide as its carbon source and obtains energy by oxidizing inorganic substances.

What is chemoheterotroph ?

Any organism that derives its energy by oxidizing organic substances for both a carbon source and energy.

What is chemoreceptor ?

A sense organ, cell, or structure that detects and responds to chemicals in the air or in solution.

What is chemotherapy ?

The treatment of killing cancer cells by using chemicals.

What is chiasma ?

The x-shaped point or region where homologous chromatids have exchanged genetic material through crossing over during MEIOSIS. The term is also applied to the site where some optic nerves from each eye cross over to the opposite side of the brain, forming the optic tract.

What is chigger ?

Red, hairy, very small mites (arachnids) of the family Trombiculidae, such as Trombicula alfreddu chigger gesi and T. splendens Ewing. Also called jiggers and redbugs. Chiggers cause skin irritation in humans and dermatitis in animals.

What is chigoe flea ?

A flea (Tunga penetrans) that attacks bare feet and causes nodular swellings and ulcers around toenails, as well as between the toes and the sole.

What is chirality ?

A term describing the geometric property of a rigid object (or spatial arrangement of points or atoms) that is nonsuperimposable on its mirror image; such an object has no symmetry elements of the second kind (a mirror plane, a center of inversion, a rotation reflection axis). If the object is superimposable on its mirror image, the object is described as being achiral.

What is chi-square test ?

A statistical exercise that compares the frequencies of various kinds or categories of items in a random sample with the frequencies that are expected if the population frequencies are as hypothesized by the researcher.

What is chitin ?

The long-chained structural polysaccharide found in the exoskeleton of invertebrates such as crustaceans, insects, and spiders and in some cell walls of fungi. A beta-1,4-linked homopolymer of N-acetyl-Dglucosamine.

What is chlamydospore ?

A thick-walled asexual resting spore of certain fungi assuming a role for survival in soil or in decaying crop debris from year to year.

What is chlorin ?

In organic chemistry, it is an unsubstituted, reduced PORPHYRIN with two nonfused saturated carbon atoms (C-2, C-3) in one of the pyrrole rings.

What is chlorophyll ?

Part of the photosynthetic systems in green plants. Generally speaking, it can be considered as a magnesium complex of a PORPHYRIN in which a double bond in one of the pyrrole rings (17-18) has been reduced. A fused cyclopentanone ring is also present (positions 13-14-15). In the case of chlorophyll a, the substituted porphyrin ligand further contains four methyl groups in positions 2, 7, 12, and 18, a vinyl group in position 3, an ethyl group in position 8, and a –(CH2)2CO2R group (R=phytyl, (2E)-(7R, 11R)-3,7, 11,15-tetramethylhexadec-2-en-1-yl) in position 17. In chlorophyll b, the group in position 7 is a –CHO group. In bacteriochlorophyll a, the porphyrin ring is further reduced (7-8), and the group in position 3 is now a –COCH3 group. In addition, in bacteriochlorophyll b, the group in position 8 is a =CHCH3 group.

What is chloroplast ?

The double membrane organelle of eukaryotic photosynthesis; contains enzymes and pigments that perform photosynthesis.

What is cholera ?

An acute infection of the small intestines by Vibrio cholerae that is transmitted by ingesting fecalcontaminated water or food, or raw or undercooked seafood. Symptoms include diarrhea, abdominal cramps, nausea, vomiting, and severe dehydration. Endemic to India, Africa, the Mediterranean, South and Central America, Mexico, and the United States. Highly infectious disease that can be fatal, but there is a vaccine against it.

What is cholesterol ?

A soft, waxy, fat-soluble steroid formed by the liver and a natural component of fats in the bloodstream (as lipoproteins); most common steroid in the human body and used by all cells in permeability of their membranes. It is used in the formation of many products such as bile acids, vitamin D, progesterone, estrogens, and androgens. In relation to human health, there is the high-density “good” cholesterol (HDL), which protects the heart, and the low-density “bad” cholesterol (LDL), which causes heart disease and other problems.

What is chondrichthyes ?

Cartilaginous fishes; internal skeletons are made of cartilage and reinforced by small bony plates, while the external body is covered with hooklike scales. There are over 900 species in two subclasses, Elasmobranchii (sharks, skates, and rays) and Holocephali (chimaeras).

What is chondrin ?

A substance that forms the matrix of cartilage, along with collagen; formed by chondrocytes.

What is chordate ?

One of the most diverse and successful animal groups. The phylum Chordata includes fish, amphibians, reptiles, birds, mammals, and two invertebrates (tunicates and lancelets). Characterized by having at various times of their life a notochord (primitive spine, skeletal rod), pharyngeal slits, and hollow nerve cord ending in the brain area; usually have a head, a tail, and a digestive system, with an opening at both ends of the body. Their bodies are elongate and bilaterally symmetrical. Includes the hemichordates (vertebrates), cephalochordates (e.g., amphioxus), and urochordates (e.g., sea squirts).

What is chorion ?

One of the four extraembryonic membranes, along with AMNION, YOLK SAC, and ALLANTOIS. It contributes to the formation of the PLACENTA in mammals; outermost membrane.

What is chorionic villus sampling ?

A prenatal diagnosis technique that takes a small sample of tissue from the placenta and tests for certain birth defects. This is an early detection test, as it can be performed 10 to 12 weeks after a woman’s last menstrual cycle.

What is chromatin ?

The combination of DNA and proteins that make up the chromosomes of eukaryotes. Exists as long, thin fibers when cells are not dividing; not visible until cell division takes place.

What is chromatography ?

A method of chemical analysis where a compound is separated by allowing it to migrate over an absorbent material, revealing each of the constituent chemicals as separate layers.

What is Chromista ?

Brown algae, diatoms, and golden algae, placed together under a new proposed kingdom name.

What is chromophore ?

That part of a molecular entity consisting of an atom or group of atoms in which the electronic transition responsible for a given spectral band is approximately localized.

What is chromosome ?

The self-replicating gene-carrying member found in the cell nucleus and composed of a DNA molecule and proteins (chromatin). Prokaryote organisms contain only one chromosome (circular DNA), while eukaryotes contain numerous chromosomes that comprise a genome. Chromosomes are divided into functional units called genes, each of which contains the genetic code (instructions) for making a specific protein.

What is chronic ?

Long lasting and severe; the opposite of acute. Examples of chronic diseases include: chronic atopic dermatitis; chronic bronchitis; chronic cough; chronic rhinitis; chronic ulcerative colitis.

What is chytrid ?

A group of fungi not completely understood by science. Not visible to the eye, they are small, with a mycelium and central sporophore, looking like a miniature octopus. They reproduce by means of self-propelling spores.

What is cilium (plural, cilia) ?

A hair-like oscillating structure that is used for locomotion or for moving particles. It projects from a cell surface and is composed of nine outer double microtubules with two inner single microtubules, and it is anchored by a basal body. Single-cell organisms, such as protozoa, use them for locomotion. The human female fallopian tubes use cilia to transport the egg from the ovary to the uterus.

What is circadian rhythm ?

A biological process that oscillates with an approximate 24-hour periodicity, even if there are no external timing cues; an internal daily biological clock present in all eukaryotes.

What is circular dichroism (CD) ?

A spectroscopic method that measures the difference in absorbance of left- and right-handed circularly polarized light by a material as a function of the wavelength. Most biological molecules, including proteins and NUCLEIC ACIDS, are CHIRAL and show circular dichroism in their ultraviolet absorption bands, which can be used as an indication of SECONDARY STRUCTURE. Metal centers that are bound to such molecules, even if they have no inherent chirality, usually exhibit CD in absorption bands associated with LIGAND-based or ligand-metal CHARGETRANSFER TRANSITIONs. CD is frequently used in combination with absorption and MCD studies to assign electronic transitions.

What is cis ?

In inorganic nomenclature, cis is a structural prefix designating two groups occupying adjacent positions. (The term is not generally recommended for precise nomenclature purposes of complicated systems.)

What is cisplatin ?

cis-Diamminedichloroplatinum(II). An antitumor drug highly effective in the chemotherapy of many forms of cancer. Of major importance in the antitumor activity of this drug is its interaction with the NUCLEIC ACID bases of DNA.

What is cistron ?

A segment of DNA that codes for a single polypeptide domain; another name for a gene.

What is cladistics ?

A way to classify organisms by common ancestry, based on the branching of the evolutionary family tree. Organisms that share a common ancestor and have similar features are put into groups called clades. At each diverging line, there are two branching lines of descendants, and evolution plays a role in future changes in characteristics.

What is cladogenesis ?

The evolutionary splitting of lineages; one or more new species comes from an existing parent species, i.e., speciation. Also called branching evolution.

What is cladogram ?

A pictorial representation of a branching tree that depicts species divergence from a common ancestry.

What is class ?

The taxonomic ranking of plants and animals that is between phylum and order.

What is classical conditioning ?

The presentation of two stimuli at the same point in time: a neutral stimulus and a conditioned stimulus; the changes in behavior arising from the presentation of one stimulus in the presence of another. The pairing leads to the neutral stimulus associating with the properties of the conditioned.

What is cleavage ?

The process of cell division in an early embryo. Initial stages in embryonic development where the zygote converts to a ball of cells through divisions of clearly marked blastomeres, usually from a succession from first through sixth cleavages (2–64 cells). Each species of organism displays a characteristic cleavage pattern that can be observed. Cleavage divides the embryo without increasing its mass.

What is cleavage furrow ?

A groove composed of actin-rich contractile microfilaments that draws in tight to separate daughter cells during cytokinesis. Also called the contractile ring.

What is cleistogamous ?

A flower that does not open and is self-pollinated. Pollen is transferred directly from the anthers to the stigma of the same flower.

What is cleptoparasite ?

The parasitic relation in which a female seeks out the prey or stored food of another female, usually of another species, and appropriates it for the rearing of her own offspring.

What is climax ?

The final stage in succession where the constituent species populations fluctuate normally instead of acting as replacements of other species. The constituent species will self-perpetuate as long as all natural conditions are favorable and continue.

What is cline ?

The establishment of plant populations over a specific geographic range that have adapted to different locations and have become slightly different from one another. The plants show a gradient of change over the range, with the frequency of a particular gene either increasing or decreasing over the range. Under the right conditions, speciation may occur over time.

What is cloaca ?

An all-purpose opening that serves as a digestive, excretory, and reproductive tract for most vertebrates, with the exception of the majority of mammals.

What is clonal deletion ?

A mechanism whereby the loss of lymphocytes of a particular specificity is due to contact with either “self” or an artificially introduced antigen.

What is clonal selection theory (Burnett theory) ?

Clonal selection theory states that the specificity and diversity of an immune response are the result of selection by an antigen of specifically reactive clones from a large repertoire of preformed lymphocytes, each with individual specificities.

What is clone ?

A population of organisms, cells, viruses, or DNA molecules that is derived from the replication of a single genetic progenitor. In the case of B cells, each B cell has a typical Ig, and so all the cells that descend from one B cell (the clone) have the same Ig. Typically, a cancer is a clone of cells. Sometimes, clone is also used to refer to a number of recombinant DNA molecules all carrying the same inserted SEQUENCE.

What is cloning vector ?

Any organism or agent (virus, plasmid) that is used to introduce foreign DNA into host cells.

What is closed circulatory system ?

A type of circulatory system where the blood is contained within a system of vessels and the heart; blood vessels carry blood through all the organs.

What is cluster ?

A number of metal centers grouped closely together that can have direct metal-bonding interactions or interactions through a BRIDGING LIGAND, but are not necessarily held together by these interactions. Examples can be found under the entries [2FE-2S], [4FE-4S], FERREDOXIN, HIPIP, IRON-SULFUR CLUSTER, FEMO-COFACTOR, FERRITIN, METALLOTHIONEIN, NITROGENASE, and RIESKE IRON-SULFUR PROTEIN.

What is clusters of differentiation (CD) ?

Cluster of antigens, with which antibodies react, that characterize a cell surface marker.

Lymphocytes can be divided into subsets either by their functions or by surface markers. The availability of monoclonal Abs raised against lymphocytes has allowed for the demonstration of several lymphocyte subsets, which express a combination of certain atinocytes, and glial cells. HIV invades cells by attaching itself to the CD4 molecule (CD4 receptor). The number of T4 cells in a blood sample is used to measure the health of the immune system in people with HIV.

Helper T cell (CD4 cell, helper, helper cell, T helper cell, T helper lymphocyte, T4 cell) A subset of T cells that carry the T4 marker and are essential for turning on antibody production, activating cytotoxic T cells, and initiating other immune responses. The number of T4 cells in a blood sample is used to measure the health of the immune system in people with HIV. T helper lymphocytes contain two subsets, TH1 and TH2 cells.

CD8 cell (T suppressor cell, T8 cell)The existence of these cells is a relatively recent discovery, and hence their functioning is still somewhat debated. The basic concept of suppressor T cells is a cell type that specifically suppresses the action of other cells in the immune system, notably B cells and T cells, thereby preventing the establishment of an immune response. How this is done is not known with certainty, but it seems that certain specific antigens can stimulate the activation of the suppressor T cells. Discrete epitopes have been found that display suppressor activity on killer T cells, T helper cells, and B cells. This suppressor effect is thought to be mediated by some inhibitory factor secreted by suppressor T cells. It is not any of the known lymphokines. A fact that renders the study of this cell type difficult is the lack of a specific surface marker. Most suppressor T cells are CD8 positive, as are cytotoxic T cells.

What is clutch ?

The eggs laid in a nest by an individual bird.

What is cobalamin (vitamin B12) ?

A vitamin synthesized by microorganisms and conserved in animals in the liver. Deficiency of vitamin B12 leads to pernicious ANEMIA. Cobalamin is a substituted CORRIN-Co(III) complex in which the cobalt atom is bound to the four nitrogen atoms of the corrin ring, an axial group R and 5,6-dimethylbenzimidazole. The latter is linked to the cobalt by the N-3 nitrogen atom and is bound to the C-1 carbon of a ribose molecule by the N-1 nitrogen atom. Various forms of the vitamin are known with different R groups, such as R=CN, cyanocobalamin;
R=OH, hydroxocobalamin; R=CH3, methylcobalamin; R=adenosyl, COENZYME B12.

What is cochlea ?

The inner ear; a circular or coiled snaillike shell that contains a system of liquid-filled tubes with tiny hair cells. Sound signals pass from the cochlea via the oscillating hair cells, which transform them into electrical signals along the auditory nerve to the brain stem, where they activate other nerves in the brain.

What is cockroach ?

The order Blattodea that contains the insects also known as the “cucaracha,” black beetle, water bug, Yankee settler, shiner, and a host of other names; it is one of the most hated insects known to man. There are 4,000 species, but only about 12 are commonly associated with humans. Common species include: Blatella germanica, Blatta orientalis, Periplaneta americana, Periplaneta australasiae, Periplaneta brunnea, Periplaneta fuliginosa, and Supella longipalpa.

What is codominance ?

When both alleles in a heterozygote are expressed phenotypically.

What is codon ?

A sequence of three consecutive NUCLEOTIDES that occurs in mRNA and (a) directs the incorporation of a specific amino acid into a protein, or (b) represents the starting or termination signal of protein synthesis.

What is coefficient of kinship ?

The kinship coefficient expresses the chance of finding common genes on the same locus. It also expresses the probability that alleles drawn randomly from each of two individuals are identical by descent. It is also the relationship between a pair of individuals.

What is coefficient of variation ?

A measure of dispersion around the mean (average).

What is coelacanth ?

A 400-million-year-old “living fossil,” believed to have gone extinct 65 million years ago during the Cretaceous period and predating the dinosaurs by millions of years. The coelacanth was found alive in 1938 in South Africa. Today, Latimeria chalumnae and Latimeria menadoensis represent a once widespread family of sarcopterygian (fleshy-finned) coelacanth fishes. There are more than 120 species known from fossils. coelom A fluid-filled body cavity lined with mesoderm where organs can develop.

What is coelomate ?

Any organism whose body cavity is lined by mesoderm; animals possessing a coelom. These included the phylas: Entoprocta, Ectoprocta, Phoronida, Brachiopoda, Mollusca, Priapulida, Sipuncula, Echiura, Annelida, Tardigrada, Pentastoma, Onychophora, Arthropoda, Pogonophora, Echinodermata, Chaetognatha, Hemichordata, and Chordata.

What is coenocytic ?

Having multiple nuclei embedded in cytoplasm without cross walls; the nuclei lie in a common matrix. Also denotes a mycelium where the hyphae lack septa, i.e., members of the Oomycota and Chytridiomycota.

What is coenzyme ?

A low-molecular-weight, nonprotein organic compound (often a NUCLEOTIDE) participating in enzymatic reactions as a dissociable acceptor or donor of chemical groups or electrons.

What is coevolution ?

The evolution of two species where the evolutionary changes in one of the species influences the evolution of the other. A classic example is the long, narrow bill of the hummingbird. It has coevolved with tubular flowers, and the adaptation of its bill allows it to feed on plants with long, tubular flowers. These flowers in turn have adapted (coevolved) for fertilization by the hummingbirds when they take their nectar.

What is cofactor ?

An organic molecule or ion (usually a metal ion) that is required by an ENZYME for its activity. It may be attached either loosely (COENZYME) or tightly (PROSTHETIC GROUP).

What is cohesion ?

The force of attraction between molecules of the same substance that allows them to bind.

What is coitus ?

An alternative term for intercourse.

What is Coleoptera ?

The taxonomic order that comprises the insect group of beetles, one of the most adaptable and numerous insect groups. Beetles go through complete metamorphosis, have their hind wings covered by their fore wings, and are found in a variety of habitats.

What is collagen ?

The most abundant fibrous protein in the human body (about 30 percent) and in the animal kingdom; shapes the structure of tendons, bones, and connective tissues. There are several types (I, II, III, IV) that are found in bone, skin, tendons, cartilage, embryonic tissues, and basement membranes.

What is collecting duct ?

The area in the kidneys where urine is collected. Distal tubules of several nephrons join to form the collecting duct, which consists of the arcuate renal tubule, straight collecting tubule, and the papillary duct. Also known as the tubulus renalis colligens, or renal collecting tubule.

What is Collembola ?

An arthropod order resembling small insects that are wingless and can jump remarkable distances.

What is collenchyma cell ?

One of the three major plant cell types (dermal, ground, and vascular). Collenchyma cells are part of the ground tissue (ground tissues include parenchyma, collenchyma, and sclerenchyma cells) and are elongated and thick, with uneven cell walls and arranged in strands to provide support in areas of the plant that are growing.

What is colony-stimulating factor (CSF) ?

The category includes granulocyte-colony stimulating factor (GCSF), macrophage-colony stimulating factor (M-CSF), and granulocyte-macrophage-colony stimulating factor (GM-CSF). These are all cytokine proteins that stimulate growth and reproduction of certain kinds of blood cells in the bone marrow. Also referred to as growth factors. The production of white blood cells is controlled by colony-stimulating factors. Cancer chemotherapy and inherited disorders are among the causes of low white-cell counts, which lower resistance to infection. Thus, CSFs are being investigated not only as a way to counteract low white-cell counts but also as a way to produce specific types of white blood cells. In addition, there is hope that CSFs can stimulate the body to produce additional bone marrow as well as cause some cancer cells to stop dividing.

What is combinatorial library ?

A set of compounds prepared by combinatorial synthesis.

What is combinatorial synthesis ?

A process to prepare large sets of organic compounds by combining sets of building blocks.

What is commensalism ?

One of the forms of symbiosis. In this case, one organism benefits and the other is not affected.

What is community ?

All of the organisms, plant and animal, that inhabit a specific geographic area.

What is companion cell ?

A type of plant cell that is connected to a sieve-tube member, making up the phloem tissue. It retains the nucleus and dense cytoplasm to service adjacent sieve tube members, and it helps pump sugars into the phloem.

What is comparative molecular field analysis (CoMFA) ?

A three-dimensional quantitative structure-activity relationship (3D-QSAR) method that uses statistical correlation techniques for analysis of the quantitative relationship between (a) the biological activity of a set of compounds with a specified alignment and (b) their three-dimensional electronic and steric properties. Other properties such as hydrophobicity and hydrogen bonding can also be incorporated into the analysis.

What is competitive inhibitor ?

A substance that resembles the substrate for an enzyme, both in shape and size, and competes with the substrate for the substrate binding site on the enzyme, thereby reducing the rate of reaction by reducing the number of enzyme molecules that successfully bind.

What is complementary DNA (cDNA) ?

A laboratoryproduced DNA section that is created by extracting a single-stranded RNA from an organism as a templateand transcribing it back into a double-stranded DNA using the enzyme reverse transcriptase. However, the cDNA does not include introns, those portions of the DNA that were spliced out while still in the cell. Used for research purposes and can be cloned into plasmids for storage.

What is complement fixation ?

The consumption of complement, a complex of nine blood serum proteins that interact sequentially with specific antibodies (and concentrates in inflamed regions), by an antibody-antigen reaction containing complement-fixing antibodies. Used as a test to detect antibodies that react against a particular antigen such as a virus.

What is complement system ?

A set of 30 glycoproteins in the blood serum in the form of components, factors, or other regulators that work at the surface of cells as receptors. Inactive until activated by immune responses, the system acts to dissolve and remove immune complexes and kill foreign cells.

What is complete digestive tract (alimentary canal) ?

A tube that has an opening and end (mouth and anus) that is used in digestion. The complete digestive tract is one where food is ingested at one end of the tract, the mouth, and wastes from digestion are passed out of the tract at the other end, the anus. An incomplete digestive tract has just one opening used both to take in food and to eliminate wastes.

What is complete flower ?

Any flower that has all four major parts: SEPALS, PETALS, STAMENS, and CARPELS.

What is Compositae (Asteraceae) ?

The composites (also known as the daisy or sunflower family), Compositae or Asteraceae, are one of the largest plant families, containing almost 20,000 species. Most of these species are herbs, but there are also some shrubs, trees, and vines. The family includes many edible salad plants (e.g., lettuce, endive, chicory, and artichoke); cultivated species such as the marigolds, daisies, sun flowers, and chrysanthemums; as well as many common weeds and wildflowers. It is primarily the latter, for example, ragweed and mugwort, that are involved in pollen-induced seasonal allergies. Ragweed (Ambrosia)
Ragweed refers to the group of approximately 15 species of weed plants, belonging to the Compositae family. Most ragweed species are native to North America, although they are also found in Eastern Europe and the French Rhône Valley. The ragweeds are annuals characterized by their rough, hairy stems and mostly lobed or divided leaves. The ragweed flowers are greenish and inconspicuously concealed in small heads on the leaves. The ragweed species, whose copious pollen is the main cause of seasonal allergic rhinitis (hay fever) in eastern and middle North America, are the common ragweed (A. artemisiifolia) and the great, or giant, ragweed (A. trifida). The common ragweed grows to about 1 meter (3.5 feet); is common all across North America; and is also commonly referred to as Roman wormwood, hogweed, hogbrake or bitterweed. The giant ragweed, meanwhile, can reach anywhere up to 5 meters (17 feet) in height and is native from Quebec to British Columbia in Canada and southward to Florida, Arkansas, and California in the United States. Due to the fact that ragweeds are annuals, they can be eradicated simply by mowing them before they releasetheir pollen in late summer. Mugwort (Artemisia vulgaris, A. campestris, A. dracunculus, A. rupestris, A. mutellina, A. absinthium, A. maritima, A. austriaca, A. pontica, A. laciniata, A. abrotanum, A. annua, A. tilessii)A shrubby weed most commonly found on wasteland, mugwort can reach heights of up to 2 meters (7 feet) and is characterized by quite small, yellow to reddish brown flowers and a woody stem. The mugwort pollen season (in central Europe) is generally late July to September, with a peak around mid-August. Mugwort is known to crossreact with almost all members of the Compositae family, especially the ragweeds, as well as dandelions, sunflowers, chamomille, and all daisylike flowers. Mugwort also displays an important cross-reaction in the context of food allergies to celery.

What is compound ?

The combination of two or more different elements, held together by chemical bonds. The elements in a given compound are always combined in the same proportion by mass (law of definite proportion).

What is compound eye ?

A multifaceted eye found in most invertebrates. The eye is composed of many separate cylinder-shaped (hexagonal) units called ommatidia. Each ommatidium has its own surface area, lens (crystalline cone), light receptors (retinulae), and optic nerve fiber. The images from the collection of ommatidia are then processed.

What is comproportionation ?

Describes a chemical reaction when a mixture of species in different oxidation states reacts to produce a product that is in a different but more stable intermediate oxidation state. A type of redox reaction. For example, when iodide ions and iodate ions react together, they form elemental iodine. The reverse of DISPROPORTIONATION.

What is computational chemistry ?

A discipline using mathematical methods for the calculation of molecular properties or for the simulation of molecular behavior.

What is computer-assisted drug design (CADD) ?

Involves all computer-assisted techniques used to discover, design, and optimize biologically active compounds with a putative use as DRUGs.

What is concanavalin A ?

A protein from jack beans, containing calcium and manganese, that agglutinates red blood cells and stimulates T lymphocytes to undergo mitosis.

What is condensation reaction (dehydration reaction) ?

A (usually stepwise) reaction in which two or more reactants (or remote reactive sites within the same molecular entity) yield a single main product with accompanying formation of water or of some other small molecule, e.g., ammonia, ethanol, acetic acid, hydrogen sulfide.

The mechanism of many condensation reactions has been shown to comprise consecutive addition and elimination reactions, as in the base-catalyzed formation of (E)-but-2-enal (crotonaldehyde) from acetaldehyde via 3-hydroxybutanal (aldol). The overall reaction in this example is known as the aldol condensation.

The term is sometimes also applied to cases where the formation of water or another simple molecule does not occur.

What is cone cell ?

A photoreceptor cell of the eye that is found in the retina and densely populates the central portion, called the macula. It is responsible for seeing color and fine visual detail.

What is confidence limits ?

A statistical parameter defining the lower and upper boundaries/values of a confidence interval. A range of values that is estimated from a sample group that is highly likely to include the true, although unknown, value.

What is configuration ?

In the context of stereochemistry, the term is restricted to the arrangement of atoms of a molecular entity in space that distinguishes the entity as a STEREOISOMER, the isomerism of which is not due to CONFORMATION differences.

What is conformation ?

A spatial three-dimensional arrangement of atoms in a molecule that can rotate without breaking any bonds.

What is congener ?

A substance—literally con- (with) generated—synthesized by essentially the same synthetic chemical reactions and the same procedures. An ANALOG is a substance that is analogous in some respect to the prototype agent in chemical structure.

The term congener, while most often a synonym for homologue, has become somewhat more diffuse in meaning, so that the terms congener and analog are frequently used interchangeably in the literature.

What is conidium ?

A nonmotile asexual spore borne at the tip of a special hyphal branch called a conidiophore. It is diverse in form: single or multicelled; simple or complex; round, elongated, or spiral shaped. It is found in ascomycetes and basidiomycetes only.

What is conifer ?

A seed-bearing evergreen tree or shrub, a gymnosperm, that reproduces by the use of cones. Conifers inhabit cool temperate regions and have leaves in the form of needles or scales. Examples include pines, fir, spruce, and hemlock. The gymnosperms are the plant order of nonflowering plants, which are characterized by the fact that their seeds are exposed to the air during all stages of development. The name gymnosperm means “naked seeds.” Gymnosperms are woody plants and are pollinated by wind, hence their potential for inducing seasonal allergy. The seed-bearing structure is typically a cone. Gymnosperm members include the cycads (e.g., sago palm); ginkgoes; conifers (order Pinales) (e.g., monkey-puzzle, nutmeg); family Cupressaceae (e.g., cedar); family Taxaceae (e.g., yew); family Taxodiaceae (e.g., redwood); and family Pinaceae (e.g., pine).

What is conjugation ?

The process of transferring genetic material between two organisms that are temporarily joined.

What is consensus sequence ?

A SEQUENCE of DNA, RNA, protein, or carbohydrate—derived from a number of similar molecules—that comprises the essential features for a particular function.

What is conservation biology ?

A branch of biology concerned with the loss of world biodiversity.

What is conspecific ?

Refers to animals (individuals or populations) of the same species.

What is continental drift ?

Two hundred million years ago the Earth’s continents were joined together to form one gigantic supercontinent called Pangaea. As the rock plates that the continents sit on moved, the supercontinent broke up and began to move apart. This process is known as continental drift.

What is connective tissue (myofascial matrix; fascia) ?

A very strong tissue that is the main support system for the body, an important component of muscles, tendons, ligaments, cartilage, and bones. It wraps around various systems as a tough fibrous sheath, giving shape and strength. Composed of cells and extracellular matrix.

What is contraception ?

The conscious and deliberate act of preventing pregnancy.

What is contrast agent ?

Paramagnetic (or FERROMAGNETIC) metal complex or particle causing a decrease in the relaxation times (increase in relaxivity) of nuclei detected in an image, usually made of water.

What is convection ?

Fluid or air circulation driven by temperature gradients; the rising of warm air and the sinking of cool air. The transfer of heat by circulation or movement of heated liquid or gas.

What is convergent evolution ?

When two unrelated species share similar traits arising from each species independently adapting to a similar environmental condition.

What is cooperativity ?

The phenomenon that binding of an effector molecule to a biological system either enhances or diminishes the binding of a successive molecule, of the same or different kind, to the same system. The system may be an ENZYME or a protein that specifically binds another molecule such as oxygen or DNA. The effector molecule may be an enzyme SUBSTRATE or an ALLOSTERIC EFFECTOR. The enzyme or protein exists in different CONFORMATIONs, with different catalytic rates or binding affinities, and binding of the effector molecule changes the proportion of these conformations. Enhanced binding is named positive cooperativity; diminished binding is named negative cooperativity. A well-known example of positive cooperativity is in HEMOGLOBIN. In biocatalysis it was originally proposed that only multiSUBUNIT enzymes could respond in this way. However, single-subunit enzymes may give such a response (so-called mnemonic enzymes).

What is coordination ?

A coordination entity is composed of a CENTRAL ATOM, usually that of a metal, to which is attached a surrounding array of other atoms or group of atoms, each of which is called a LIGAND. A coordination entity can be a neutral molecule, a cation, or an anion. The ligands can be viewed as neutral or ionic entities that are bonded to an appropriately charged central atom. It is standard practice to think of the ligand atoms that are directly attached to the central atom as defining a coordination polyhedron (tetrahedron, square plane, octahedron, etc.) about the central atom. The coordination number is defined as being equal to the number of sigma-bonds between ligands and the central atom. This definition is not necessarily appropriate in all areas of (coordination) chemistry. In a coordination formula, the central atom is listed first. The formally anionic ligands appear next, and they are listed in alphabetic order according to the first symbols of their formulas. The neutral ligands follow, also in alphabetic order, according to the same principle. The formula for the entire coordination entity, whether charged or not, is enclosed in square brackets. In a coordination name, the ligands are listed in alphabetic order, without regard to charge, before the name of the central atom. Numerical prefixes indicating the number of ligands are not considered in determining that order. All anionic coordination entities take the ending -ate, whereas no distinguishing termination is used for cationic or neutral coordination entities.

What is cordilleran ?

A system of parallel mountain ranges forming the spine of continents (e.g., Andes in South America, Rocky Mountains in North America). Spanish for mountain range.

Who was Cori, Carl Ferdinand ?

Cori, Carl Ferdinand (1896–1984) was Austrian Biochemist Carl Ferdinand Cori was born in Prague on December 5, 1896, to Carl I. Cori, director of the Marine Biological Station in Trieste. He studied at the gymnasium in Trieste and graduated in 1914, when he entered the German University of Prague to study medicine. During World War I, he served as a lieutenant in the sanitary corps of the Austrian army on the Italian front; he returned to the university to graduate as a doctor of medicine in 1920. He spent a year at

the University of Vienna and a year as assistant in pharmacology at the University of Graz until, in 1922, he accepted a position as biochemist at the State Institute for the Study of Malignant Diseases in Buffalo, New York. In 1931, he was appointed professor of pharmacology at the Washington University Medical School in St. Louis, where he later became professor of biochemistry.

He married Gerty Theresa CORI (née Radnitz) in 1920. They worked together in Buffalo. When he moved to St. Louis, she joined him as a research associate. Gerty Cori was made professor of biochemistry in 1947.

Jointly, they researched the biochemical pathway by which glycogen, the storage form of sugar in liver and muscle, is broken down into glucose. They also determined the molecular defects underlying a number of genetically determined glycogen-storage diseases. For these discoveries the Coris received the 1947 Nobel Prize in physiology or medicine.

They became naturalized Americans in 1928. He died on October 20, 1984, in Cambridge, Massachusetts. His wife died earlier, in 1957.

What is Cori, Gerty Theresa (née Radnitz) ?

Cori, Gerty Theresa (née Radnitz) (1896–1957) was Austrian Biochemist Gerty Theresa Cori (née Radnitz) was born in Prague on August 15, 1896, and received her primary education at home before entering a lyceum for girls in 1906. She entered the medical school of the German University of Prague and received the doctorate in medicine in 1920. She then spent two years at the Carolinian Children’s Hospital before emigrating to America with her husband, Carl, whom she married in 1920. They worked together in Buffalo, and when he moved to St. Louis, she joined him as a research associate. She was made professor of biochemistry in 1947.

Jointly, they researched the biochemical pathway by which glycogen, the storage form of sugar in liver and muscle, is broken down into glucose. They also determined the molecular defects underlying a number of genetically determined glycogen-storage diseases. For these discoveries the Coris received the 1947 Nobel Prize for physiology or medicine. She died on October 26, 1957.

What is cork cambium ?

A narrow cylindrical sheath of plant tissue (meristematic) that produces cork cells that replace the epidermis during secondary growth. The resulting cork is impregnated with suberin, a waterproof, waxy fatty acid derivative.

What is corphin ?

The F-430 cofactor found in methyl-coenzyme M reductase, a nickel-containing ENZYME that catalyzes one step in the conversion of CO2 to methane in methanogenic bacteria. The Ni ion in F-430 is coordinated by the tetrahydrocorphin LIGAND. This ligand combines the structural elements of both PORPHYRINs and CORRINs.

What is corpus luteum ?

A secreting tissue in the ovary, formed from a collapsed follicle, that produces increasing levels of estrogen as well as progesterone after ovulation. These hormones prepare the endometrium for the implantation of a fertilized egg. However, if pregnancy does not occur, the corpus luteum regresses and these hormone levels decline. This results in the breakdown of the endometrium and initiates menstrual bleeding. If pregnancy does occur, the corpus luteum begins to produce human chorionic gonadotropin (HCG).

What is corrin ?

A ring-contracted PORPHYRIN derivative that is missing a carbon from one of the mesopositions (C-20). It constitutes the skeleton C19H22N4 upon which various B12 vitamins, COFACTORs, and derivatives are based.

What is cortex ?

Generic term for the outer layer of an organ. Also the region of parenchyma cells in the root between the stele and epidermis filled with ground tissue.

What is coterie ?

The basic society of prairie dogs, or a small, close group.

What is cotransport ?

A simultaneous transporting of two solutes across a membrane by a transporter going one way (symport) or in opposite directions (antiport).

What is cotyledons ?

Leaflike structures (seed leaves) produced by the embryo of flowering plants, the dicots (Magnoliopsida), and the monocots (Liliopsida). They serve to absorb nutrients in the seed until the seedling is able to produce true leaves and begin photosynthesis. In monocots, the embryo has a single cotyledon, while in dicots, the embryo has two cotyledons.

What is countercurrent exchange ?

The effect caused when two fluids move past each other in opposite directions and facilitate the efficient exchange of heat, gas, or substance. For example: the passage of heat from one blood vessel to another; rete mirabile, the countercurrent exchange structure of capillaries that allows gas uptake in a fish swim bladder; the kidney nephron loop, a tubular section of nephron between the proximal and distal convoluted tubules where water is conserved and urine concentrates by a countercurrent exchange system; and the upper airway where, upon expiration, heat and moisture are retained and given up to relatively cool and dry inspired gases.

Who was Cournand, André-Frédéric ?

Cournand, André-Frédéric (1895–1988) was French Physiologist André-Frédéric Cournand was born in Paris on September 24, 1895, to Jules Cournand, a stomatologist, and his wife Marguérite Weber. He received his early education at the Lycée Condorcet, received a bachelor’s degree at the Faculté des Lettres of the Sorbonne in 1913, and received a diploma of physics, chemistry, and biology of the Faculté des Sciences the following year.

He began medical studies in 1914, but served in the French Army from 1915 to 1918, returning to medical studies at the Interne des Hôpitaux de Paris in 1925. He received an M.D. from the Faculté de Médecine de Paris in May 1930 and secured a residency in the Tuberculosis (later Chest) Service of the Columbia University Division at Bellevue Hospital, New York. He became chief resident of this service and conducted research on the physiology and physiopathology of respiration under the guidance of Dickinson W. RICHARDS. He became an American citizen in 1941 and retired from Columbia in 1964.

Together, Cournand and Richards collaborated in clinical lung and heart research. They perfected a pro cedure introduced by Werner Forssmann and called Forssmann’s procedure, now called cardiac catheterization (a tube is passed into the heart from a vein at the elbow). This made it possible to study the functioning of the diseased human heart and to make more accurate diagnoses of the underlying anatomic defects. They also used the catheter to examine the pulmonary artery, improving the diagnosis of lung diseases as well. He shared the Nobel Prize in physiology or medicine with Dickinson W. Richards and Werner FORSSMANN for their discoveries concerning heart catheterization and circulatory changes in 1956.

Cournand served on the editorial boards of many medical and physiological publications, including Circulation, Physiological Reviews, The American Journal of Physiology, and also Journal de Physiologie and Revue Française d’Etúdes Cliniques et Biologiques. He was a member of numerous scientific organizations and received awards for his work. He died on February 19, 1988, at Great Barrington, Massachusetts.

What is court (lek) ?

The area defended by individual males within an area where birds gather for display and courtship.

What is covalent bond ?

A region of relatively high electron density between nuclei that arises at least partly from sharing of electrons and gives rise to an attractive force and characteristic internuclear distance.

What is covalent bond ?

A region of relatively high electron density between nuclei that arises at least partly from sharing of electrons and gives rise to an attractive force and characteristic internuclear distance.

What is crista ?

The inner membrane of mitochondrion, where respiration takes place; location of the electron transport chain and enzymes that catalyze ATP synthesis. Also the term applied to sensory cells within an ear’s semicircular canal that detect fluid movement. Also means crest, such as the crista galli, the comb on a rooster.

Who was Croll, James ?

Croll, James (1821–1890) British Carpenter, Physicist James Croll was born in Cargill, Perthshire, Scotland, on January 2, 1821. He was the son of David Croll, a stonemason from Little Whitefield, Perthshire, and Janet Ellis of Elgrin. He received an elementary school education until he was 13 years old. His knowledge of science was the result of vigilance, since he was self-taught. On September 11, 1848, he married Isabella MacDonald, daughter of John MacDonald.

Croll started his career as a carpenter apprenticed to a wheelwright when he was young; then he became a joiner at Banchory and opened a shop in Elgin. In 1852, he opened a temperance hotel in Blairgowrie, and later, in 1853, became an insurance agent for the Safety Light Assurance Company ending up in Leicester.

His first book, The Philosophy of Theism, was published in 1857 and based on the influence of the metaphysics of Jonathan Edward. However due to an injury, he ended up obtaining a job as a janitor at Anderson’s College and Museum in Glasgow in 1859. Being a janitor gave him enough free time after his daily chores to utilize the museum’s extensive library. There, he would spend the night reading books on physics, including the works of Joseph A. Adhémar, the French mathematician, who noted in 1842 that the Earth’s orbit is elliptical rather than spherical. Adhémar proposed in his book Revolutions de la Mer, Deluges Periodics (Revolutions of the sea, periodic floods) that the precession of the equinoxes produced variations in the amount of solar radiation striking the planet’s two hemispheres during the winter time (insolation), and this, along with gravity effects from the sun and moon on the ice caps, is what produced ice ages alternately in each hemisphere during a 26,000year cycle. Precession is the slow gyration of Earth’s axis around the pole of the ecliptic, caused mainly by the gravitational pull of the sun, moon, and other planets on Earth’s equatorial bulge. Croll also read about the new calculations of the Earth’s orbit by French astronomer Urbain Jean Joseph Leverrier (a discoverer of the planet Neptune).

Croll decided to work on the origins of the ice ages, since he did not agree with the prevailing attitude that they were leftover relics from the biblical Great Flood, and additionally he found errors in Adhémar’s work. Croll came to the conclusion that the overriding force changing climate and creating the ice ages on Earth was due to variations in insolation, which is the rate of delivery of solar radiation per unit of horizontal surface, i.e., the sunlight hitting the Earth.

Croll first realized that Adhémar did not take into account the shape of the Earth’s orbit that varied over time and its effect on precession, so he calculated the eccentricity over several million years. This eccentricity (the distance between the center of an eccentric and its axis), in this case the degree of Earth’s elliptic orbit, he proposed, varied on a time scale of about 100,000 years. Since variations in eccentricity only produced small changes in the annual radiation budget of Earth, and not enough to force an ice age, Croll developed the idea of climatic feedbacks, such as changes in surface albedo (reflection). He predicted that the last ice age was over about 80,000 years ago.

During the 1860s, he published his theories in a number of papers: “On the Physical Cause of Changes of Climate during Geological Epochs” (1864); “The Eccentricity of the Earth’s Orbit” (1866, 1867); “Geological Time and Date of Glacial and Miocene Periods” (1868); “The Physical Cause of the Motion of Glaciers” (1869, 1870); “The Supposed Greater Loss of Heat by the Southern Hemisphere” (1869); “Evolution by Force Impossible: A New Argument against Materialism” (1877). During this time he was the keeper of maps and correspondence at the Scottish Geological Survey starting in 1867, where he mingled with some of the best geologists of the time until he retired in 1880.

In 1875 he published Climate & Time in Their Geological Relations, where he summed up his research on the ancient condition of the Earth. On January 6, 1876, he was elected a fellow of the Royal Society of London. Charles Darwin was among the many supporters of his nomination. He received an LL.D. (law degree) that year from St. Andrews College. While his main interests were in the field of paleoclimate change, he also put forth theories about ocean currents and their effects on climate during modern times.

However, some of his thoughts and ideas were wrong. For example, Croll believed that ice ages varied in the hemispheres, and his estimated age for the last ice advance ending 80,000 to 100,000 years ago was wrong. It ended between 14,000 and 10,000 years ago, as research currently shows. Because of these errors, Croll fell out of vogue until 1912, when Yugoslav geologist Milutin Milankovitch revised Croll’s theories in his book, Canon of Insolation.

Croll published close to 90 papers on a variety of subjects, such as “Ocean Currents” (1870, 1871, 1874); “Change of Obliquity of Ecliptic: Its Effect on Climate” (1867); “Physical Cause of Submergence during Glacial Epoch” (1866, 1874); “Boulder Clay of Caithness & Glaciation of North Sea” (1870); “Method of Determining Mean Thickness of Sedimentary Rocks” (1871); and “What Determines Molecular Motion? The Fundamental Problem of Nature” (1872).

A famous debate on the nature of deep-sea circulation between Croll and Irish scientist William Carpenter during the 1860s to 1880s was well discussed in the literature and around scientific circles via correspondence. In 1885, he published Climate and Cosmology to answer critics of his earlier work Climate & Time in Their Geological Relation. Five years later, plagued by ill health his whole life, he died in Perth on December 15, at age 69, shortly after publishing a small book called The Philosophical Basis of Evolution.

What is Cro-Magnon ?

An early group of Homo sapiens (humans) that lived in Europe around 40,000 years ago.

What is crossing over ?

A process during meiosis when alleles on homologous chromosomes (chromosomes that pair with each other at meiosis) switch places, increasing the possible combinations of alleles and thus increasing the variability of the whole genome. Also called recombination.

What is cross-pollination ?

When pollen from the anther of a flower of one plant is transferred to the flowers (stigma) of a different plant.

What is cross-reactivity ?

The ability of an immunoglobulin, specific for one antigen, to react with a second antigen. A measure of relatedness between two different antigenic substances.

What is Crustacea ?

All crustaceans have two pairs of antennae, a pair of mandibles, a pair of compound eyes (usually on stalks), two pair of maxillae on their heads, and a pair of appendages on each body segment (head, thorax, and abdomen). There are about 30,000 species of this subphylum within five classes (Remipedia, Cephalocarida, Branchiopoda, Maxillopoda, and Malacostraca). Includes lobsters, crabs, crayfish, shrimp, copepods, isopods, barnacles, and others. Many of them are important economic species for human consumption.

What is cryptic ?

Describes the ability to conceal or camouflage.

What is cryptic coloration ?

A camouflage technique whereby an organism matches its background, concealing itself from predators or prey, e.g., the peppered moth.

What is crystal field ?

Crystal field theory is the theory that interprets the properties of COORDINATION entities on the basis that the interaction of the LIGANDs and the CENTRAL ATOM is a strictly ionic or ion-dipole interaction resulting from electrostatic attractions between the central atom and the ligands. The ligands are regarded as point negative (or partially negative) charges surrounding a central atom; covalent bonding is completely neglected. The splitting or separation of energy levels of the five degenerate d-orbitals in a transition metal, when the metal is surrounded by ligands arranged in a particular geometry with respect to the metal center, is called the crystal field splitting.

What is cuticle ?

A protective impermeable waxy substance formed from the polymer cutan that covers the outside of leaves, stems, and fruits and forms the protective layer of arthropods.

What is cyanobacteria ?

Bacteria, formerly known as bluegreen algae; aquatic and photosynthetic organisms that live in water and manufacture their own food. Their fossils go back more than 3.5 billion years, making them the oldest known species, and they are the contributors to the origin of plants.

What is cybernetics ?

The science that studies the methods to control behavior and communication in animals (and machines).

What is cyclic AMP (cAMP; 3’,5’-AMP) ?

Cyclic adenosine monophosphate. A compound synthesized from ATP (by the enzyme adenylyl cyclase) in living cells that acts as an intercellular and extracellular second messenger mediating peptide and amine hormones.

What is cyclic electron flow ?

Two photosystems are present in the thylakoid membrane of chloroplasts: photosystem I and photosystem II. The two photosystems work together during the light reactions of photosynthesis. The light-induced flow of electrons beginning with and returning to photosystem I to produce ATP without production of NADPH (nicotine adenine dinucleotide phosphate with hydrogen ) is cyclic electron flow. The generation of ATP by this process is called noncyclic photophosphorylation.

What is cyclin ?

A protein found in dividing cells that activates protein kinases (cyclin-dependent protein kinases), a type of enzyme that adds or removes a phosphate group from a target protein and controls the progression of one phase of the cell cycle to the next. The concentration of the cyclin increases and decreases during the cell cycle.

What is cyclin-dependent kinase ?

A protein kinase, an enzyme involved in regulating cell growth and division, that must be attached to cyclin to become activated.

What is cytochrome ?

A HEME protein that transfers electrons and exhibits intense absorption bands (the α and β bands, the α band having the longer wavelength) between 510 and 615 nm in the reduced form. Cytochromes are designated types a, b, c, or d, depending on the position of the α band, which depends on the type of heme. The iron undergoes oxidation–reduction between oxidation states Fe(II) and Fe(III). Most cytochromes are hemochromes, in which the fifth and sixth COORDINATION sites in the iron are occupied by strong field LIGANDs, regardless of the oxidation state of iron. Cytochromes can be distinguished by the wavelength of the α band, such as cytochrome c-550. Certain specific cytochromes with particular functions are designated with suffixes, such as cytochrome a1, b2, etc.

What is cytochrome-c oxidase ?

An ENZYME, ferrocytochrome-c: dioxygen OXIDOREDUCTASE, CYTOCHROME aa3. The major respiratory protein of animal and plant MITOCHONDRIA, it catalyzes the oxidation of Fe(II)cytochrome c, and the reduction of dioxygen to water. Contains two HEMEs and three copper atoms, arranged in three centers. Heme a3 and copper-B form a center that reacts with dioxygen; the second heme is cytochrome a; the third site, copper-A, is a dinuclear center.

What is cytochrome P-450 ?

General term for a group of HEME-containing MONOOXYGENASEs. Named from the prominent absorption band of the Fe(II)-carbonyl complex. The heme comprises PROTOPORPHYRIN IX, and the proximal LIGAND to iron is a cysteine sulfur. Cytochromes P-450 of microsomes in tissues such as liver are responsible for METABOLISM of many XENOBIOTICs, including drugs. Others, such as the mitochondrial ENZYMEs from adrenal glands, are involved in biosynthetic pathways such as those of steroids. The reaction with dioxygen appears to involve higher oxidation states of iron, such as Fe(IV)=O.

What is cytokines ?

Cytokines are soluble glycoproteins released by cells of the immune system (secreted primarily from leukocytes) that act nonenzymatically through specific receptors to regulate immune responses. Cytokines resemble hormones in that they act at low concentrations bound with high affinity to a specific receptor.

What is cytokinesis ?

The final stage of mitosis, when the parent cell divides equally by cell-wall formation into two daughter cells by way of a constriction and drawing in of an actin/myosin ring around the center of the cell.

What is cytoplasm ?

The part of protoplasm in a cell outside of and surrounding the nucleus. The contents of a cell other than the nucleus. Cytoplasm consists of a fluid containing numerous structures, known as organelles, that carry out essential cell functions.

What is cytoplasmic determinants ?

Substances distributed in an embryo, but present in an unfertilized egg, that appear in different blastomeres at the initial cleavage stage and influence their development fate.

What is cytoplasmic streaming ?

The movement and flow of cytoplasm, the living part of a cell outside the nuclear membrane. The primary method of movement of mate rials within cells, e.g., chloroplasts moving up to the surface of the leaf and then down, which appear to help in photosynthesis.

What is cytoskeleton ?

The internal support system and framework of a cell, comprising numerous microfilaments and tubules that branch throughout the cell. The cytoskeleton serves not only as mechanical support but also in transport functions.

What is cytosol ?

The semifluid portion of the cytoplasm, not including organelles.

What is cytoxic T cells (T killer cells) ?

Cells that kill target cells bearing appropriate antigen within the groove of an MHC (major histocompatibility complex) class I molecule that is identical to that of the T cell.