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Home >> Dictionary of Bioinformatics, Biochemistry, Biotechnology >> Capture Probe - Carcinoembryonic Antigen Cea
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Capsule An envelope of carbohydrate or slime layer that surrounds certain microorganisms and enables evasion of phagocytosis.
Capture PCR A PCR strategy in which linkers added to the ends of linear DNA molecules are used as primer biding sites and intramolecular stem-loop structures are exploited for strand specific priming. The products generated by amplification of the sequence between the two primers correspond can be captured by streptavidin.
Capture probe A phage or antibody probe that binds proteins in a sample enabling relative expression levels to be detected.
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Carbamoyl phosphate synthase I The rate-limiting enzyme of the urea cycle that requires N-acetylglutamate as an Allosteric activator two molecules of ATP Ammonia formed by the deamination of amino acids combines with carbon dioxide to form carbamoylphosphate.
Carbamoyl phosphate synthetase II A Cytosolic enzyme that catalyses the formation of carbamoyl phosphate from CO2, glutamine and ATP, the first step in pyrimidine biosynthesis.
Carbanion A negatively charged carbon atom.
Carbocation A positively charged carbon atom. Also termed carbonium ion.
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Carbohydrate Polyhdroxy aldehydes or ketones. An organic compound with the general formula Cn(H2O)n that performs many vital roles in living organisms. The simplest carbohydrates are the sugars (saccharides), such as glucose and sucrose. Polysaccharides are carbohydrates of higher molecular weight and complexity. These include starch an energy store in plant seeds and tubers; cellulose and lignin that form the cell walls and woody tissue of plants; and glycogen, the energy storage form in animals.
Carbohydrate antigen (CA) markers High-molecular weight mucins or blood group specific antigens found on tumour cell surface or secreted by the tumour cells. These have higher specificity than enzymes and hormones. Many CA markers are not specific to any particular tumour or tissue type with the exception of CA 125, which is specific for ovarian cancer. CA 19-9 is useful in monitoring response to treatment in adenocarcinoma of the pancreas, colorectal and gastric cancer, CA50 for colorectal carcinoma and CA 15-3 for carcinoma of the breast.
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Carbohydrate antigen (CA) markers CA 125 is a high molecular weight glycoprotein expressed by epithelial ovarian tumours as well as in normal and pathological tissues of mullerian duct origin. It is a useful marker for ovarian and endometrial carcinomas. CA 125 is useful in differentiating benign from malignant ovarian masses, detecting residual disease following cancer therapy and recurrent metastasis. CA 15-3, CA459 and CA27.29 serve as markers for carcinoma of the breast.
Carbon assimilation reactions Reaction sequences in which atmospheric carbon dioxide is converted into organic compounds.
Carbon dioxide cycle The flow of CO2 from organisms capable of photosynthesis (plants and algae) and conversion of CO2 to organic foodstuffs to all other organisms that consume the organic molecules and release CO2 as a waster product.
Carbon fixation The process by which photosynthesisers (plants and algae) convert inorganic carbon dioxide into organic molecules, chiefly carbohydrates used as food by other organisms.
Carbon fixation cycle See Calvin cycle.
Carbon fixation reaction The reaction catalysed by rubisco (during photosynthesis) or by other carboxylases, in which CO2 is incorporated into an organic compound.
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Carbon source An organic carbon-containing molecule that can be metabolized to produce energy in the form of ATP. Although carbohydrates function as carbon sources for most organisms, fats and some amino acids can also be used for energy production.
Carbonate dehydratase (CD; carbonic anhydrase) An enzyme that catalyses the reaction of carbon dioxide with water to form carbonic acid (H2CO3) which then dissociates to form hydrogen ion (H+) and bicarbonate ion (HCO3). The enzyme is present in high concentrations in the erythrocytes.
Carbonyl group A pair of atoms containing a carbon atom attached to an oxygen atom by a double bond (C=O).
Carboplatin A positively charged platinum complex that forms interstrand crosslinks with DNA. It is used in combination with other anticancer agents.
Carbowax See polyethylene glycol.
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Carboxyhaemoglobin (COHb) The product of carbon monoxide binding to haemoglobin. The affinity of haemoglobin for carbon monoxide is 200 times greater than for oxygen. COHb displaces oxygen from Oxyhaemoglobin and consciousness is lost when about half the Oxyhaemoglobin has been replaced by COHb.
Exposure to carbon monoxide occurs from car exhaust gas, coal gas and smoke from fires ad incomplete combustion of coal and tobacco smoke. Height amounts of COHb may be found in the blood of tobacco smokers. Carboxyhaemoglobin is cherry red in colour and can be quantitatively assayed by differential spectrophotometry owing to its differential absorption spectrum from haemoglobin.
Carboxyl (-COOH) group Carbon atom linked to an oxygen atom by a double bonds as well as to a hydroxyl group. Molecules that contain a carboxyl group are weak acids.
Carboxyl terminal residue The amino acid residue in a polypeptide chain with a free α-carboxyl group. It defines the carboxyl terminus of the polypeptide.
Carboxyl terminus The-COOH end of a peptide chain that is by convention written at the right end of a protein sequence.
Carboxylation Introduction of a carboxyl group (-COOH) or carbon dioxide into a compound.
Carboxylic acid A molecule containing a carbon atom that is attached to a hydroxyl group and to an oxygen atom by a double bond.
Carboxypeptidases Two enzymes (A and B) present in pancreatic juice. They catalyse the removal of the C-terminal amino acid from a peptide. While carboxypeptidase A removes any amino aid, carboxypeptidase B cleaves only lysine or arginine residues. These enzymes are used during peptide sequencing.
Carcinoembryonic antigen (CEA) A glycoprotein present in the gastrointestinal tract, liver and pancreas of the foetus between 2-6 months of intrauterine life. It is found in low concentrations in the plasma of normal adults. CEA is a marker for colorectal cancer especially in advanced stages. However, CEA lacks specificity and sensitivity.
High plasma concentrations are also seen in nonmalignant conditions such as liver disease, pulmonary emphysema, pancreatitis, inflammatory bowel disease, rectal polyps, being breast diseases and in heavy smokers. Furthermore, plasma CEA level does not correlate well with tumour burden and is therefore not useful in monitoring response to therapy. Plasma CEA concentration decreases following surgical removal of tumour. A subsequent rise suggests recurrence. However, recurrence is not always accompanied by a rise in plasma CEA levels.
Carcinogen A substance capable of inducing cancer in an organism.
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