| mitotic cycle | <cell biology, molecular biology> The sequence of events between mitotic divisions. The cycle is conventionally divided into G0, G1, (G standing for gap), S (synthesis phase during which the DNA is replicated), G2 and M (mitosis). Cells that will not divide again are considered to be in G0 and the transition from G0 to G1 is thought to commit the cell to completing the cycle and dividing. (26 Mar 1998) |
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| combined cycle | Two or more generation processes in series or in parallel, configured to optimise the energy output of the system. (05 Dec 1998) |
| combined-cycle power plant | The combination of a gas turbine and a steam turbine in an electric generation plant. The waste heat from the gas turbine provides the heat energy for the steam turbine. (05 Dec 1998) |
| Cori cycle | The phases in the metabolism of carbohydrate: 1) glycogenolysis in the liver; 2) passage of glucose into the circulation; 3) deposition of glucose in the muscles as glycogen; 4) glycogenolysis during muscular activity and conversion to lactate, which is converted to glycogen in the liver. (05 Mar 2000) |
| hair cycle | The cyclical phases of growth (anagen), regression (catagen), and quiescence (telogen) in the life of a hair. (05 Mar 2000) |
| cycle | A round or succession of observable phenomena, recurring usually at regular intervals and in the same sequence. Origin: Gr. Kyklos = circle (18 Nov 1997) |
| Shemin cycle | A series of metabolic steps in which glycine is condensed with succinyl-CoA and is then oxidised to CO2 and H2O with regeneration of the succinyl-CoA; important in the synthesis of d-aminolevulinic acid and in the metabolism of red blood cells. Synonym: Shemin cycle. (05 Mar 2000) |
| nitrogen cycle | <biochemistry> The global cycle of moving various forms of nitrogen through the air, water, soil, plants, animals of the planet. See: nitrogen fixation. (09 Oct 1997) |
| substrate cycle | <biochemistry> Any seqence of enzyme catalysed reactions in which the forward and reverse processes (catalysed by different enzymes) are consititutively active. Frequently used to describe the cycle of phosphorylation and dephosphorylation of phosphatidyl inositol derivatives in cell membranes. (05 Jan 1998) |
| direct life cycle | <epidemiology> A life cycle in which a parasite is transmitted directly from one host to the next without an intermediate host or vector of another species. (05 Dec 1998) |
| indirect life cycle | <epidemiology> A life cycle which requires one or more intermediate hosts before the definitive host species is reinfected. Compare direct, nondirect. (05 Dec 1998) |
| isometric period of cardiac cycle | That period in which the muscle fibres do not shorten although the cardiac muscle is excited and the pressure in the ventricles rises, extending from the closure of the atrioventricular valves to the opening of the semilunar valves (isovolumic constriction) or the reverse (isovolumic relaxation). (05 Mar 2000) |
| ornithine cycle | The metabolic pathway isfound in vertebrates and takes place in theliver, in it, urea is synthesised from amino acids and carbon dioxide. (09 Oct 1997) |
| ovarian cycle | The normal sex cycle which includes development of an ovarian (graafian) follicle, rupture of the follicle with discharge of the ovum, and formation and regression of a corpus luteum. (05 Mar 2000) |
| TCA cycle | <biochemistry> The central feaure of oxidative metabolism. Cyclic reactions whereby acetyl CoA is oxidized to carbon dioxide providing reducing equivalents (NADH or FADH2) to power the electron transport chain. Also provides intermediates for biosynthetic processes. (16 Dec 1997) |