| active site | <chemistry> A specific region of an enzyme where a substrate binds and catalysis takes place (binding site). (06 May 1997) |
|---|---|
| active splint | A splint utilizing springs or elastic bands that aids in movements initiated by the patient by controlling the plane and range of motion. Synonym: active splint, functional splint. (05 Mar 2000) |
| active succinate | The condensation product of succinic acid and CoA; one of the intermediates of the tricarboxylic acid cycle and a precursor in the synthesis of haem. Synonym: active succinate, succinyl-CoA. (05 Mar 2000) |
| active sulfate | 3'-phosphoadenosine 5'-phosphosulfate;an intermediate in the formation of urinary ethereal sulfates, notable for containing a "high energy" sulfate bond; the 3'-OH of adenosine is replaced by -OPO3H2, the 5'-OH by -OP(O2H)-OSO3H. Synonym: active sulfate. Acronym: PAPS (05 Mar 2000) |
| active transport | <biochemistry, chemistry> Transport of ions, nutrients or other molecules into a cell against a concentration gradient, this requires the expenditure of energy through ATP hydrolysis. (06 May 1997) |
| active treatment | A therapeutic substance or course intended to ameliorate the basic disease problem, as opposed to supportive or palliative treatment. Compare: causal treatment. (05 Mar 2000) |
| active vasoconstriction | Reduced caliber of a vessel caused by increased tonus in the smooth muscle in its walls. (05 Mar 2000) |
| active vasodilation | Vasodilation caused by decrease in tonus of smooth muscle in the wall of a vessel. (05 Mar 2000) |
| artificial active immunity | See: acquired immunity. (05 Mar 2000) |
| biological transport, active | The movement of materials across cell membranes and epithelial layers against an electrochemical gradient, requiring the expenditure of metabolic energy. (12 Dec 1998) |
| specific active immunity | See: acquired immunity. (05 Mar 2000) |
| surface-active | Indicating the property of certain agents of altering the physicochemical nature of surfaces and interfaces, bringing about lowering of interfacial tension; they usually possess both lipophilic and hydrophilic groups. See: surfactant. (05 Mar 2000) |
| surface-active agent | Agents that modify interfacial tension of water; usually substances that have one lipophilic and one hydrophilic group in the molecule; includes soaps, detergents, emulsifiers, dispersing and wetting agents, and several groups of antiseptics. (12 Dec 1998) |
| surface active compound | <biochemistry> Usually, in biological systems, means a detergent like molecule that is amphipathic and that will bind to the plasma membrane or to a surface with which cells come in contact, altering its properties from hydrophobic to hydrophilic or vice versa. (18 Nov 1997) |
| immunity, active | Resistance to a disease agent resulting from the production of specific antibodies by the host, either after exposure to the disease or after vaccination. (12 Dec 1998) |