activation definition biology
activation. 1. the act or process of rendering active. 2. the transformation of a proenzyme into an active enzyme by the action of a kinase or another enzyme. 3. the process by which the central nervous system is stimulated into activity through the mediation of the reticular activating system. Activation energy. Definition. noun. The amount of energy (in joules) needed to convert all the molecules in one mole of a reacting substance from a ground state to the transition state intermediate. Supplement. The activation energy is a term coined by the Swedish scientist, Svante Arrhenius in 1889. Complement is a group of at least 20 distinct serum proteins, the activity of which is affected by a series of interactions resulting in enzymatic cleavages; it can follow one or the other of at least two pathways. The activation energy of a reaction may be denoted by Ea. In relation to biology (such as biochemistry), the activation energy (or energy of activation) pertains to the energy needed to initiate a reaction. For instance, the activation energy required to breakdown glucose into pyruvic acid in respiration is two ATP. activation. the process of activating. activation analysis. a method of analyzing the content of elements in samples of biological material. The sample is bombarded with nuclear particles and the elements in it measured by the radiation emitted by their radioactive daughter products. Called also radioactivation analysis. activation energy. the difference in energy between the ground state of the reactants in a reaction and the point of maximum energy or transition state of the reactions. Usually lowered by enzyme catalysts. contact activation initiation of the intrinsic pathway of coagulation through interaction of coagulation factor XII with various electronegative surfaces. complement cascade. the sequence of reactions, each being the catalyst for the next, that leads to the terminal complement pathway and cell lysis. There are two pathways for activation of C3, the 'classical' (below) and the 'alternate' (above). See: activation product, activation analysis. Please contribute to this project, if you have more information about this term feel free to edit this page. This page was last modified on 3 October 2005, at 21:16.This page has been accessed 9,984 times. In the first, also referred to as the test system, antigen is mixed usually with serial dilutions of a test serum in the presence of complement. If the serum contains antibody, i.e. is positive, an antibody-antigen complex is formed which also binds (fixes) complement. In the second stage, also called the indicator system, sheep red blood cells coated with specific, usually rabbit anti-sheep red blood cell antibody are added.
The transformation of a proenzyme into an active enzyme by the action of a kinase or another enzyme.