Question

Define the terms (a) Active site (b) Turn over number (c) Non-competitive Inhibition (d) Isoenzyme (e) Zygmogen (f) Activation energy.

Answer 1

Active site is the part of an enzyme where the catalytic activity on the substrate takes place or active site can be also defined as, it is a region on an enzyme that binds to a protein or other substance during a reaction.

The turnover number can be defined as the number of substrate molecules converted into product per unit time ,when the enzyme is fully saturated with substrate. The value of turn over number varies with different enzymes and depends upon the conditions in which the reaction is taking place.

Non-competitive inhibition can bind to an enzyme with or without a substrate at different places at the same time. It changes the conformation of an enzyme as well as its active site, which makes the substrate unable to bind to the enzyme effectively so that the efficiency decreases.
Isoenzyme is enzyme that differs in amino acid sequence but catalyzes the same chemical reaction orisoenzyme is an enzyme that catalyzes the same reaction but may be differentiated by variation in physical properties such as, isoelectric point, electrophoretic mobility, kinetic parameters or modes of regulation.

Zygmogen is an inactive protein precursor of an enzyme secreted by living cells and converted into an active form. It is also called as a proenzyme. A zymogen requires a biochemical change (such as a hydrolysis reaction revealing the active site, or changing the configuration to reveal the active site) for it to become an active enzyme.

Activation energy is the least amount of energy required to activate atoms or molecules to a state in which they can undergo a chemical reaction. Activation energy is denoted by E_a and typically has units of kilojoules per mole (kJ/mol) or kilocalories per mole (kcal/mol). The term "activation energy" was introduced by the Swedish scientist Svante Arrhenius in 1889.