Question

Describes extensively the action of enzymes. (Bibliography)

Answer 1

Enzymes are defined as Biological catalyst which can increase the speed of a chemical reaction. The key feature that distinguishes an enzyme (Biological catalyst) from other catalysts, is that that enzymes are specific. This specificity of enzymes is because of the presence of an active site where the substrate molecules binds. All enzymes are proteins (except for Ribozymes which is RNA) and hence they will be made up of long chains of amino acids. And the active site of enzyme also pocess certain amino acids that are capable of interacting with side chains of its substrate molecule. In other words, active site and and the substrate molecule should be complementary so that a specific enzyme can bind only on a specific substate molecule, to catalyse the chemical reaction (ie., unique geometrical shape of an enzyme is complementary to the geometric shape of the substarte).

Enzymes act by reducing the Activation energy (Ea). It is the energy barrier that is required to overcome for a chemical reaction to occur. The principle behind enzyme catalysis is binding energy. It is the sum of the energy released during the formation of non covalent interactions between enzymes and substate. This non covalent energy is supplied to the system, so that now the activation energy required by molecules decreases.

Hence all properties of an enzyme can be attributed to binding energy.

The enzyme catalysed reactions can occur in 2 steps.

1) Formation of E-S complex ( Enzyme- substrate complex)

2) THe release of products.

In the first step the enzyme molecule (E) collides with substrate molecule (S) and they react to form an intermediate compound called E-S (Enzyme -Substrate) complex. This is a reverssible step . So this complex can break to release free enzyme and original substrate molecule. Once the E-S complex forms, in the second step, the enzyme is able to catalyse the formation of product (P) which is subsequently released from the enzymes active site. And the enzyme is now free for carrying out a second cycle of catalysis.