Question

describe the role of enzymes in the catalysis of biological reactions (include in the discussion substrate, product, active site, lock and key model, activation energy, enzyme substrate complex, and transition state complex, and steps of enzyme action)?

Answer 1

A substance that speeds up a chemical reaction without being a reactant is called a catalyst. The catalysts for biochemical reactions that happen in living organisms are called enzymes. Enzymes are usually proteins, some ribonucleic acid (RNA) molecules also act as enzymes too.

The enzyme converts the substrates into different molecules known as products.

Active site is the region of the enzyme where the substrate (and cofactor if any) binds and catalysis occur.  

Lock and key model assume that a high degree of complementary between the shape of the substrate and the geometry of the binding site on an enzyme. The complementary between enzymes and their substrates is the basis of the lock and key model of enzyme function. This model was first proposed by Emil Fischer in 1984.

Activation is the amount of energy that must be put in for the reaction to begin. Enzymes work by binding to reactant molecules and holding them in such a way that the chemical bond-breaking and bond-forming processes take place more readily.

The enzyme-substrate complex is a temporary molecule formed when an enzyme comes into perfect contact with its substrate. Without its substrate, an enzyme is a slightly different shape. The substrate causes a conformational change, or shape change when the substrate enters the active site.The active site is the area of the enzyme capable of forming weak bonds with the substrate. This shape change can force two or more substrate molecules together, or split individual molecules into smaller parts.

Transition state is an unstable state that products must pass through in order to become reactants. The transition state is at the top of the energy "hill". The transition state is the state corresponding to the highest energy along the reaction coordinate. It has more free energy in comparison to the substrate or product. The specific form of the transition state depends on the mechanisms of the particular reaction.

There are Four Steps of Enzyme Action

1. The enzyme and the substrate are in the same area. Some situations have more than one substrate molecule that the enzyme will change.
2. The enzyme grabs on to the substrate at a special area called the active site.
3. A process called catalysis happens
4. The enzyme releases the product.