Chapter 6.5, Problem 11SAQ

Summary Introduction

To describe:

The role of enzymes in chemical reactions in cell and their three characteristics.

Introduction:

Enzymes are chemical catalyst which accelerate a chemical reaction in a cell. The catalyst is a chemical substance or protein that causes increase in the rate of reaction without being affected in small time.

Explanation of Solution

Enzymes accelerate a chemical reaction by increasing the reaction rate and decreasing the activation energy. Reaction rate of a chemical reaction is needed for the formation of product, which is influenced by enzymes. It speeds up the chemical reaction.

All the chemical reactions need an input of energy for processing which is termed as activation energy $(\text{EA})$. It is the input of energy which is required to reach a transition state during a chemical reaction. It results in increase in speed of a reaction, formation of products and release of energy into the surroundings. It does not change free energy but it changes the way of the reaction. The starting and the end point of the reaction remain same.

There are various characteristics of enzymes. Three of them are as follows:

1. i. In a chemical reaction, enzyme causes the formation of a complex that contains reactants and products. The substrate (S) is a reactant in a reaction that is catalyzed by an enzyme (E). It is further converted into product (P) of the reaction.
2. ii. The enzymes that catalyze the rate of reaction of a chemical reaction are highly specific. Enzymes are specific for both substrate and product of a chemical reaction.
3. iii. The activity of enzyme in a reaction can be influenced by activators and inhibitors. The activator causes increase in the activity of an enzyme, while inhibitor decreases the activity of an enzyme in a chemical reaction.

Conclusion

The enzymes are intermediate molecules that permit the chemical reaction to occur in a cell.