Enzymes are divided into different classes based on the type of

Options

A. 1)Substrate they act
B. 2)Type of reaction they catalyse
C. 3)On reaction mechanism
D. 4)None of the above

Answer

### Step-by-Step Solution:

1. **Understanding Enzymes**: Enzymes are biological catalysts that speed up chemical reactions in living organisms. They are crucial for various metabolic processes.

2. **Classification of Enzymes**: Enzymes are classified into different classes based on specific criteria. The question asks about the basis for this classification.

3. **Analyzing the Options**:
- **Option A: Substrate** - This option suggests that enzymes are classified based on the substrate they act upon. While substrates are important, they do not serve as the primary basis for enzyme classification.
- **Option B: Type of Reaction They Catalyze** - This option indicates that enzymes are classified according to the type of reactions they facilitate. This is a well-established method of classification.
- **Option C: Reaction Mechanism** - This option implies that enzymes are classified based on how they catalyze reactions. While mechanisms are important, they are not the primary classification method.
- **Option D: None of the Above** - This option suggests that none of the previous options are correct, which is not the case.

4. **Correct Classification Method**: The correct basis for classifying enzymes is indeed the type of reaction they catalyze. There are six main classes of enzymes based on this criterion:
- **Oxidoreductases**: Enzymes that catalyze oxidation-reduction reactions.
- **Transferases**: Enzymes that transfer functional groups from one molecule to another.
- **Hydrolases**: Enzymes that catalyze hydrolysis reactions (breaking down compounds with the addition of water).
- **Lyases**: Enzymes that catalyze the addition or removal of groups to form double bonds.
- **Isomerases**: Enzymes that catalyze the rearrangement of molecules.
- **Ligases**: Enzymes that catalyze the joining of two molecules with the use of ATP.

5. **Conclusion**: Based on the analysis, the correct answer to the question is **Option B: Type of Reaction They Catalyze**.