The concept that explains how the large quantity of substrate is acted upon by a small concentration enzyme is

Options

A. Coenzyme theory
B. Enzyme collision theory
C. Induced fit theory
D. Lock and key theory

Answer

To solve the question regarding the concept that explains how a large quantity of substrate is acted upon by a small concentration of enzyme, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for a theory that describes the interaction between a large number of substrates and a small number of enzymes.

2. **Analyzing the Options**:
- **Coenzyme Theory**: This theory involves non-protein molecules that assist enzymes in catalyzing reactions. It does not specifically address the ratio of substrate to enzyme.
- **Enzyme Collision Theory**: This theory focuses on how enzymes and substrates collide to form products. It does not specifically explain the large quantity of substrate acting on a small number of enzymes.
- **Induced Fit Theory**: This theory states that the binding of a substrate induces a change in the enzyme's structure, enhancing the fit between the enzyme and substrate. While it describes enzyme-substrate interaction, it does not specifically address the quantity relationship.
- **Lock and Key Theory**: This theory describes how substrates fit into enzymes like a key fits into a lock. It implies that a small number of enzymes can effectively interact with a large number of substrates due to the specific nature of the enzyme's active site.

3. **Identifying the Correct Theory**: Among the options, the **Lock and Key Theory** best explains how a small concentration of enzymes can act on a large quantity of substrates. This theory emphasizes the specificity of the enzyme's active site and how it can accommodate multiple substrate molecules.

4. **Conclusion**: The correct answer to the question is the **Lock and Key Theory**, as it effectively describes the interaction between a small number of enzymes and a large quantity of substrates.