One molecule of an enzyme is able to catalyse conversion of two molecules of substrate into products in 5 mintutes. Ten molecules of enzyme and 25 molecules of substrate are mixed in a test tube. At the end of 10 minutes the test tube will have

Options

A. products only
B. products and 5 molecules of unreacted substrate
C. products, enzyme and 5 molecules of unreacted substrate
D. products and enzyme

Answer

To solve the problem, we need to analyze the information given and determine the outcome after mixing the specified amounts of enzyme and substrate.

### Step-by-Step Solution:

1. **Understanding the Enzyme-Substrate Relationship**:
- One molecule of enzyme can convert two molecules of substrate into products in 5 minutes.

2. **Calculating the Total Enzyme Capacity**:
- We have 10 molecules of enzyme. Since each enzyme can convert 2 substrate molecules, the total capacity of 10 enzymes in 5 minutes is:
\[ 10 \text{ enzymes} \times 2 \text{ substrate molecules/enzyme} = 20 \text{ substrate molecules} \]

3. **Determining the Available Substrate**:
- We have 25 molecules of substrate available for the reaction.

4. **Identifying the Limiting Factor**:
- Since the enzymes can process a maximum of 20 substrate molecules in 5 minutes, but we have 25 substrate molecules, the enzymes will be the limiting factor. After 5 minutes, 20 substrate molecules will be converted into products, leaving:
\[ 25 \text{ substrate molecules} - 20 \text{ substrate molecules} = 5 \text{ unreacted substrate molecules} \]

5. **Calculating the Reaction After 10 Minutes**:
- After the first 5 minutes, the 10 enzyme molecules will still be available to continue the reaction. However, since there are only 5 unreacted substrate molecules left, the enzymes can only convert these remaining substrates in the next 5 minutes.
- In the next 5 minutes, all 5 remaining substrate molecules will be converted into products, resulting in:
\[ 20 \text{ products (from the first 5 minutes)} + 5 \text{ products (from the second 5 minutes)} = 25 \text{ total products} \]

6. **Final Composition in the Test Tube**:
- At the end of 10 minutes, all 25 substrate molecules will have been converted into products, and since enzymes are not consumed in the reaction, all 10 enzyme molecules will still be present.
- Therefore, the test tube will contain:
- 25 molecules of products
- 10 molecules of enzyme
- 0 molecules of unreacted substrate

### Conclusion:
At the end of 10 minutes, the test tube will have **25 molecules of product and 10 molecules of enzyme**.