Medium in which pepsin is active

Options

A. neutral
B. alkaline
C. acidic
D. isotonic

Explanation

**Step-by-Step Solution:**

1. **Understanding Pepsin**: Pepsin is an enzyme that plays a crucial role in the digestion of proteins. It is secreted in an inactive form called pepsinogen and is activated in the stomach.

2. **Identifying the Medium**: To determine the medium in which pepsin is active, we need to understand the pH levels associated with different mediums:
- **Neutral**: A neutral medium has a pH of 7, meaning it is neither acidic nor basic.
- **Alkaline**: An alkaline medium has a pH greater than 7, indicating it is basic.
- **Acidic**: An acidic medium has a pH less than 7.
- **Isotonic**: Isotonic refers to a solution where the concentration of solutes is the same as another solution, which is not directly related to pH.

3. **Pepsin Activation**: Pepsin is most active in an acidic environment, specifically within a pH range of approximately 1.5 to 2.5. This indicates that pepsin functions optimally in a strongly acidic medium.

4. **Conclusion**: Since pepsin is activated in an acidic medium (pH < 7), we conclude that the correct answer to the question is "acidic".

**Final Answer**: The medium in which pepsin is active is acidic.

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