Which type of molecule does pepsin digest?

Options

A. Fat
B. starch
C. Protein
D. Lipid

Answer

**Step-by-Step Solution:**

1. **Identify Pepsin**: Pepsin is an enzyme that plays a crucial role in the digestion of proteins in the stomach.

2. **Understand the Function of Pepsin**: Pepsin is classified as an endopeptidase. This means that it breaks down proteins by cleaving the peptide bonds within the protein chain, rather than at the ends (which would be the function of exopeptidases).

3. **Source of Pepsin**: Pepsin is secreted in the stomach as part of gastric juice, specifically produced by chief cells in the gastric lining.

4. **Activation of Pepsin**: Pepsin is initially secreted in an inactive form called pepsinogen. It is activated to pepsin in the acidic environment of the stomach.

5. **Substrate of Pepsin**: Pepsin primarily digests proteins, breaking them down into smaller peptides.

6. **Evaluate Options**: Given the options:
- FAT: Incorrect, as pepsin does not digest fats.
- STARCH: Incorrect, as starch is digested by amylase, not pepsin.
- PROTEIN: Correct, as pepsin digests proteins.
- LIPIDS: Incorrect, as pepsin does not digest lipids.

7. **Conclusion**: The type of molecule that pepsin digests is **protein**.

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