Which one of the following is not a constituent of cell membrane

Options

A. Proline
B. Phospholipids
C. Cholesterol
D. Glycolipids

Answer

To determine which of the following options is not a constituent of the cell membrane, follow these steps:

### Step-by-Step Solution:

1. **Understand the Composition of the Cell Membrane**:
- The cell membrane is primarily composed of phospholipids, proteins, cholesterol, and glycolipids.

2. **Analyze the Given Options**:
- The options provided include various substances. We need to identify which one is not a part of the cell membrane.

3. **Identify Each Component**:
- **Phospholipids**: These are the main building blocks of the cell membrane, forming a bilayer.
- **Proteins**: These can be integral (spanning the membrane) or peripheral (attached to the surface).
- **Cholesterol**: This molecule helps to stabilize the membrane fluidity.
- **Glycolipids**: These are lipids with carbohydrate groups attached, contributing to cell recognition and signaling.

4. **Evaluate the Options**:
- If one of the options is proline, we need to assess its role. Proline is an amino acid but is not a structural component of the cell membrane.

5. **Conclusion**:
- Since proline does not form part of the cell membrane structure, it is the correct answer to the question. Therefore, the option that is not a constituent of the cell membrane is **proline**.

### Final Answer:
- The correct option that is not a constituent of the cell membrane is **proline**.