Which does not occur in cell membrane

Options

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

Answer

To solve the question "Which does not occur in cell membrane?", we can follow these steps:

### Step-by-Step Solution:

1. **Understand the components of the cell membrane**:
The cell membrane is primarily composed of a lipid bilayer, which includes various types of molecules.

2. **Identify the common components of the cell membrane**:
The main components found in the cell membrane include:
- **Phospholipids**: These form the basic structure of the membrane.
- **Cholesterol**: This molecule helps to stabilize the membrane's fluidity.
- **Glycoproteins**: These are proteins with carbohydrate groups attached and play roles in cell recognition and signaling.

3. **Analyze the options provided**:
The options given are:
- Cholesterol
- Phospholipids
- Glycoprotein
- Proline

4. **Determine which option does not belong**:
- Cholesterol, phospholipids, and glycoproteins are all integral parts of the cell membrane.
- Proline, however, is an amino acid that is primarily involved in protein synthesis and is not a component of the cell membrane.

5. **Conclude the answer**:
Based on the analysis, the correct answer is **Proline**, as it does not occur in the cell membrane.

### Final Answer:
The correct option is **Proline**.

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