Cell membrane is chemically composed by

Options

A. Lipids
B. Carbohydrates
C. Proteins
D. All the above

Answer

### Step-by-Step Solution:

1. **Understanding the Composition of the Cell Membrane**:
- The cell membrane is a vital structure that surrounds the cell, providing protection and support. It is composed of various biomolecules.

2. **Identifying the Main Components**:
- The primary components of the cell membrane include:
- **Lipids**: These are the main structural components, forming a bilayer.
- **Proteins**: These are embedded within the lipid bilayer and perform various functions, including transport and signaling.
- **Carbohydrates**: These are present in smaller amounts and are often attached to proteins and lipids, playing roles in cell recognition and communication.

3. **Percentage Composition**:
- The composition of these components can vary:
- **Proteins**: 20% to 70%
- **Lipids**: 29% to 79%
- **Carbohydrates**: 1% to 5%
- Water is also a component but is not a structural part of the membrane.

4. **Understanding the Structure**:
- The cell membrane is structured as a bilayer, where:
- The **polar heads** of the lipids face outward towards the aqueous environment.
- The **non-polar tails** face inward, away from water.
- Proteins can be found within this bilayer, serving as channels or receptors.

5. **Conclusion**:
- The cell membrane is chemically composed of lipids, proteins, and carbohydrates. Therefore, the correct answer to the question is "all of the above."

### Final Answer:
The cell membrane is chemically composed of lipids, carbohydrates, and proteins (Option: All of the above).

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