Cell membrane is composed of

Options

A. Phospholipid
B. Nucleoprotein
C. Polysaccharides
D. Lipoprotein

Answer

### Step-by-Step Solution:

1. **Understanding the Cell Membrane**:
- The cell membrane, also known as the plasma membrane, is a vital structure that surrounds the cell, providing protection and regulating what enters and exits the cell.

2. **Composition of the Cell Membrane**:
- The primary component of the cell membrane is the **lipid bilayer**. This bilayer is mainly composed of **phospholipids**.

3. **Structure of Phospholipids**:
- Each phospholipid molecule consists of:
- A **hydrophilic (water-attracting) head**: This part is polar and contains a phosphate group.
- Two **hydrophobic (water-repelling) tails**: These are nonpolar lipid chains.

4. **Amphipathic Nature**:
- The phospholipids are described as **amphipathic** because they have both hydrophilic and hydrophobic parts. This unique property allows them to form a bilayer in an aqueous environment, with the hydrophilic heads facing outward towards the water and the hydrophobic tails facing inward, away from the water.

5. **Proteins in the Cell Membrane**:
- In addition to phospholipids, the cell membrane contains various **proteins**. These proteins can be:
- **Extrinsic (peripheral) proteins**: Located on the outer or inner surface of the membrane.
- **Intrinsic (integral) proteins**: Embedded within the lipid bilayer.

6. **Conclusion**:
- Based on the composition discussed, the correct answer to the question "Cell membrane is composed of" is **phospholipids**. Other options such as nucleoprotein, polysaccharides, and lipoprotein are incorrect in this context.