Lecithin is a

Options

A. sterol
B. glycolipid
C. phospholipid
D. sphingolipid.

Explanation

**Step-by-Step Solution:**

1. **Understanding Lecithin**: Lecithin is a compound that is being examined in the context of biomolecules. It is important to identify its chemical classification.

2. **Identifying the Structure**: Lecithin is classified as a phospholipid. This means it contains a phosphate group as part of its structure.

3. **Analyzing the Components**: Lecithin is a diglyceride, which means it has two fatty acid chains attached to a glycerol backbone. Additionally, it contains a nitrogen-containing group known as choline.

4. **Function of Lecithin**: Lecithin plays a crucial role in biological systems. It is a key component of cell membranes (plasma membranes) and is also found in the alveolar walls of the lungs, where it functions as a surfactant to help increase surface area.

5. **Eliminating Other Options**:
- It is not a sterol (like cholesterol).
- It is not a glycolipid since it specifically contains a phosphate group.
- It is also not a sphingolipid, which is associated with the myelin sheath.

6. **Conclusion**: Based on the information gathered, lecithin is best classified as a phospholipid.

**Final Answer**: Lecithin is a phospholipid.

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