Which is not a lipid ?
(a) Lecithin
(b) β- keratin
(c) Sterol
(d) wax

Options

A. Lecithin
B. `beta` - keratin - protein
C. Sterol
D. wax

Answer

To determine which of the following options is not a lipid, we need to analyze each option based on the characteristics of lipids.

1. **Understanding Lipids**:
- Lipids are macromolecules that typically have a polar hydroxyl group and a nonpolar character due to long hydrocarbon chains or fatty acids. They include fats, oils, waxes, and sterols.

2. **Analyzing the Options**:
- **(a) Lecithin**: Lecithin is a phospholipid, which is a type of lipid. It contains fatty acids and is important in cell membrane structure.
- **(b) β-carotene**: β-carotene is a pigment found in plants and is a precursor to vitamin A. It is not a lipid; it is classified as a carotenoid, which is a type of terpenoid.
- **(c) Sterol**: Sterols, such as cholesterol, are a class of lipids characterized by a multi-ring structure. They are indeed lipids.
- **(d) Wax**: Waxes are long-chain fatty acids esterified to long-chain alcohols, making them a type of lipid.

3. **Conclusion**:
- Based on the analysis, the only option that is not a lipid is **(b) β-carotene**.

Thus, the correct answer is **(b) β-carotene**.