Lecithin and cephalins are

Options

A. nucleic acid
B. phospholipid
C. carbohydrate
D. sphingolipids

Answer

### Step-by-Step Solution:

1. **Understanding the Context**: Lecithin and cephalins are types of phospholipids. Phospholipids are essential components of cell membranes, which serve to protect the cell and regulate the movement of substances in and out of the cell.

2. **Identifying the Components of Cell Membrane**: The cell membrane is primarily composed of lipids, proteins, carbohydrates, and cholesterol. Among these, lipids play a crucial role in forming the bilayer structure of the membrane.

3. **Defining Lecithin and Cephalins**:
- **Lecithin**: This is a type of phospholipid that contains the amino alcohol choline. Lecithin is important for maintaining the structural integrity of cell membranes and is involved in various cellular functions.
- **Cephalins**: These are also phospholipids but contain the amino alcohol serine. Cephalins play a similar role in cell membranes and are involved in various cellular processes.

4. **Differentiating Between Lecithin and Cephalins**: The primary difference between lecithin and cephalins lies in their amino alcohol component:
- Lecithin = Contains choline
- Cephalins = Contains serine

5. **Conclusion**: Both lecithin and cephalins are phospholipids that contribute to the structure and function of cell membranes, but they differ in their specific amino alcohol components.