Phospholipids are esters of glycerol with
(a)one carboxylic acid residue and two phosphate groups
(b)three phosphate groups
(c)three carboxylic acid residues
(d)two carboxylic acid residues and one phosphate group

Options

A. one carboxylic acid residue and two phosphate groups
B. three phosphate groups
C. three carboxylic acid residues
D. two carboxylic acid residues and one phosphate group

Explanation

To solve the question about phospholipids, we need to understand their structure and components. Let's break it down step by step.

### Step-by-Step Solution:

1. **Understanding Phospholipids**:
- Phospholipids are a type of lipid molecule that are essential components of cell membranes. They consist of a glycerol backbone, fatty acid tails, and a phosphate group.

2. **Identifying Components**:
- Phospholipids are esters formed from glycerol and fatty acids. Specifically, they are formed from glycerol (which has three hydroxyl groups) and two fatty acids (which are carboxylic acids).

3. **Analyzing the Options**:
- (a) One carboxylic acid residue and two phosphate groups: This is incorrect because phospholipids have two fatty acids, not one, and only one phosphate group.
- (b) Three phosphate groups: This is incorrect as phospholipids only contain one phosphate group.
- (c) Three carboxylic acid residues: This is incorrect because phospholipids only have two carboxylic acid residues from the two fatty acids.
- (d) Two carboxylic acid residues and one phosphate group: This is correct as phospholipids are indeed composed of two fatty acids (each contributing one carboxylic acid) and one phosphate group.

4. **Conclusion**:
- Based on the analysis of the options, the correct answer is (d) two carboxylic acid residues and one phosphate group.

### Final Answer:
**(d) two carboxylic acid residues and one phosphate group**