Question

Lecithin's constituents are

• A. Glycerol and fatty acid
• B. Glycerol, fatty acid, and phosphoric acid
• C. Glycerol, fatty acid, phosphoric acid and choline
• D. Glycerol, fatty acid and carbohydrate

Hint:

Lecithin Formula: Glycerol $+ 2$ Fatty Acids $+$ Phosphate $+$ Choline. (Cephalin replaces choline with Ethanolamine).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Phosphatidylcholine (lecithin) is a major zwitterionic membrane phosphoglyceride consisting of a glycerol backbone, two fatty acids, a phosphate group, and a choline base.
Key Formula or Approach:
\[ \text{Lecithin (Phosphatidylcholine)} = \text{Glycerol} + 2\text{ Fatty Acids} + \text{Phosphoric Acid} + \text{Choline } [-\text{CH}_2-\text{CH}_2-\text{N}^+(\text{CH}_3)_3] \]

Step 2: Detailed Explanation:
Chemical constituents of Lecithin (Phosphatidylcholine):
1. Glycerol Backbone: A 3-carbon trihydroxy alcohol.
2. Two Fatty Acids: Esterified to the $sn-1$ (usually saturated) and $sn-2$ (usually unsaturated) positions.
3. Phosphoric Acid: Esterified to the $sn-3$ hydroxyl group, forming phosphatidic acid.
4. Choline Base: A positively charged nitrogenous base linked via a phosphodiester bond to the phosphate group.

Step 3: Final Answer:
Therefore, Lecithin's constituents are Glycerol, fatty acid, phosphoric acid and choline, corresponding to option (C).