Question

Which of the following statements are correct with reference to the ionic forms at physiological pH
(A). Phosphatidyl ethanolamine is zwitter ionic.
(B). Phosphatidyl choline is cationic.
(C). Phosphatidyl serine is anionic.
(D). Cardiolipin is anionic.
Choose the correct answer from the options given below:

• A. (A), (B) and (D) only.
• B. (A), (C) and (D) only.
• C. (B), (C) and (D) only.
• D. (C) and (D) only.

Hint:

At physiological pH:
- Zwitterionic (Net charge = 0): Phosphatidylcholine (PC), Phosphatidylethanolamine (PE)
- Anionic (Net charge = negative): Phosphatidylserine (PS), Phosphatidylinositol (PI), Cardiolipin

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
At physiological pH (approximately \(7.4\)), the head groups of membrane glycerophospholipids ionize, giving each lipid a specific net electrical charge.

Step 2: Detailed Explanation:
- Phosphatidyl choline (B): Contains a negatively charged phosphate group and a positively charged quaternary ammonium (choline) group, yielding a net charge of 0 (zwitterionic), not cationic.
- Phosphatidyl ethanolamine (A): Contains a negatively charged phosphate and a positively charged primary amine (ethanolamine) group, resulting in a net charge of 0 (zwitterionic). This statement is correct.
- Phosphatidyl serine (C): Contains a negatively charged phosphate, a negatively charged carboxylate group, and a positively charged amino group, resulting in a net charge of \(-1\) (anionic). This statement is correct.
- Cardiolipin (D): Consists of a double phospholipid structure containing two negatively charged phosphate groups, giving it a net charge of \(-2\) (anionic). This statement is correct.
- Therefore, statements (A), (C), and (D) are correct.

Step 3: Final Answer:
The correct combination is (A), (C) and (D) only.