Question

Determine the correctness or otherwise of the following Assertion [a] and the Reason [r]. Assertion [a]: On a per carbon basis, palmitic acid yields more ATP than glucose.
Reason [r]: Carbons in palmitic acid are more reduced than those in glucose.

• A. Both [a] and [r] are true and [r] is the correct reason for [a]
• B. Both [a] and [r] are true but [r] is not the correct reason for [a]
• C. [a] is true but [r] is false
• D. [a] is false but [r] is true

Hint:

Always compare ATP yield on a per-carbon basis when analyzing carbohydrate vs fat metabolism. Fatty acids usually yield more energy because their carbons are more reduced.

Answer 1

The Correct Option is A

Step 1: Energy yield from glucose vs palmitic acid
- Glucose (6 carbons) produces $\approx$ 30–32 ATP after complete oxidation $⇒$ $\approx 5.2$ ATP per carbon.
- Palmitic acid (16 carbons) produces $\approx$ 106 ATP after complete oxidation $⇒$ $\approx 6.6$ ATP per carbon.
Thus, Assertion [a] is true. Step 2: Reduction state of carbons
- Carbons in fatty acids like palmitic acid are mostly in the reduced (–CH$_2$–) state.
- Carbons in glucose are partially oxidized (due to hydroxyl groups).
- More reduced carbons release more electrons during oxidation, generating more ATP.
Thus, Reason [r] is true and directly explains [a]. Therefore, the correct answer is (A).