Assertion : During aerobic respiration, pyruvic acid formed as a result of glycolysis, undergoes phosphorylation reaction to form acetyl CoA.
Reason : There is net gain of 18 ATP molecules during aerobic respiration of one molecule of glucose.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion
B. If both assertion and reason are true but reason is not the correct explanation of assertion
C. If assertion is true but reason is false
D. If both assertion and reason are false

Explanation

To analyze the assertion and reason provided in the question, we will break down the concepts step by step.

### Step 1: Understand the Assertion
The assertion states: "During aerobic respiration, pyruvic acid formed as a result of glycolysis undergoes phosphorylation reaction to form acetyl CoA."

- **Explanation**: In aerobic respiration, pyruvic acid is indeed produced from glycolysis. However, the process that converts pyruvic acid to acetyl CoA is not a phosphorylation reaction; it is an oxidative decarboxylation reaction. During this process, pyruvic acid loses a carbon atom (in the form of CO2) and is combined with coenzyme A to form acetyl CoA.

### Step 2: Understand the Reason
The reason states: "There is a net gain of 18 ATP molecules during aerobic respiration of one molecule of glucose."

- **Explanation**: The complete oxidation of one molecule of glucose during aerobic respiration typically yields a net gain of about 36 ATP molecules, not 18. This includes ATP produced during glycolysis, the Krebs cycle, and oxidative phosphorylation. Therefore, this statement is also incorrect.

### Step 3: Conclusion
Since both the assertion and the reason are incorrect, we conclude that:

- **Assertion**: False (pyruvic acid undergoes oxidative decarboxylation, not phosphorylation).
- **Reason**: False (the net gain is approximately 36 ATP, not 18).

### Final Answer
Both the assertion and reason are false.

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