Which of these statements about TCA cycle is false ?

Options

A. There are three points in the cycle where `NAD^+` is reduced to NADH + H and one point where FAD + is reduced to `FADH_2`
B. During the conversion of succinyl - CoA to succinic acid a molecule of GTP is synthesized.
C. It involves condensation of acetyl group with oxaloacetate acid (OAA) and water to yield citric acid
D. It involves two steps of decarboxylation, one leads to formation of alpha ketoglutaric acid while the other leads to the formation of succinic acid

Answer

To determine which statement about the TCA cycle (also known as the Krebs cycle) is false, we will analyze each statement provided in the question.

### Step-by-Step Solution:

1. **Understanding the TCA Cycle**: The TCA cycle is a series of biochemical reactions used by all aerobic organisms to generate energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.

2. **Analyzing the Statements**:
- **Statement 1**: "There are three steps in the cycle where NAD+ is reduced to NADH + H+ and one point where FAD+ is reduced to FADH2."
- **Evaluation**: This statement is true. In the TCA cycle, there are indeed three dehydrogenation steps where NAD+ is reduced to NADH, and one step where FAD+ is reduced to FADH2.

- **Statement 2**: "During the conversion of succinyl coenzyme A to succinic acid, a molecule of GDP is synthesized."
- **Evaluation**: This statement is also true. The conversion of succinyl-CoA to succinate involves the phosphorylation of GDP to GTP.

- **Statement 3**: "It involves condensation of acetyl group (acetyl coenzyme A) with oxaloacetic acid, where water is used to yield citric acid."
- **Evaluation**: This statement is true. The first step of the TCA cycle is the condensation of acetyl-CoA with oxaloacetate to form citrate, and water is indeed involved in this reaction.

- **Statement 4**: "It involves two steps of decarboxylation, one leads to formation of alpha-ketoglutaric acid, while the other leads to formation of succinic acid."
- **Evaluation**: This statement is false. While there are two decarboxylation steps in the TCA cycle, the second decarboxylation step leads to the formation of succinyl-CoA, not succinic acid. Succinic acid is formed from succinyl-CoA through a different process (dephosphorylation), not decarboxylation.

3. **Conclusion**: The false statement about the TCA cycle is the fourth statement.

### Final Answer:
The false statement about the TCA cycle is: "It involves two steps of decarboxylation, one leads to formation of alpha-ketoglutaric acid, while the other leads to formation of succinic acid."

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