Select the correct statement.

Options

A. When ATP is synthesised directly from metabolites, it is substrate level phosphorylation.
B. In Krebs' cycle, citrate undergoes 2 decarboxylations and 4 dehydrogenations.
C. Krebs' cycle in an amphibolic process.
D. All of these

Answer

To solve the question "Select the correct statement," we will analyze each statement provided in the video transcript step by step.

### Step 1: Analyze the First Statement
The first statement claims that "ATP is synthesized directly from the metabolized substrate; it is substrate-level phosphorylation."
- **Explanation**: This statement is true. Substrate-level phosphorylation occurs during glycolysis when a phosphate group is transferred from a substrate to ADP to form ATP. For example, during the conversion of phosphoenolpyruvate to pyruvic acid, ATP is generated from ADP and inorganic phosphate.

### Step 2: Analyze the Second Statement
The second statement says that "the Krebs cycle citrate undergoes 2D carboxylation and 4D hydrogenation."
- **Explanation**: This statement is also true. In the Krebs cycle, citrate undergoes decarboxylation (removal of carbon dioxide) and dehydrogenation (removal of hydrogen) as it is converted into different intermediates. Specifically, two decarboxylation and four dehydrogenation reactions occur for each acetyl-CoA that enters the cycle.

### Step 3: Analyze the Third Statement
The third statement claims that "the Krebs cycle is an amphibolic process."
- **Explanation**: This statement is true as well. The Krebs cycle is considered amphibolic because it involves both catabolic and anabolic pathways. It breaks down substrates (catabolism) to produce energy while also providing intermediates for biosynthetic processes (anabolism).

### Conclusion
After analyzing all three statements, we find that:
1. The first statement is true.
2. The second statement is true.
3. The third statement is true.

Thus, the correct answer to the question is that **all of these statements are true**.

### Final Answer
**All of these statements are correct.**

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