What is true of Krebs cycle

Options

A. ATP/GTP is formed
B. Two decarboxylations
C. Acetyl CoA mombines with OAA
D. All the above

Answer

### Step-by-Step Solution:

1. **Understanding the Krebs Cycle**: The Krebs cycle, also known as the citric acid cycle or TCA cycle, is a crucial metabolic pathway that takes place in the mitochondria. It is responsible for the oxidation of acetyl-CoA to produce energy.

2. **Formation of Acetyl-CoA**: Before entering the Krebs cycle, pyruvate, which is produced from glycolysis, is converted into acetyl-CoA. This conversion involves the decarboxylation of pyruvate, releasing carbon dioxide (CO2).

3. **Combination with Oxaloacetic Acid (OAA)**: Acetyl-CoA then combines with oxaloacetic acid (OAA) to form citric acid (citrate), which is the first step of the Krebs cycle.

4. **Energy Production**: Throughout the Krebs cycle, several high-energy molecules are produced, including NADH (Nicotinamide adenine dinucleotide) and FADH2 (Flavin adenine dinucleotide), as well as a small amount of ATP (Adenosine triphosphate) or GTP (Guanosine triphosphate) during the cycle.

5. **Decarboxylation Events**: The Krebs cycle involves multiple decarboxylation reactions, where carbon dioxide is removed from the intermediates, contributing to the overall energy yield of the cycle.

6. **Conclusion**: Therefore, all the statements regarding the Krebs cycle are true: ATP or GTP is formed during decarboxylation, acetyl-CoA combines with OAA, and overall, the cycle produces high-energy molecules.

### Final Answer:
The correct option is "all the above" because:
- ATP or GTP is formed during decarboxylation.
- Acetyl-CoA combines with oxaloacetic acid (OAA).
- The Krebs cycle produces high-energy molecules.

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