Krebs cycle begins with reaction

Options

A. Citric acid + Acetyl CoA
B. Oxaloacetic acid + Pyruvic acid
C. Oxaloacetic acid + Citric acid
D. Oxaloacetate + Acetyl CoA

Answer

### Step-by-Step Solution:

1. **Understanding the Krebs Cycle**: The Krebs cycle, also known as the tricarboxylic acid (TCA) cycle or citric acid cycle, is a crucial metabolic pathway that occurs in the mitochondria of cells during aerobic respiration. It plays a significant role in energy production.

2. **Identifying the Starting Point**: The Krebs cycle begins with a specific reaction involving two key molecules: acetyl-CoA and oxaloacetate.

3. **Formation of Citric Acid**: When acetyl-CoA combines with oxaloacetate, it forms citric acid (also known as citrate). This reaction marks the initiation of the Krebs cycle.

4. **Reviewing the Options**: The options provided in the question are:
- A) Citric acid plus acetyl-CoA
- B) Oxaloacetic acid plus spiroic acid
- C) Oxaloacetic acid plus citric acid
- D) Oxaloacetate plus acetyl-CoA

5. **Selecting the Correct Answer**: Among the given options, the correct reaction that initiates the Krebs cycle is:
- **D) Oxaloacetate plus acetyl-CoA**.

### Final Answer:
The Krebs cycle begins with the reaction of **oxaloacetate plus acetyl-CoA**.

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