How many molecules of `CO_(2)` are released during two turns of Krebs cycle ?

Options

A. 2
B. 6
C. 4
D. 3

Answer

To determine how many molecules of CO2 are released during two turns of the Krebs cycle, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Krebs Cycle**: The Krebs cycle, also known as the citric acid cycle or tricarboxylic acid (TCA) cycle, begins with the combination of acetyl coenzyme A (2 carbon) and oxaloacetic acid (4 carbon) to form citric acid (6 carbon).

2. **Decarboxylation Steps**: During one turn of the Krebs cycle, two molecules of CO2 are released. This occurs during the conversion of isocitrate to alpha-ketoglutarate and then from alpha-ketoglutarate to succinyl coenzyme A. Each of these steps involves the removal of one CO2 molecule.

3. **Calculating for Two Turns**: Since each turn of the Krebs cycle releases 2 molecules of CO2, for two turns, we multiply:
\[ 2 \text{ CO2 (per turn)} \times 2 \text{ turns} = 4 \text{ CO2} \]

4. **Conclusion**: Therefore, the total number of CO2 molecules released during two turns of the Krebs cycle is 4.

### Final Answer:
**4 molecules of CO2 are released during two turns of the Krebs cycle.**

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