Pyruvic acid is formed during

Options

A. Krebs cycle
B. Glycolysis
C. Ornithine cycle
D. Calvin cycle

Answer

### Step-by-Step Text Solution

1. **Understanding the Question**: The question asks about the process during which pyruvic acid is formed.

2. **Analyzing the Options**:
- **Krebs Cycle**: This cycle is involved in aerobic respiration and produces NADH and carbon dioxide, but it does not produce pyruvic acid. Thus, this option is incorrect.
- **Glycolysis**: This is the process that breaks down glucose into pyruvic acid. It is the correct answer as it directly leads to the formation of pyruvic acid.
- **Ornithine Cycle (Urea Cycle)**: This cycle is involved in the conversion of ammonia to urea, and does not produce pyruvic acid. Therefore, this option is incorrect.
- **Calvin Cycle**: This cycle is part of photosynthesis and primarily produces glucose, not pyruvic acid. Hence, this option is also incorrect.

3. **Identifying the Correct Process**: From the analysis, glycolysis is the only process that leads to the formation of pyruvic acid.

4. **Explaining Glycolysis**:
- Glycolysis begins with one molecule of glucose, which is converted into fructose 1,6-bisphosphate. This step requires the investment of two ATP molecules, hence it is called the energy investment phase.
- Following this, the fructose 1,6-bisphosphate is split into two molecules of glyceraldehyde 3-phosphate (G3P).
- The G3P molecules are then converted into pyruvic acid (or pyruvate) through a series of enzymatic reactions.
- During this conversion, energy is released, resulting in the production of 1 NADH and 2 ATP molecules.

5. **Conclusion**: Therefore, the final answer is that pyruvic acid is formed during glycolysis.