Glycolysis is a process

Options

A. In which glucose is broken down into pyruvate.
B. in which glycogen is broken down into glucose.
C. which occurs in mitochondria.
D. that occurs next to Kreb.s cycle.

Explanation

**Step-by-Step Text Solution:**

1. **Understanding Glycolysis**: Glycolysis is a metabolic process that breaks down glucose into pyruvate. It is a crucial step in both aerobic and anaerobic respiration.

2. **Location of Glycolysis**: This process occurs in the cytoplasm of the cell, not in the mitochondria.

3. **Reactions Involved**: Glycolysis consists of ten reactions, which are divided into two phases:
- **Preparatory Phase**: The first five reactions where glucose is prepared for breakdown.
- **Payoff Phase**: The next five reactions where energy is produced.

4. **End Products of Glycolysis**: The end products of glycolysis are:
- 2 molecules of pyruvate (from one molecule of glucose)
- 2 molecules of ATP (energy currency of the cell)
- 2 molecules of NADH (electron carrier)

5. **Aerobic vs. Anaerobic Respiration**:
- If oxygen is present, pyruvate enters the Krebs cycle and then the electron transport chain.
- If oxygen is absent, pyruvate undergoes fermentation, producing ethanol and carbon dioxide.

6. **Evaluating the Options**:
- **Option A**: "Glycolysis is a process in which glucose is broken down into pyruvate." This is correct.
- **Option B**: "In which glycogen is broken down into glucose." This is incorrect; this process is called glycogenolysis.
- **Option C**: "Which occurs in mitochondria." This is incorrect; glycolysis occurs in the cytoplasm.
- **Option D**: "That occurs next to Krebs cycle." This is also incorrect; glycolysis occurs before the Krebs cycle.

7. **Conclusion**: The correct answer is **Option A**: Glycolysis is a process in which glucose is broken down into pyruvate.

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