Which process must occur before fermentation?

Options

A. A) Krebs cycle
B. B) Glycolysis
C. C) Electron transport system
D. D) The transition reaction

Explanation

To determine which process must occur before fermentation, we can analyze the options provided:

1. **Understanding Fermentation**: Fermentation is a type of anaerobic respiration that occurs in the absence of oxygen. It allows cells to generate energy by breaking down organic food.

2. **Identifying the Processes**:
- **Option A: Krebs Cycle**: This process occurs in aerobic respiration and requires oxygen. It does not occur before fermentation.
- **Option B: Glycolysis**: This is the first step in both aerobic and anaerobic respiration. It breaks down glucose into pyruvate, which can then enter fermentation if oxygen is not present.
- **Option C: Electron Transport System**: This process is part of aerobic respiration and also requires oxygen, so it does not occur before fermentation.
- **Option D: Transition Reaction**: This process converts pyruvate into acetyl-CoA and occurs before the Krebs Cycle, but it is not necessary for fermentation.

3. **Conclusion**: The only process that must occur before fermentation is glycolysis, as it provides the necessary pyruvate for fermentation to take place.

**Final Answer**: The process that must occur before fermentation is **Option B: Glycolysis**.

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