Which of these is not true of fermentation?

Options

A. Net gain of only two ATP
B. Occurs in cytosol
C. NADH donates electrons to electron transport system
D. Begins with glucose

Explanation

To determine which statement is not true of fermentation, let's analyze the process of fermentation step by step:

### Step 1: Understanding Fermentation
Fermentation is a metabolic process that occurs in the absence of oxygen (anaerobic conditions). It follows glycolysis, where glucose is broken down into pyruvic acid.

**Hint:** Remember that fermentation occurs when oxygen is not available.

### Step 2: Glycolysis and Pyruvic Acid
During glycolysis, glucose is converted into pyruvic acid, producing a small amount of ATP and NADH in the process.

**Hint:** Glycolysis is the first step in both aerobic and anaerobic respiration.

### Step 3: The Role of NADH
In fermentation, the pyruvic acid produced from glycolysis is converted into either lactic acid (in lactic acid fermentation) or ethanol and carbon dioxide (in alcoholic fermentation). During this process, NADH is oxidized back to NAD+, allowing glycolysis to continue.

**Hint:** NADH must be recycled back to NAD+ for glycolysis to proceed in anaerobic conditions.

### Step 4: Electron Transport Chain (ETC)
In aerobic respiration, NADH donates electrons to the electron transport chain (ETC) in the mitochondria, which requires oxygen. However, in fermentation, since there is no oxygen, NADH does not participate in the ETC.

**Hint:** The electron transport chain is not involved in fermentation.

### Step 5: Identifying the False Statement
Given the options related to fermentation, the statement that "NADH donates electrons to the electron transport chain" is not true. This is because fermentation occurs in the absence of oxygen, and thus NADH does not enter the ETC.

**Hint:** Look for statements that contradict the anaerobic nature of fermentation.

### Conclusion
The correct answer to the question "Which of these is not true of fermentation?" is that NADH donates electrons to the electron transport chain.

### Summary of Steps:
1. Understand fermentation as an anaerobic process.
2. Recognize the role of glycolysis in producing pyruvic acid.
3. Identify the recycling of NADH during fermentation.
4. Note that the electron transport chain is not involved in fermentation.
5. Determine the false statement regarding NADH's role in fermentation.