Aerobic respiration produces more usable chemical energy than fermentation, because fermentation involves

Options

A. formation of lactic acid
B. complete oxidation of food
C. partial oxidation of food
D. evolution of `CO_2` and alcohol

Answer

To solve the question, we need to understand the differences between aerobic respiration and fermentation, particularly in terms of energy production.

### Step-by-Step Solution:

1. **Understand Aerobic Respiration**:
- Aerobic respiration occurs in the presence of oxygen. It involves the complete oxidation of glucose (or other organic molecules) to produce carbon dioxide, water, and energy in the form of ATP (adenosine triphosphate).
- The overall reaction can be summarized as:
\[ \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{Energy (ATP)} \]
- This process yields a high amount of energy, approximately 36-38 ATP molecules per molecule of glucose.

2. **Understand Fermentation**:
- Fermentation is an anaerobic process, meaning it occurs in the absence of oxygen. It involves the partial oxidation of glucose.
- The products of fermentation can vary; for example, in alcoholic fermentation, ethanol and carbon dioxide are produced, while in lactic acid fermentation, lactic acid is produced.
- The overall reaction for alcoholic fermentation can be summarized as:
\[ \text{C}_6\text{H}_{12}\text{O}_6 \rightarrow 2\text{C}_2\text{H}_5\text{OH} + 2\text{CO}_2 + \text{Energy (ATP)} \]
- Fermentation typically yields only about 2 ATP molecules per molecule of glucose.

3. **Compare Energy Yield**:
- The key difference in energy yield between aerobic respiration and fermentation is due to the completeness of the oxidation process.
- Aerobic respiration fully oxidizes glucose, resulting in a higher energy yield (36-38 ATP), while fermentation only partially oxidizes glucose, resulting in a much lower energy yield (2 ATP).

4. **Conclusion**:
- Therefore, the reason aerobic respiration produces more usable chemical energy than fermentation is that fermentation involves the **partial oxidation of food**, leading to less energy production.

### Final Answer:
The correct answer is **C. Partial oxidation of food**.