How much of the energy of a glucose molecule is released in anaerobic respiration ending with fermentation?

Options

A. Around 15%
B. 0.02
C. Less than 7%
D. 7.6 k.cal

Answer

To determine how much energy of a glucose molecule is released in anaerobic respiration ending with fermentation, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Anaerobic Respiration**: Anaerobic respiration occurs in the absence of oxygen and results in the partial breakdown of glucose. The main types of anaerobic respiration include alcoholic fermentation and lactic acid fermentation.

2. **Energy Yield from Glucose**: In aerobic respiration, a glucose molecule can yield up to 36-38 ATP molecules, which is approximately 100% of its energy. However, in anaerobic respiration, the energy yield is significantly lower.

3. **Fermentation Process**: During fermentation, only glycolysis occurs, which takes place in the cytoplasm. Glycolysis breaks down one glucose molecule into two molecules of pyruvate, producing a net gain of 2 ATP molecules.

4. **Percentage of Energy Released**: The total energy available from one glucose molecule is equivalent to about 686 kilocalories (kcal). Since glycolysis yields only 2 ATP (which is about 7.3 kcal per ATP), the total energy released during fermentation is approximately 14.6 kcal.

5. **Calculate the Percentage**: To find the percentage of energy released during fermentation:
\[ \text{Percentage of energy released} = \left(\frac{\text{Energy released during fermentation}}{\text{Total energy in glucose}}\right) \times 100 \]
\[ = \left(\frac{14.6 \text{ kcal}}{686 \text{ kcal}}\right) \times 100 \approx 2.13\% \]

6. **Conclusion**: Since the energy released during fermentation is less than 7%, we can conclude that the correct answer to the question is **less than 7%**.

### Final Answer:
The energy released from a glucose molecule in anaerobic respiration ending with fermentation is **less than 7%**.

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