At what percent of alcohol concentration does the Yeast poison itself to death ?

Options

A. 7
B. 9
C. 11
D. 13

Answer

To determine the percentage of alcohol concentration at which yeast poisons itself to death, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Yeast and Alcohol Production**:
- Yeast, specifically the strain *Saccharomyces cerevisiae*, is a unicellular fungus used for alcohol production through anaerobic respiration.
- During this process, glucose is converted into ethanol (alcohol) and carbon dioxide.

2. **Identify the Process of Alcohol Fermentation**:
- In anaerobic respiration, glucose is broken down into pyruvic acid through glycolysis.
- Pyruvic acid is then converted into ethanol and carbon dioxide during fermentation.

3. **Recognize the Toxicity of Ethanol**:
- Ethanol is a by-product of fermentation and is slightly acidic.
- As the concentration of ethanol increases, it becomes toxic to yeast cells.

4. **Determine the Toxic Concentration**:
- Research and studies indicate that yeast begins to experience toxic effects at around 13% alcohol concentration.
- Beyond this concentration, the environment becomes hostile, leading to the death of yeast cells.

5. **Conclusion**:
- The concentration at which yeast poisons itself to death is approximately **13%** alcohol.

### Final Answer:
The yeast poisons itself to death at **13% alcohol concentration**.

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