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 1: Understand Yeast and Its Metabolism
Yeast, specifically the strain Saccharomyces cerevisiae, is a unicellular fungus that undergoes anaerobic respiration. During this process, it converts glucose into ethanol and carbon dioxide.

**Hint:** Remember that yeast performs anaerobic respiration, which leads to alcohol production.

### Step 2: Identify the Process of Alcohol Production
In the absence of oxygen, yeast converts pyruvic acid (produced from glycolysis) into ethanol and carbon dioxide. This process is known as alcoholic fermentation.

**Hint:** Focus on the conversion of pyruvic acid to ethanol as a key step in yeast metabolism.

### Step 3: Recognize the Toxicity of Ethanol
While yeast can produce ethanol, it can only tolerate a certain concentration of it. Beyond a specific threshold, ethanol becomes toxic to yeast cells.

**Hint:** Think about how many organisms can only tolerate certain levels of their own waste products.

### Step 4: Determine the Toxic Concentration
Research and studies indicate that the concentration of alcohol (ethanol) becomes harmful to yeast at around 13%. At this concentration, the yeast cells begin to die due to the toxicity of the ethanol.

**Hint:** Consider the safe limits of alcohol concentration for yeast and how exceeding these limits affects their survival.

### Conclusion
Thus, the percentage of alcohol concentration at which yeast poisons itself to death is **13%**.

**Final Answer:** D - 13%