Which of the following is used as a cellular respiration indicator

Options

A. Tetrazolium chloride
B. Ethanol
C. Schiff s reagent
D. Lactic acid.

Answer

To determine which substance is used as a cellular respiration indicator, we can analyze the options provided:

1. **Tetrazolium Chloride**: This compound is a redox indicator that is specifically used to detect cellular respiration. It is reduced by the electron transport chain in mitochondria, particularly by complex I, and under anaerobic conditions, it is converted into an insoluble red compound known as 1,3,5-triphenylformazan. This property makes it an effective indicator for cellular respiration.

2. **Ethanol**: Ethanol is a product of alcoholic fermentation, which occurs in the absence of oxygen. While it is related to respiration, it is not an indicator of the process itself.

3. **Schiff's Reagent**: This reagent is used in organic chemistry to test for the presence of aldehydes and ketones. It is not related to cellular respiration.

4. **Lactic Acid**: Lactic acid is produced during anaerobic respiration in certain organisms, particularly in muscle cells during intense exercise. However, like ethanol, it is not an indicator of the respiration process.

Based on this analysis, the correct answer is **Tetrazolium Chloride**.

### Step-by-Step Solution:
1. **Identify the options**: The options given are tetrazolium chloride, ethanol, Schiff's reagent, and lactic acid.
2. **Analyze Tetrazolium Chloride**: Recognize that it is a redox indicator used to detect cellular respiration.
3. **Consider Ethanol**: Understand that ethanol is a byproduct of fermentation, not an indicator of respiration.
4. **Evaluate Schiff's Reagent**: Note that this reagent tests for aldehydes and ketones, unrelated to respiration.
5. **Look at Lactic Acid**: Acknowledge that lactic acid is produced during anaerobic respiration but does not serve as an indicator.
6. **Conclude**: Determine that the only substance that serves as a cellular respiration indicator is tetrazolium chloride.

### Final Answer:
The correct option is **Tetrazolium Chloride**.