R.Q. is maximum when respiratory substrate is

Options

A. Glucose
B. Fat
C. Protein
D. Malic acid.

Answer

To determine when the respiratory quotient (RQ) is maximum, we need to analyze the RQ values of different respiratory substrates. The RQ is defined as the volume of carbon dioxide produced divided by the volume of oxygen consumed during the oxidation of one mole of a substrate.

### Step-by-Step Solution:

1. **Understand RQ Values**:
- RQ is calculated using the formula:
\[ RQ = \frac{\text{Volume of CO}_2 \text{ produced}}{\text{Volume of O}_2 \text{ consumed}} \]

2. **Identify Common Respiratory Substrates**:
- Common substrates include glucose, fats, proteins, and organic acids.

3. **List RQ Values for Each Substrate**:
- Glucose: RQ = 1.0
- Fats: RQ = 0.7
- Proteins: RQ = 0.9
- Organic acids (e.g., malic acid): RQ > 1.0

4. **Examine Specific Organic Acids**:
- For malic acid, RQ = 1.33
- Other organic acids like oxalic acid have RQ = 4, and succinic acid has RQ = 1.41.

5. **Determine Maximum RQ**:
- Among the substrates listed, organic acids consistently have RQ values greater than 1. The highest value noted is for oxalic acid (RQ = 4).

6. **Conclusion**:
- The RQ is maximum when the respiratory substrate is an organic acid, specifically oxalic acid.

### Final Answer:
RQ is maximum when the respiratory substrate is oxalic acid.

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