R.Q. of respiratory substrate `C_(39)H_(72)O_(6)` would be

Options

A. 0.718
B. 1.34
C. 2.71
D. 3.25

Answer

To find the respiratory quotient (RQ) of the respiratory substrate \( C_{39}H_{72}O_{6} \), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Type of Compound**:
- The molecular formula \( C_{39}H_{72}O_{6} \) suggests that it is a long-chain fatty acid. This is because fatty acids typically have a high carbon and hydrogen content with fewer oxygen atoms.

2. **Understand the Concept of RQ**:
- The respiratory quotient (RQ) is defined as the ratio of the volume of carbon dioxide (CO2) produced to the volume of oxygen (O2) consumed during respiration. The formula is:
\[ RQ = \frac{\text{Volume of } CO_2 \text{ produced}}{\text{Volume of } O_2 \text{ consumed}} \]

3. **Know the RQ Value for Fatty Acids**:
- It is a known fact that the RQ value for fatty acids is approximately 0.7. This is because the oxidation of fatty acids typically results in less CO2 being produced compared to the amount of O2 consumed.

4. **Evaluate the Given Options**:
- The options provided are:
- A) 0.718
- B) 1.34
- C) 2.71
- D) 3.25
- Since we know that the RQ for fatty acids is around 0.7, we can conclude that option A (0.718) is the closest to this value.

5. **Eliminate Incorrect Options**:
- Options B (1.34), C (2.71), and D (3.25) are too high for a fatty acid and are typically associated with organic acids, which can have RQ values greater than 1. Thus, they can be eliminated.

6. **Final Conclusion**:
- Therefore, the RQ of the respiratory substrate \( C_{39}H_{72}O_{6} \) is approximately 0.718.

### Final Answer:
The RQ of respiratory substrate \( C_{39}H_{72}O_{6} \) is **0.718**.