The value of RQ when the respiratory substance is poor in oxygen is

Options

A. Zero
B. Infinity
C. Greater than 1
D. Less than 1

Answer

To determine the value of the respiratory quotient (RQ) when the respiratory substance is poor in oxygen, we can follow these steps:

### Step-by-Step Solution:

1. **Understand 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. It is expressed as:
\[ RQ = \frac{\text{Volume of CO2 produced}}{\text{Volume of O2 consumed}} \]

2. **Identify the Respiratory Substances**: Different respiratory substances have different RQ values based on their chemical composition. Carbohydrates, fats, and proteins are common substrates. Carbohydrates generally have a higher oxygen content compared to fats.

3. **Analyze the Oxygen Content**: When a respiratory substance is poor in oxygen (like fats), it means that more oxygen is needed for its complete oxidation. For example, fats have a lower ratio of oxygen to carbon, which results in a lower RQ value.

4. **Example Calculation**: Consider the example of triolein (a fat), which has the chemical formula C57H104O6. The complete oxidation of triolein can be represented as:
\[ C57H104O6 + O2 \rightarrow CO2 + H2O \]
In this case, the oxidation of triolein produces 57 molecules of CO2 and requires 80 molecules of O2.

5. **Calculate RQ for Triolein**:
\[ RQ = \frac{57 \text{ (CO2 produced)}}{80 \text{ (O2 consumed)}} = 0.7 \]
This value is less than 1, indicating that the respiratory substance (triolein) is poor in oxygen.

6. **Conclusion**: Therefore, when the respiratory substance is poor in oxygen, the RQ value is typically less than 1.

### Final Answer:
The value of RQ when the respiratory substance is poor in oxygen is less than 1 (specifically, in the case of fats, it can be around 0.7).

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