When proteins are respiratory substrate, RQ will be

Options

A. 0.7
B. 1
C. 0.9
D. More than one

Answer

### Step-by-Step Solution:

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

2. **Identify the Respiratory Substrates**:
- Common respiratory substrates include carbohydrates, fats, and proteins.
- Each substrate has a characteristic RQ value:
- Carbohydrates typically have an RQ of 1.0.
- Fats have an RQ of approximately 0.7.
- Proteins have an RQ of approximately 0.9.

3. **Determine the RQ for Proteins**:
- Since the question specifies that proteins are the respiratory substrate, we need to refer to the known RQ value for proteins.
- The RQ value for proteins is approximately 0.9.

4. **Evaluate the Options**:
- If options are provided, we can analyze them:
- Option 1: 0.7 (This is the RQ for fats, so it's incorrect).
- Option 2: 1.0 (This is the RQ for carbohydrates, so it's incorrect).
- Option 3: 0.9 (This is the correct RQ for proteins).
- Option 4: More than 1 (No respiratory substrate has an RQ greater than 1, so it's incorrect).

5. **Conclusion**:
- The correct answer to the question "When proteins are respiratory substrate, RQ will be" is 0.9.

### Final Answer:
The RQ when proteins are the respiratory substrate is **0.9**.

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