Which one of the following has the highest R.Q.

Options

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

Answer

To determine which substance has the highest respiratory quotient (R.Q.), we need to understand what R.Q. is and then analyze the given options.

### Step-by-Step Solution:

1. **Define Respiratory Quotient (R.Q.):**
- R.Q. is the ratio of the volume of carbon dioxide (CO2) produced to the volume of oxygen (O2) consumed during respiration.
- Mathematically, it is expressed as:
\[ R.Q. = \frac{\text{Volume of CO2 produced}}{\text{Volume of O2 consumed}} \]

2. **Understand the significance of R.Q.:**
- R.Q. provides information about the type of substrate being metabolized for energy. Different substrates yield different R.Q. values.

3. **Analyze the given options:**
- **Malic Acid:** The R.Q. for malic acid is approximately 1.33.
- **Protein:** The R.Q. for proteins typically ranges from 0.8 to 0.9.
- **Fat:** The R.Q. for fats is always less than 1.
- **Starch (Carbohydrate):** The R.Q. for starch is generally around 1.

4. **Compare the R.Q. values:**
- Malic Acid: 1.33
- Protein: 0.8 to 0.9
- Fat: Less than 1
- Starch: 1

5. **Determine the highest R.Q.:**
- Among the given options, malic acid has the highest R.Q. value of 1.33.

### Conclusion:
The substance with the highest respiratory quotient (R.Q.) among the options provided is **malic acid**.

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