Question

The respiratory quotient of protein-carbohydrate and fat substrates are in the order:

• A. 0.7, 1, -1
• B. 0.9, 1, less than 1
• C. 0, -1, 1
• D. 1, 0.9, less than 1

Answer 1

The correct option is B

0.9, 1, less than 1

The correct option is B.

Explanation of the correct option:

1. A substrate's respiratory quotient (RQ) is defined as the ratio of the volume of ${\mathrm{CO}}_2$ generated to the volume of ${\mathrm{O}}_2$ consumed.
2. It is also affected by the kind of respiratory substrate.
3. Because of the full oxidation, the RQ for carbohydrate substrate is 1.
4. It is a directly proportional measure of the substrate's energy.
5. RQ is less than one when fats are utilized.
6. The RQ ratio for protein substrate would be 0.9.

Explanation of the incorrect options:

Option A:

1. The RQ of protein is 0.8-0.9.
2. Carbohydrate has a respiratory quotient of 1.
3. The RQ of fat is lower than 1 but never negative.

Option C:

1. The RQ of protein is 0.8-0.9 but never be 0.
2. Carbohydrate has a respiratory quotient of 1 but is never negative.
3. The RQ of fat will always be lower than 1 not greater than 1.

Option D:

1. Protein has a respiratory quotient of 0.8-0.9 but never be 1.
2. Carbohydrate has a respiratory quotient of 1, not less than 1.
3. Fat has a respiratory quotient of less than 1.

Final answer: The respiratory quotient of protein-carbohydrate and fat substrates are in the order 0.9, 1, less than 1.