Question

Define RQ. Write a short note on RQ.

Answer 1

Hint: Respiratory quotient is the ratio of carbon dioxide production to oxygen consumption. The value of RQ (respiratory quotient) depends upon the type of food substance that is metabolized.

Complete Answer:
- Respiratory quotient (RQ) is the ratio between the net output of carbon dioxide from tissues to the simultaneous net uptake of oxygen by the tissues. It is used to determine the utilization of different foodstuffs.
- For about 1 hour after meals, the respiratory quotient is 1.0. It is because usually, immediately after taking meals, only the carbohydrates are utilized by the tissues.
- During the metabolism of carbohydrates, one molecule of carbon dioxide is produced for every molecule of oxygen consumed by the tissues. That means during carbohydrate metabolism, the amount of carbon dioxide produced in the tissue is equal to the amount of oxygen consumed. Therefore, the Respiratory quotient is 1.0.
- If only fat is used for metabolism, the RQ is 0.7. When fat is utilized, oxygen reacts with fats and a large portion of oxygen combines with hydrogen ions to form water instead of carbon dioxide. So, the carbon dioxide output is less than the oxygen consumed. And the RQ is less. If only protein is utilized, R is 0.8.
- After the utilization of all the carbohydrates available, the body starts utilizing fats. Now the respiratory quotient becomes 0.7. When the proteins are metabolized, it becomes 0.8.

Note: During exercise, the respiratory quotient increases. The respiratory quotient in resting condition is 1.0 and during exercise, it increases to 1.5 to 2. As metabolism and exchange of respiratory gases are increased.