What is respiratory quotient (RQ)?

Respiratory quotient (RQ) is the ratio of the volume of carbon dioxide (CO₂) produced to the volume of oxygen (O₂) consumed during respiration. It is used to determine the type of substrate (carbohydrates, fats, or proteins) being metabolized for energy.

The formula for RQ is:

RQ = CO₂ produced / O₂ consumed

The value of RQ varies depending on the type of nutrient being respired:

• For carbohydrates, RQ is approximately 1.0, because the amount of CO₂ produced equals the amount of O₂ consumed.

• For fats, RQ is around 0.7, as more oxygen is required for oxidation compared to the carbon dioxide produced.

• For proteins, RQ is typically about 0.8.

RQ provides insight into metabolic activity and energy utilization in organisms. It is particularly useful in physiological studies, exercise science, and clinical settings to assess metabolic conditions.

In plants, RQ may vary depending on the type of stored food being used during respiration.

Overall, respiratory quotient is an important parameter for understanding the efficiency and nature of cellular respiration.