Respiration in Plants - Respiratory quotient

The Respiratory Quotient ($RQ$) is defined as the ratio of the volume of $CO_2$ evolved to the volume of $O_2$ consumed during respiration over a specific period of time.

The value of $RQ$ depends entirely on the type of respiratory substrate being oxidized in the cell.

For Carbohydrates (e.g., Glucose), the $RQ$ is $1.0$ because the amount of $CO_2$ evolved is equal to the amount of $O_2$ consumed during complete oxidation.

For Fats (e.g., Tripalmitin), the $RQ$ is less than $1.0$ (typically around $0.7$) because fats are oxygen-poor and require more external $O_2$ for oxidation.

For Proteins, the $RQ$ value is approximately $0.9$.

For Organic Acids (e.g., Malic acid), the $RQ$ is greater than $1.0$ because these compounds are relatively oxygen-rich.

In Anaerobic Respiration, since $O_2$ is not consumed, the $RQ$ is considered to be infinity ($\infty$).