Question

Different substrates get oxidized during respiration. How does Respiratory Quotient ($RQ$) indicate which type of substrate, i.e., carbohydrate, fat or protein is getting oxidized?

$R.Q=A/B$

What do $A$ and $B$ stand for?

What type of substrates have $R.Q.of1,<1or>1?$

Answer 1

Respiratory quotient

Respiratory quotient is the ratio of volume of $C{O}_2$ evolved to the volume of $O_2$ consumed during respiration.

Value of respiratory quotient

The value of the respiratory quotient indicates which substance is being oxidized (respiratory substrate). Carbohydrates, proteins, fats all of them require different volumes of oxygen for their oxidation and evolve different volumes of carbon dioxide.

Respiratory Substrate	Respiratory Quotient (RQ)
Carbohydrates	1
Fats	> 1
Proteins	> 1
Organic acid	< 1

A and B

A stands for the volume of $C{O}_2$ evolved

B stands for the volume of $O_2$ consumed