Question

What is the respiratory quotient of organic acids?

Answer 1

The respiratory quotient (RQ), also known as the respiratory ratio (RQ), is defined as the volume of $CO_2$ released divided by the volume of oxygen absorbed during respiration. It is a dimensionless number used in the calculation of basal metabolic rate, which is calculated by estimating carbon dioxide production versus oxygen absorption.

Complete answer:
When estimating basal metabolic rate (BMR) from carbon dioxide production, the respiratory quotient (RQ or respiratory coefficient) is a dimensionless quantity. The ratio of carbon dioxide produced by the body to oxygen consumed by the body is used to calculate it. Such measurements, like oxygen uptake measurements, are examples of indirect calorimetry.
A respirometer is used to measure it. Because different energy pathways are used for fats, carbohydrates, and proteins, the respiratory quotient value indicates which macronutrients are being metabolised. The respiratory quotient for lipid metabolism is approximately 0.7, for proteins it is approximately 0.8, and for carbohydrates it is approximately 1.0. The majority of the time, however, energy consumption is a combination of fats and carbohydrates. A mixed diet has an approximate respiratory quotient of 0.8. Energy balance, circulating insulin, and insulin sensitivity are some of the other factors that may influence the respiratory quotient.

Organic acids have a Respiratory Quotient (R.Q.) greater than one, for example, malic acid has an R.Q. of 1.33 (> 1).

Note:
The respiratory quotient has practical applications in severe cases of chronic obstructive pulmonary disease, where patients expend a significant amount of energy on respiratory effort. By increasing the proportion of fat in the diet, the respiratory quotient is reduced, resulting in a relative decrease in $CO_2$ production. This minimises the amount of energy required on breathing by lowering the respiratory load to remove $CO_2$.