Question

The value of R.Q. for proteins is:
A.Equal to one
B.More than one
C.Less than one
D.Infinite

Answer 1

During aerobic respiration, oxygen is consumed and carbon dioxide is released. The ratio of the volume of carbon dioxide evolved to the volume of oxygen consumed during aerobic respiration is known as the respiratory quotient (R.Q) or as the respiratory ratio.

Complete step by step answer:
-The respiratory quotient depends upon the type of substrate oxidized during aerobic respiration.
-Proteins are catabolized into amino acids. Glucogenic amino acids such as alanine, asparagine, aspartic acid, glutamic acid, cysteine, glycine, etc. Are converted to various substrates of the glucogenic pathway to get oxidized further and form energy precursors. Ketogenic amino acids like leucine and lysine are converted to ketone bodies (acetone, acetoacetate, and beta-amino butyric acid) to form energy.
The respiratory quotient (RQ) ranges between 0.7-0.9. it can be calculated by the following formula:
RQ = Volume of carbon dioxide evolved (mL) / Volume of oxygen consumed (mL)

Hence option C is correct.

Note:
When carbohydrates are used as a substrate for aerobic respiration and are completely oxidized, the respiratory quotient (RQ) will be 1. This is because equal amounts of carbon dioxide are evolved and oxygen is consumed respectively.
When fats are used as a substrate for aerobic respiration, the RQ is less than 1.
Fats are converted to free fatty acids (FFA) and triglycerides (TAG). They can be converted to acetyl-CoA. This enters the glucogenic pathway to form energy precursors like NADH and FADH.
For example, in the case of groundnuts, that store fats are used as a respiratory substrate. The value of R.Q will be less than one.