Question

R.Q. is highest when respiratory substance is?

• A. Fat
• B. Malic acid
• C. Glucose
• D. Protein

Answer 1

The correct option is B Malic acid

Respiratory quotient is the ratio of the volume of carbon dioxide produced to the volume of oxygen consumed in respiration over a period of time. Its value can be one, zero, more than 1 or less than one.

RQ = Volume of C02 evolved/Volume of 02 absorbed

RQ slightly more than unity is found when organic acids are broken down as respiratory substrates under aerobic conditions, for e.g. oxalic acid, malic acid, succinic acid, etc.

C${}_4$H${}_6$O + 3O${}_2$ $\to$ 4CO${}_2$ + 3H${}_2$ RQ = 4 CO${}_2$/3 O${}_2$ or 1.3 malic acid

So the correct option is 'malic acid'.