Question

If the volume of \(\text{CO}_{2}\) evolved during respiration is less than the oxygen consumed, then the respiratory substrate would be ____.

• A. glucose
• B. fructose
• C. galactose
• D. fats

Hint:

RQ less than 1 means the substrate is poor in oxygen, such as fats.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept
Respiratory quotient (RQ) is the ratio of the volume of \(\text{CO}_{2}\) evolved to the volume of \(\text{O}_{2}\) consumed. Here it is less than 1.

Step 2: Carbohydrates
Glucose, fructose and galactose are carbohydrates with RQ equal to 1.

Step 3: Fats
Fats contain little oxygen relative to carbon and hydrogen, so they need more oxygen to oxidise. Tripalmitin gives an RQ of about 0.7.

Final Answer:
The respiratory substrate is fat. \[ \boxed{\text{(D) }\text{fats}} \]