Question

Protein is used as a respiratory substrate only when

• A. Carbohydrates are absent.
• B. Fats are absent.
• C. Both A and B are absent.
• D. Fats and carbohydrates are abundant.

Answer 1

The correct option is C Both A and B are absent.

Carbohydrates are the fuel of choice for cellular respiration. In case enough carbohydrates are not available, other biomolecules like fats and proteins can be used to supply for cellular energy requirements. Fats are burnt first when enough carbohydrates are not available. Proteins are used only when both carbohydrates and fats are not available.