A person at rest consumes (250\,\text{mL}\) of O$_2$ per minute and produces (200\,\text{mL}\) of CO$_2$ per minute. During moderate exercise the O$_2$ consumption rises to (1.2\,\text{L}\) per minute and CO$_2$ production to (1.0\,\text{L}\) per minute.

(a) Calculate the respiratory quotient (RQ) at rest and during exercise.
(b) By how much does the RQ change when the person starts exercising?
(c) Given that the RQ for pure carbohydrate metabolism is 1.0 and for pure fat metabolism is 0.7, what does the change in RQ suggest about the predominant substrate being used during exercise?

Question

A person at rest consumes (250\,\text{mL}\) of O$_2$ per minute and produces (200\,\text{mL}\) of CO$_2$ per minute. During moderate exercise the O$_2$ consumption rises to (1.2\,\text{L}\) per minute and CO$_2$ production to (1.0\,\text{L}\) per minute.

(a) Calculate the respiratory quotient (RQ) at rest and during exercise.
(b) By how much does the RQ change when the person starts exercising?
(c) Given that the RQ for pure carbohydrate metabolism is 1.0 and for pure fat metabolism is 0.7, what does the change in RQ suggest about the predominant substrate being used during exercise?

Accepted Answer

Rest RQ = 0.80; Exercise RQ = 0.83; the RQ increases by 0.03, indicating a shift toward greater carbohydrate utilisation during exercise.

Igcse Model Questions Vol1 2020 Biology Question 1

Answer Options

About This Question

Master the Exam!