Question

unit examinations content
page 13 of 51
question 12
the exchange of o₂ and co₂ in body cells is called:
a inhalation.
b metabolism.
c external respiration.
d internal respiration.
e catabolism.

Explanation:

• Option A: Inhalation is the process of taking air (with O₂) into the lungs, not cell - level gas exchange.
• Option B: Metabolism is the sum of all chemical reactions in the body, not specifically gas exchange.
• Option C: External respiration occurs between the lungs and the blood, not at the body cell level.
• Option D: Internal respiration is defined as the exchange of O₂ and CO₂ between the blood and body cells, which matches the description in the question.
• Option E: Catabolism is the breakdown of complex molecules in metabolism, not related to gas exchange.

Answer:

D. internal respiration.