Question

after glycolysis, the pyruvate molecules can follow two different metabolic routes: aerobic and anaerobic respiration. what is the main difference between these?
a) anaerobic respiration does not need oxygen to occur and aerobic respiration does
b) aerobic respiration occurs in the presence of oxygen and anaerobic respiration is inhibited in its presence
c) anaerobic respiration does not occur in mammalian cells
d) they are the same metabolic pathway, occurring in different locations

Explanation:

• Option a: While oxygen requirement differs, this does not capture the full key distinction, as anaerobic respiration is actually inhibited by oxygen, not just independent of it.
• Option b: This correctly identifies the core difference: aerobic respiration relies on oxygen to proceed, and oxygen inhibits anaerobic respiration (the Pasteur effect), which is the defining contrast between the two pathways.
• Option c: Incorrect, as mammalian cells (e.g., muscle cells) perform anaerobic respiration during oxygen deprivation.
• Option d: Incorrect, as they are distinct metabolic pathways with different end products and energy yields.

Answer:

b) Aerobic respiration occurs in the presence of oxygen and anaerobic respiration is inhibited in its presence