Answer :
A) Yeast eukaryotes use both aerobic respiration and fermentation based on oxygen availability .
Let's discuss the three main pathways of glucose catabolism: aerobic respiration, anaerobic respiration, and fermentation. For this discussion, I will focus on the yeast Saccharomyces cerevisiae, a eukaryote that uses both aerobic respiration and fermentation depending on oxygen availability.
Aerobic Respiration
Krebs cycle and electron transport system (ETS) are used.
Oxygen is the final electron acceptor.
Around 36-38 ATP molecules are produced per glucose molecule.
Fermentation
The Krebs cycle and ETS are not used.
An organic molecule, such as pyruvate or acetaldehyde, is the final electron acceptor.
Only 2 ATP molecules are produced per glucose molecule.
Comparatively, aerobic respiration is much more efficient at ATP production than fermentation, which highlights the role of oxygen in maximizing energy yield.