In mitochondrial electron transport, what is the direct role of O2

Question

?
View Available Hint(s)for Part A

to provide the driving force for the synthesis of ATP
from ADP
and Pi

to function as the final electron acceptor in the electron transport chain
to provide the driving force for the production of a proton gradient
to oxidize NADH
and FADH2
from glycolysis, acetyl CoA formation, and the citric acid cycle
Part B - The effects of anaerobic conditions
How would anaerobic conditions (when no O2
is present) affect the rate of electron transport and ATP
production during oxidative phosphorylation? (Note that you should not consider the effect on ATP
synthesis in glycolysis or the citric acid cycle.)
View Available Hint(s)for Part B

Neither electron transport nor ATP
synthesis would be affected.
Electron transport would stop but ATP
synthesis would be unaffected.
Electron transport would be unaffected but ATP
synthesis would stop.
Both electron transport and ATP
synthesis would stop.
Part C - Comparing the amount of ATP synthesis from NADH and FADH2
NADH
and FADH2
are both electron carriers that donate their electrons to the electron transport chain. The electrons ultimately reduce O2
to water in the final step of electron transport. However, the amount of ATP
made by electrons from an NADH
molecule is greater than the amount made by electrons from an FADH2
molecule.
Which statement best explains why more ATP
is made per molecule of NADH
than per molecule of FADH2
?
View Available Hint(s)for Part C

It takes more energy to make ATP
from ADP
and Pi
using FADH2
than using NADH
.
FADH2
is made only in the citric acid cycle while NADH
is made in glycolysis, acetyl CoA formation, and the citric acid cycle.
There is more NADH
than FADH2
made for every glucose that enters cellular respiration.
Fewer protons are pumped across the inner mitochondrial membrane when FADH2
is the electron donor than when NADH
is the electron donor.
The H+
gradient made from electron transport using NADH
is located in a different part of the mitochondrion than the H+
gradient made using FADH2
.

Answer 1

Part A - Role of O2 in Mitochondrial Electron Transport

The direct role of O₂ in mitochondrial electron transport is:

to function as the final electron acceptor in the electron transport chain.

Part B - Effects of Anaerobic Conditions

Under anaerobic conditions (when no O₂ is present):

Both electron transport and ATP synthesis would stop.

The absence of O₂ means that there is no final electron acceptor for the electron transport chain, which halts the process and stops ATP production via oxidative phosphorylation.

Part C - ATP Synthesis from NADH vs. FADH2

The statement that best explains why more ATP is made per molecule of NADH than per molecule of FADH2 is:

Fewer protons are pumped across the inner mitochondrial membrane when FADH2 is the electron donor than when NADH is the electron donor.

This is because NADH donates electrons to a higher point in the electron transport chain than FADH2, resulting in a greater proton gradient and thus more ATP production.