Cellular respiration Question

[shefv]

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If a disorder affects the ability of the ETC to donate electrons to oxygen, the compound most likely to increase in someone is:

A Lactic Acid
B Phospholipids
C Alanine
D CO2

I was able to cross off B and C. I thought that if ETC can't give electrons to oxygen, then the amount of ATP made decreases however, since oxygen is still present, the cellular respiration process would still continue up until the TCA and so CO2 increases. Would the TCA not happen because of the build up of NADH and the process would revert to glycolysis/fermentation even though oxygen is still present?

The correct answer is A

 

[SkyJumper42]

NADH would revert to fermentation because the electrons on NADH can not be passed on by the ETC, so Pyruvate takes them turning into Lactic Acid. CO2 is generated in the TCA which can't happen because the electrons on NADH go to Pyruvate, rendering it unasable in the Citric Acid Cycle. No CO2 is produced in glycolysis, it is only produced during the Citric Acid Cycle.

 

[edgerock24]

NADH would revert to fermentation because the electrons on NADH can not be passed on by the ETC, so Pyruvate takes them turning into Lactic Acid. CO2 is generated in the TCA which can't happen because the electrons on NADH go to Pyruvate, rendering it unasable in the Citric Acid Cycle. No CO2 is produced in glycolysis, it is only produced during the Citric Acid Cycle.

Exactly.
The basic/non-bio major way that I would approach this question: basically, it's asking...."what will increase if oxygen is not present?" Although the Krebs Cycle doesn't directly need O2 to move forward, it is essentially useless without O2 being present. So, we can cut this question down to "what will increase under anaerobic conditions?" This leads us to Fermentation occurring -> increase in Lactic Acid.