MCAT Biology Question — Electron Transport Chain
- Nov 17, 2014
- MCAT Biology, MCAT Blog, MCAT Question of the Day
A certain molecule acts by binding to cytochrome oxidase A3, the final enzyme in the electron transport chain. Administration of a large dose of this substance to a human would likely:
A) Lead to death due to an inability of the cell to pass electrons to oxygen, thus stopping aerobic respiration and asphyxiating the cells.
B) Lead to death due to an inadequate supply of ADP to accept a phosphate group at the ATP synthase enzyme.
C) Have no effect as cells would switch which macronutrient they metabolize to circumvent the blocked biochemical pathway.
D) Increase the cell’s ATP production as negative feedback would cause the cell to up-regulate anaerobic pathways.
The electron transport chain works by taking high-energy electrons from molecules like NADH and passing them through a series of enzymes, ultimately ending with oxygen as the final electron acceptor. If this chain is blocked, aerobic respiration would cease, killing the cell. Eukaryotic cells in humans cannot survive using only anaerobic respiration. Thus (A) is the right answer. Several poisons work in the manner described, most notably cyanide.
B: ADP is produced when cells use up ATP to carry out cell functions. Blocking the electron transport chain would have no effect on ADP’s immediate availability.
C: As discussed above, this poison would kill the person.
D: As discussed above, this poison would kill the person.
Want more MCAT practice?
We’ve got options for every schedule and learning style!
From the best online MCAT course created by top instructors with 524+ MCAT scores to the most representative full-length practice exams and private tutoring, we can custom tailor your MCAT prep to your goals!
Not sure which option is right for you? Schedule a free MCAT consultation with an MCAT Advisor using the form below. No obligation, just expert advice.
Search the Blog
Free ConsultationSchedule Now
MCAT Blog How to Review MCAT Full-Lengths
Free MCAT Practice AccountNeed great MCAT practice?
Get the most representative MCAT practice possible when you sign up for our free MCAT Account, which includes a half-length diagnostic exam and one of our full-length MCAT practice exams.Learn More