MCAT Biology Question — Repolarization
- by
- May 30, 2018
- MCAT Question of the Day
- Reviewed By: Liz Flagge
The generation of an action potential within a cell is shown in the graph below. Which of the following statements is true of the membrane during repolarization at the indicated by the arrow?
A. The voltage-gated sodium channels close stopping the flow of sodium into the cell and the voltage-gated potassium channels open allowing the flow of potassium out of the cell.
B. The voltage-gated sodium channels close stopping the flow of sodium out of the cell and the voltage-gated potassium channels open allowing the flow of potassium into the cell.
C. The voltage-gated potassium channels close stopping the flow of potassium into the cell and the voltage-gated sodium channels open allowing the flow of sodium out of the cell.
D. The voltage-gated potassium channels close stopping the flow of potassium out of the cell and the voltage-gated sodium channels open allowing the flow of sodium into the cell.
Click for Explanation
This question asks the examinee to identify the cellular response during an action potential at the time of repolarization. The time preceding that indicated by the arrow corresponds to the depolarization of the cell. During depolarization, the voltage-gated sodium channels are open and sodium flows down its concentration gradient into the cell.
After the cell depolarizes, the cell reestablishes the negative resting membrane potential by closing the voltage-gated sodium channels preventing the flow of sodium into the cell, and opening the voltage-gated potassium channels allowing the flow of potassium down its concentration gradient and out of the cell. The flow of positively charged potassium ions during repolarization results in the net loss of positive ions within the cell, which in effect creates a negatively charged interior. Thus, choice A is the correct answer.
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 expert using the form below. No obligation, just expert advice.
Search the Blog
Free Consultation
Interested in our Online MCAT Course, One-on-One MCAT Tutoring or Med admissions packages? Set up a free consultation with one of our experienced Senior Student Advisors.
Schedule NowPopular Posts
-
MCAT Blog What's on the MCAT?
-
MCAT Blog How to Review MCAT Full Lengths

Free MCAT Practice Account
Need 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