Question 21M.2.HL.TZ1.b
| Date | May 2021 | Marks available | [Maximum mark: 2] | Reference code | 21M.2.HL.TZ1.b |
| Level | HL | Paper | 2 | Time zone | TZ1 |
| Command term | Outline | Question number | b | Adapted from | N/A |
Outline the role of the sodium–potassium pump in maintaining the resting potential.
[2]
a. sodium/potassium pump pumps sodium ions Na+ out of axon and pumps potassium ions/K+ in ✔
b. requires energy/ATP/against concentration gradients/active transport ✔
c. three sodium ions pumped out for every two potassium ions pumped in ✔
d. results in charge difference between inside and outside where outside is positive relative to inside ✔
Strong students answered this question showing clear understanding of the process. However, most students showed poor understanding with errors: correct direction of ions being pumped not known; the direction of ions during repolarization was mixed up with resting state. Few wrote about the charge difference between inside and outside of the axon during the resting potential.
