| Date | May 2016 | Marks available | 1 | Reference code | 16M.1.HL.TZ0.16 |
| Level | Higher level | Paper | Paper 1 | Time zone | TZ0 |
| Command term | Deduce | Question number | 16 | Adapted from | N/A |
Question
What is the mechanism of sodium-potassium pumps in neurons that generates a resting potential by active transport?
A. K+ from cytoplasm binds to the pump and stimulates its phosphorylation by ATP.
B. Phosphorylation of the pump causes its shape change in order to move Na+ into the cytoplasm.
C. K+ from inside the cell binds to the pump and causes the release of the phosphate group.
D. Na+ from cytoplasm binds to the pump and stimulates its phosphorylation by ATP.
Markscheme
D
Examiners report
Many teachers believed this question was beyond the scope of what is needed to be known about the sodium-potassium pump. Although the team agree with them; this question could be answered just by looking at the movement of ions, therefore it is acceptable.
