Question 22M.1.SL.TZ1.29
| Date | May 2022 | Marks available | [Maximum mark: 1] | Reference code | 22M.1.SL.TZ1.29 |
| Level | SL | Paper | 1 | Time zone | TZ1 |
| Command term | Question number | 29 | Adapted from | N/A |
Leptin helps to regulate body mass in humans and mice. The image shows an obese mouse (O) and a normal mouse (N).
[Source: [Obesity in mice]. [image online] Available at: https://commons.wikimedia.org/wiki/File:Fatmouse.jpg Oak Ridge National Laboratory, U.S. Department of Energy.]
What hypothesis could account for the differences between the mice?
A. The hypothalamus of mouse O stopped producing leptin.
B. Adipose cells of mouse O are continuously producing leptin.
C. Mouse N has a defective leptin receptor.
D. Leptin binds to receptors in the hypothalamus of mouse N.
[1]
D
Here was yet another question that proved too difficult for many candidates, with the percentage answering correctly at no better than if based on guess-work. Most candidates thought that obesity in mice is caused by the hypothalamus stopping producing leptin. This reveals two misunderstandings — that the brain rather than adipose cells produces leptin and that obesity is due to a lack of the hormone rather than receptors failing to respond to it.
