Question 22N.2.HL.TZ0.5
| Date | November 2022 | Marks available | [Maximum mark: 7] | Reference code | 22N.2.HL.TZ0.5 |
| Level | HL | Paper | 2 | Time zone | TZ0 |
| Command term | Explain, Identify, Outline, State | Question number | 5 | Adapted from | N/A |
The diagram shows a nephron from a mammal.
[Source: Brody, T., 1999. The nephron. [diagram online] Available at:
https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/nephron [Accessed 29 October 2021].]
Identify structure X.
[1]
proximal convoluted tubule/PCT;
60null% of candidates identified the proximal convoluted tubule.
Identify structure Y.
[1]
glomerulus/Bowman’s capsule;
80% of candidates identified the structure as the glomerulus or Bowman's capsule.
State the region of the kidney in which the loop of Henle is situated.
[1]
medulla;
70% of candidates knew that the loop of Henle is in the medulla.
Explain the role of the hormone ADH in osmoregulation.
[2]
- ADH secreted if blood is hypertonic/solute concentration too high/water content too low/dehydrated;
- aquaporins open/more aquaporins in (plasma membranes of cells in DCT/collecting duct) with ADH;
- DCT/collecting duct becomes more permeable to water/reabsorbs more water (from filtrate);
This was generally well answered. A few candidates thought that ADH could both increase and decrease water reabsorption in the nephron. The commonest omission was hypertonic conditions being the signal that results in ADH secretion.
Outline two adaptations for water conservation in leaves of desert plants.
[2]
Mark the first two answers only
(thick) wax layer/cuticle;
hairs on leaves/rolled leaves;
sunken stomata/stomata in pits/stomata opening at night/CAM physiology;
(leaves reduced to) spines/needles/no/few/small leaves/low surface area (to volume ratio) of leaves;
thick stems/water storage tissue/vertical stems (to avoid most intense sunlight);
A wide range of leaf adaptations were suggested and most candidates gave one or two that were accepted. Root adaptations were not accepted as the question asked for features of leaves.