Question 20N.2.HL.TZ0.7c
| Date | November 2020 | Marks available | [Maximum mark: 8] | Reference code | 20N.2.HL.TZ0.7c |
| Level | HL | Paper | 2 | Time zone | TZ0 |
| Command term | Explain | Question number | c | Adapted from | N/A |
Explain the role of the kidney in osmoregulation.
[8]
a. osmoregulation is regulation of water and solute/salt balance/solute concentrations;
b. nephron (is the functional unit of the kidney/osmoregulates);
c. ultrafiltration in glomerulus / glomerular filtrate collected by Bowman’s capsule;
d. loop of Henle establishes/maintains hypertonic conditions in medulla;
e. osmosis/reabsorption of water (from filtrate) in the collecting duct;
f. brain/hypothalamus monitors blood solute concentration / pituitary secretes ADH;
g. ADH secreted when solute concentration of blood is too high/hypertonic/when dehydrated;
h. ADH increases permeability of collecting duct to water;
i. ADH causes more aquaporins (in membranes of collecting duct wall cells);
j. more water reabsorbed resulting in more concentrated/hypertonic urine/less volume of urine;
k. less/no ADH secreted when solute concentration (of blood) is too low/hypotonic;
l. less water reabsorbed resulting in dilute/hypotonic urine/large volume of urine;
Reject ‘water balance’ and ‘water concentration’ for mpa.
There was some excellent knowledge of kidney function, frequently going way beyond the question’s requirements. In some cases, candidates just described all processes occurring in the kidney instead of actually answering the question. This generally led to the loss of the extra clarity mark.
