Question 17N.2.HL.TZ0.c
| Date | November 2017 | Marks available | [Maximum mark: 8] | Reference code | 17N.2.HL.TZ0.c |
| Level | HL | Paper | 2 | Time zone | TZ0 |
| Command term | Explain | Question number | c | Adapted from | N/A |
Nitrogen is part of many important substances in living organisms.
Explain how insects excrete nitrogenous wastes.
[8]
a. excreted as uric acid
b. excretion by Malpighian tubules
c. nitrogenous waste/ammonia «accumulates» in hemolymph
d. nitrogenous waste/ammonia absorbed by Malpighian tubules
e. ammonia converted to uric acid
f. conversion to uric acid requires energy/ATP
g. high solute concentration in Malpighian tubules
OR
active transport of ions/Na+/K+ into Malpighian tubules
h. water absorbed by osmosis flushes uric acid/nitrogenous waste to «hind» gut
i. water/ions reabsorbed from the feces and returned to hemolymph
j. uric acid precipitates/becomes solid/forms a paste so can pass out with little water
k. uric acid excreted/egested with the feces
l. water conservation/osmoregulation
OR
reduces mass of water «in body»
m. uric acid is non-toxic
[Max 8 Marks]
