Question 22N.2.SL.TZ0.5
| Date | November 2022 | Marks available | [Maximum mark: 6] | Reference code | 22N.2.SL.TZ0.5 |
| Level | SL | Paper | 2 | Time zone | TZ0 |
| Command term | Explain, Identify, Outline | Question number | 5 | Adapted from | N/A |
The diagram shows the release of a neurotransmitter across a synapse.
[Source: Splettstoesser T., 2015. SynapseSchematic [diagram online] Available at :
https://commons.wikimedia.org/w/index.php?curid=41349083 [Accessed 14 January 2023].]
Identify the structure labelled X.
[1]
(Neurotransmitter) vesicle;
Do not accept Vacuole.
The majority managed to label X as a vesicle in (a). In (b) weaker candidates tried to explain the propagation of the action potential, rather than the release of the neurotransmitter. Better candidates were able to give almost textbook answers to explain the actions of the pesticide. Many got tangled up trying to explain, with those who had never seen this part of the syllabus, just saying that pesticides kill insects.
Outline how the neuron is stimulated to release the neurotransmitter.
[2]
- the arrival of a nerve impulse/action potential/depolarization (stimulates the release of a neurotransmitter);
- depolarization stimulates calcium ion channels to open;
OR
calcium ions enter the presynaptic knob/button - (calcium ions) cause the vesicle to fuse with / move to the membrane
OR
vesicles release neurotransmitter by exocytosis;
Explain the action of neonicotinoid pesticides in insects.
[3]
- prevents synaptic/nerve transmission
- is /acts like /has similar structure to a neurotransmitter/acetylcholine
- (neonicotinoid pesticides) bind to acetylcholine receptors in the post synaptic membrane;
- neonicotinoid pesticides are not broken down (as acetylcholine would be) by acetylcholinesterase/enzyme;
- the receptors are overstimulated
- paralyses/kills the insects;