DP Biology (last assessment 2024)

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Question 23M.3.HL.TZ2.9

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Date May 2023 Marks available [Maximum mark: 6] Reference code 23M.3.HL.TZ2.9
Level HL Paper 3 Time zone TZ2
Command term Explain Question number 9 Adapted from N/A
9.
[Maximum mark: 6]
23M.3.HL.TZ2.9

Explain how communication between neurons during synaptic transmission is achieved through neurotransmitters.

[6]

Markscheme
  1. neurotransmitters are (chemicals) released by exocytosis/vesicles (in the pre-synaptic neuron) after the arrival of a nerve impulse;
  2. neurotransmitters leave the presynaptic neuron;
  3. (neurotransmitters) attach to receptors in the postsynaptic neuron;
  4. neurotransmitters (in the synaptic cleft) are broken down/reabsorbed;
  5. fast-acting neurotransmitters attach to protein-ion channels (in postsynaptic membrane);
  6. slow-acting neurotransmitters activate second messengers (in postsynaptic membrane);
  7. slow-acting neurotransmitters affect more than one neuron;
  8. some neurotransmitters excite nerve impulses (in postsynaptic neuron) while others inhibit them;
  9. excitatory neurotransmitter causes generation of action potential;
  10. inhibitory neurotransmitter prevents threshold being reached (preventing action potential);
  11. summation of all excitatory / inhibitory neurotransmitters received in postsynaptic neuron;

Mp e and f: accept correct named example of fast-acting or slow-acting neurotransmitters.

Mp i and j: Accept correct named examples of excitatory/inhibitory neurotransmitters.

Examiners report

Most had a good knowledge of the basic mechanism of synaptic transmission, although it was sometimes difficult for some to use appropriate terminology, such as presynaptic and postsynaptic. Mentioning more elements such as fast- or slow-acting, excitatory or inhibitory neurotransmitters, and summation was more difficult for candidates.

Syllabus sections