A-LevelBiologyControl and coordination9700/41 · Oct/Nov 2020 · Q612 Marks

Identify the precise location in a cholinergic synapse that is described in each of the statements. A region that contains many mitochondria. A region where exocytosis of ACh occurs. A region that contains voltage-gated channel proteins. A region that contains ligand-gated channel proteins.

(a)(i)Identify the precise location in a cholinergic synapse that is described in each of the statements. A region that contains many mitochondria. A region where exocytosis of ACh occurs. A region that contains voltage-gated channel proteins. A region that contains ligand-gated channel proteins.[4]
(a)(ii)Outline the roles of synapses in the nervous system.[2]
(b)Some insecticides contain compounds called organophosphates. Organophosphates can act as enzyme inhibitors in neuromuscular junctions. People who use organophosphates and do not follow safety guidelines are at risk of organophosphate poisoning, which affects muscle function. Suggest how organophosphates could affect muscle function in humans.[4]
(c)Outline the role of the sarcoplasmic reticulum in the contraction of striated muscle.[2]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2020). The mark or mark type is shown in brackets.

[4] (a)(i) (cytoplasm of) presynaptic / terminal, knob ; presynaptic membrane ; presynaptic membrane ; postsynaptic membrane ;
[2] (a)(ii) any two from: one-way / unidirectional (transmission of impulses); communication between (many) neurones ; AVP;
[4] (b) any four from: 1 binds to / inhibits, acetylcholinesterase; 2 active site, blocked / shape changes; 3 Ach / acetylcholinesterase, not broken down / stays bound to receptors; 4 Na+ channels stay open ; 5 sarcolemma, (stays) depolarised / has constant action potentials ; 6 muscles stay contracted;
[2] (c) any two from: 1 Ca2+ channels open ; 2 Ca2+, diffuses / released, into sarcoplasm ; 3 Ca2+ binds to troponin ; 4 tropomyosin, moves / changes position ; 5 cross-bridges form / myosin binds to actin ;

On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.