本题目来源于试卷: Form and Function B.3 Membranes & Membrane Transport，类别为 IB生物学
[单选题]
Some acetylcholine released by a mzeo+o/0xvk bl8 cp:b; otor neuron at the neurom)g zc.9j+fa(:rjodvouscular junction stimulates muscle contraction, while the remainder is rapidly.9 )og c(za dr+ojfvj: removed from the synapse. Which processes are required for this to happen?
A. Stimulation of contraction is receptor binding;Removal of excess acetylcholine is enzymatic degradation followed by reuptake of choline
B. Stimulation of contraction is endocytosis;Removal of excess acetylcholine is endocytosis followed by lysosomal degradation
C. Stimulation of contraction is receptor binding;Removal of excess acetylcholine is endocytosis followed by lysosomal degradation
D. Stimulation of contraction is endocytosis;Removal of excess acetylcholine is enzymatic degradation followed by reuptake of choline
参考答案: A
本题详细解析:
Acetylcholine is a neurotran //r; /,jvfs1eewq ifosmitter released by motor neurons at neuromuscular junctions. Once released, acetylcholine diffuses across the synaptic cleft to bind to receptors on the muscle cell. The binding ooqw/1s ,ierjfv /fe/;f acetylcholine to receptors initiates the depolarization of the muscle cell that leads to contraction. So, receptor binding is required for the stimulation of muscle contraction (Choice A and Choice C).The excess acetylcholine in the synaptic cleft needs to be removed to prevent overstimulation of the muscle. This removal happens through the hydrolysis of acetylcholine by the enzyme acetylcholinesterase to produce acetic acid and choline. The choline is taken up by the motor neuron so it may be used to make more acetylcholine. So, the removal of excess acetylcholine is achieved by enzymatic degradation followed by the reuptake of choline (Choice A).Choice B and Choice D are incorrect because endocytosis is not involved in muscle stimulation. Choice C is incorrect as acetylcholine is broken down before choline diffuses back across the synaptic cleft to be taken up and reused by the neuron.
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