3) Which of the following best pairs neuron structure with function? a.Voltage-g

Question

3) Which of the following best pairs neuron structure with function? a.Voltage-gated calcium channels - endocytosis b.Voltage-gated sodium channels-action potential repolarization phase c. Synaptobrevin - vesicle priming d.SNAP-25 clathrin recruitment 4) Listed below are individual events that occur during chemical synaptic transmission. 1. Diffusion of transmitter across the synaptic cleft 2. Arrival of an action potential in the presynaptic terminal 3. Vesicle fusion with plasma membrane 4. Opening of voltage-gated Ca2+ channels 5. Activation of presynaptic, calcium-sensitive proteins Which of the following is the correct temporal sequence of these events? a.1, 2; 3; 4; 5 b. 5; 4; 2; 3; 1 c. 2; 5; 4; 3; 1 d. 2; 4; 5; 3; 1 5) ACh receptors at the neuromuscular junction... a. consist of four subunits b. open in response to the binding of a single ACh molecule c. are anion-permeable d. none of the above

Explanation / Answer

3.c Synaptobrevin- vesicle priming

4. d. 2,4,5,3,1

2.Arrival of an action terminal in the presynaptic terminal

4.Opening of voltage gated Ca2+channels

5. Activation of presynaptic, calcium sensitive proteins

3. Vesicle fusion with plasma membrane.

1.Diffusion of transmitter actoss the synaptic cleft.

5.(d) none of the above.

Reason:

AChRs at the skeletal neuromuscular junction form heteropentamers composed of two , one , one , and one subunits. When a single ACh ligand binds to one of the subunits of the ACh receptor it induces a conformational change at the interface with the second AChR subunit. This conformational change results in the increased affinity of the second subunit for a second ACh ligand. AChRs therefore exhibit a sigmoidal dissociation curve due to this cooperative binding.In vertebrates, acetylcholine (Ach) and glutamate receptors are cation channels, whereas -aminobutyric acid (GABA) and glycine receptors are anion channels.

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