Multiple Choice
When a vesicle fuses to the plasma membrane what happens to the lipids in the vesicles?
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13. Intracellular Protein Transport
Exocytosis
Multiple Choice
An axon terminal releases dopamine into the extracellular space primarily by which mechanism?
A
Passive diffusion of dopamine directly through the phospholipid bilayer
B
Transport through gap junction channels connecting the neuron to the extracellular space
C
Ca-triggered fusion of synaptic vesicles with the plasma membrane (exocytosis)
D
Engulfment of extracellular fluid containing dopamine followed by vesicle rupture (endocytosis)
Verified step by step guidance1
Understand that neurotransmitters like dopamine are stored in synaptic vesicles within the axon terminal before release.
Recognize that passive diffusion through the phospholipid bilayer is unlikely because dopamine is a charged molecule and cannot easily cross the hydrophobic membrane interior.
Know that gap junctions connect the cytoplasm of adjacent cells but do not provide a direct channel from the neuron to the extracellular space for neurotransmitter release.
Recall that the primary mechanism for neurotransmitter release is exocytosis, which is triggered by an influx of calcium ions (Ca^{2+}) into the axon terminal.
Summarize that Ca^{2+}-triggered fusion of synaptic vesicles with the plasma membrane allows dopamine to be released into the extracellular space efficiently.
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