AP Biology 2.5.B Large-Molecule Transport

Practise AP Biology 2.5.B questions by identifying how cells engulf particles and release vesicle contents through phagocytosis, endocytosis or exocytosis.

[Maximum number: 1]

Questions 43-48

Figure 1. Model of synapse

Researchers investigating the regulation of neurotransmitter release from presynaptic neurons proposed a model
(Figure 1) in which CDK5, a protein expressed in axon terminals, inhibits the movement of synaptic vesicles to the
presynaptic membrane.
To test their model, the researchers used a modified version of green fluorescent protein (GFP*). In slightly
alkaline conditions, GFP* exhibits a bright green fluorescence. In acidic conditions, GFP* exhibits no fluorescence.
Using standard techniques, the gene encoding GFP* is easily introduced into living cells. By engineering the
expression of GFP* in laboratory-cultured nerve cells, the researchers found that a bright green fluorescence was
exhibited only when a presynaptic neuron was given a certain stimulus.

Based on the model, which of the following best
explains why a bright green fluorescence was
observed following stimulation of a presynaptic
neuron?

A

GFP* synthesis was activated when a gene
taken up by the neuron was switched on.

B

GFP* stored in the cytoplasm of the neuron
was packaged into synaptic vesicles.

C

GFP* contained in synaptic vesicles moved
into the synaptic cleft by exocytosis.

D

GFP* present in the synaptic cleft was
reabsorbed by endocytosis into the neuron.

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2.5.B—Describe the mechanisms that organisms use to transport large molecules across the plasma membrane question 1