AP Biology 4.2.A Signal Transduction Pathways

Practise AP Biology 4.2.A questions by identifying how protein modification can alter pathway components and connect signal reception to a response.

[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
describes the most likely mechanism by which
CDK5 regulates neurotransmitter release?

A

CDK5 adds methyl groups to DNA, altering
expression of genes required for synthesis
of neurotransmitters.

B

CDK5 promotes the rearrangement of the
lipid molecules of two bilayers into a single
membrane.

C

CDK5 alters the activity of other proteins
involved in the movement of synaptic
vesicles to the plasma membrane.

D

CDK5 binds to gated ion channels in the
postsynaptic membrane, resulting in
diffusion of calcium ions.

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4.2.A—Describe the components of a signal transduction pathway question 1