AP Bio multiple choice section unit 4
with solutions
Cell communication is critical for the function of both unicellular and multicellular eukaryotes.
Which of the following is likely true of cell signaling?
A
Cell signaling uses the highest molecular weight molecules found in living cells.
B
Cell signaling has largely been replaced by other cell functions in higher mammals.
C
Similar cell signaling pathways in diverse eukaryotes are evidence of conserved evolutionary
processes.
D
Cell signaling functions mainly during early developmental stages. - ANSWER c
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.
Previous experiments indicate that CDK5 is active only when attached to a protein called p35.
Which of the following best predicts how p35 might play a role in re - ANSWER b
Many human cells can be stimulated to divide by hormonelike growth factors that bind to
receptor proteins (R) on the plasma membrane and trigger an internal signal-transduction
,cascade. In many cases, however, the process of contact inhibition prevents mitosis when cells
are in direct contact with one another. Contact inhibition occurs when proteins called cell
adhesion molecules (CAMs) interact, causing them to change shape so that the growth-factor
signaling proteins that normally associate with CAMs are replaced by another protein, called M.
Both pathways are depicted in the figures below.
Which of the following statements accurately uses the information presented to support the
hypothesis that interruption of M function in a single body cell can result in cancer?
A
Protein 3 will be prevented from interacting withCAMs, causing the cell cycle to stop
permanently.
B
The ras protein will remain bound to DNA, block - ANSWER c
Cortisol is a hormone produced in response to stress, including starvation, in humans. Which of
the following is most likely an immediate effect of a starvation-induced increase in cortisol
secretion?
A
Increased activation of the immune system
B
Increased urine production by the kidneys
C
Increased bone and collagen formation
D
Increased mobilization of fatty acids from fat cells - ANSWER d
The diagram above shows a developing worm embryo at the four-cell stage. Experiments have
shown that when cell 3 divides, the anterior daughter cell gives rise to muscle and gonads and
, the posterior daughter cell gives rise to the intestine. However, if the cells of the embryo are
separated from one another early during the four-cell stage, no intestine will form. Other
experiments have shown that if cell 3 and cell 4 are recombined after the initial separation, the
posterior daughter cell of cell 3 will once again give rise to normal intestine. Which of the
following is the most plausible explanation for these findings?
A
A cell surface protein on cell 4 signals cell 3 to induce formation of the worm's intestine.
B
The plasma membrane of cell 4 interacts with the plasma membrane of the posterior portion of
cell 3, causing invaginations that become microvilli.
C
Cell 3 passes an electrical signal to cell 4, which in - ANSWER a
Epinephrine is a protein hormone found in many animals. Epinephrine stimulates a signaling
pathway that results in the breakdown of glycogen to glucose in the liver cells. Which of the
following describes the initial steps in the process whereby epinephrine stimulates glycogen
breakdown?
A
Epinephrine binds to a cell-surface receptor; the activated receptor stimulates production of the
second messenger, cAMP.
B
Epinephrine binds to a cell-surface receptor; the activated receptor catalyzes the conversion of
glycogen to glucose.
C
Epinephrine diffuses through the plasma membrane; the hormone dimerizes in the cytosol.
D
Epinephrine is taken into the cell by endocytosis; glycogen is converted to glucose in the
endocytotic vesicle. - ANSWER a
with solutions
Cell communication is critical for the function of both unicellular and multicellular eukaryotes.
Which of the following is likely true of cell signaling?
A
Cell signaling uses the highest molecular weight molecules found in living cells.
B
Cell signaling has largely been replaced by other cell functions in higher mammals.
C
Similar cell signaling pathways in diverse eukaryotes are evidence of conserved evolutionary
processes.
D
Cell signaling functions mainly during early developmental stages. - ANSWER c
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.
Previous experiments indicate that CDK5 is active only when attached to a protein called p35.
Which of the following best predicts how p35 might play a role in re - ANSWER b
Many human cells can be stimulated to divide by hormonelike growth factors that bind to
receptor proteins (R) on the plasma membrane and trigger an internal signal-transduction
,cascade. In many cases, however, the process of contact inhibition prevents mitosis when cells
are in direct contact with one another. Contact inhibition occurs when proteins called cell
adhesion molecules (CAMs) interact, causing them to change shape so that the growth-factor
signaling proteins that normally associate with CAMs are replaced by another protein, called M.
Both pathways are depicted in the figures below.
Which of the following statements accurately uses the information presented to support the
hypothesis that interruption of M function in a single body cell can result in cancer?
A
Protein 3 will be prevented from interacting withCAMs, causing the cell cycle to stop
permanently.
B
The ras protein will remain bound to DNA, block - ANSWER c
Cortisol is a hormone produced in response to stress, including starvation, in humans. Which of
the following is most likely an immediate effect of a starvation-induced increase in cortisol
secretion?
A
Increased activation of the immune system
B
Increased urine production by the kidneys
C
Increased bone and collagen formation
D
Increased mobilization of fatty acids from fat cells - ANSWER d
The diagram above shows a developing worm embryo at the four-cell stage. Experiments have
shown that when cell 3 divides, the anterior daughter cell gives rise to muscle and gonads and
, the posterior daughter cell gives rise to the intestine. However, if the cells of the embryo are
separated from one another early during the four-cell stage, no intestine will form. Other
experiments have shown that if cell 3 and cell 4 are recombined after the initial separation, the
posterior daughter cell of cell 3 will once again give rise to normal intestine. Which of the
following is the most plausible explanation for these findings?
A
A cell surface protein on cell 4 signals cell 3 to induce formation of the worm's intestine.
B
The plasma membrane of cell 4 interacts with the plasma membrane of the posterior portion of
cell 3, causing invaginations that become microvilli.
C
Cell 3 passes an electrical signal to cell 4, which in - ANSWER a
Epinephrine is a protein hormone found in many animals. Epinephrine stimulates a signaling
pathway that results in the breakdown of glycogen to glucose in the liver cells. Which of the
following describes the initial steps in the process whereby epinephrine stimulates glycogen
breakdown?
A
Epinephrine binds to a cell-surface receptor; the activated receptor stimulates production of the
second messenger, cAMP.
B
Epinephrine binds to a cell-surface receptor; the activated receptor catalyzes the conversion of
glycogen to glucose.
C
Epinephrine diffuses through the plasma membrane; the hormone dimerizes in the cytosol.
D
Epinephrine is taken into the cell by endocytosis; glycogen is converted to glucose in the
endocytotic vesicle. - ANSWER a
