Question 1

Cells that are infected, damaged, or have reached the end of their functional life span often undergo "programmed cell death". This controlled cell suicide is called "apoptosis". Select the appropriate description of this event on a cell's life cycle.

Accepted Answer

A)   Apoptosis is regulated by cell surface receptors that signal when a cell has reached its density-dependent limits.
B)   During apoptosis, dying cells leak out their contents, including digestive enzymes that also destroy healthy cells.
C)   During apoptosis, cellular agents chop up the DNA and fragment the organelles and other cytoplasmic components of a cell.
D)   Each cell organelle has protein signals that initiate the breakdown of the organelle's components, which leads to cell death. C

Question 2

If an adult person has a faulty version of the human analogue to ced-4 of the nematode, which of the following is most likely to result?

Accepted Answer

A)   Activation of a developmental pathway found in the worm but not in humans.
B)   A form of cancer in which there is insufficient apoptosis.
C)   Formation of molecular pores in the mitochondrial outer membrane.
D)   Excess skin loss will occur. B

Question 3

Protein kinase is an enzyme that functions in which of the following ways?

Accepted Answer

A)   as a second messenger molecule
B)   as a receptor for various signal molecules
C)   activates or inactivates other proteins by adding a phosphate group to them
D)   activates a G protein

Question 4

Caffeine is an inhibitor of phosphodiesterase. Therefore, the cells of a person who has recently consumed coffee would have increased levels of which of the following molecules?

Accepted Answer

A)   phosphorylated proteins
B)   cAMP
C)   adenylyl cyclase
D)   activated G proteins B

Question 5

When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?

Accepted Answer

A)   relay molecule
B)   transducer
C)   signal molecule
D)   response molecule

Question 6

If an animal cell suddenly lost the ability to produce GTP, what might happen to its signalling system?

Accepted Answer

A)   It would not be able to activate G proteins on the cytoplasmic side of the plasma membrane.
B)   It would be able to carry out reception and transduction but would not be able to respond to a signal.
C)   It would use ATP instead of GTP to activate G proteins on the cytoplasmic side of the plasma membrane.
D)   It would not be able to activate receptor tyrosine kinases.

Question 7

Viagra causes dilation of blood vessels and increased blood flow to the penis, facilitating erection. Viagra acts by inhibiting which of the following events?

Accepted Answer

A)   hydrolysis of cGMP to GMP
B)   hydrolysis of GTP to GDP
C)   dephosphorylation of cGMP
D)   formation of cGMP from GTP

Question 8

In the nematode C. elegans, ced-9 prevents apoptosis in a normal cell in which of the following ways?

Accepted Answer

A)   It prevents the caspase activity of ced-3 and ced-4.
B)   Ced-9 remains inactive until it is signalled by ced-3 and other caspases.
C)   Ced-9 cleaves to produce ced-3 and ced-4.
D)   Ced-9 prevents blebbing by its action on the cell membrane.

Question 9

- Which of the following types of signalling is represented in the figure?

Accepted Answer

A)   autocrine
B)   paracrine
C)   hormonal
D)   synaptic

Question 10

At puberty, an adolescent female body changes in both structure and function of several organ systems, primarily under the influence of changing concentrations of oestrogen and other steroid hormones. How can one hormone, such as oestrogen, mediate so many effects?

Accepted Answer

A)   Oestrogen is produced in very large concentration by nearly every tissue of the body.
B)   Each cell responds in the same way when steroids bind to the cell surface.
C)   Oestrogen is kept away from the surface of any cells, not able to bind it at the surface.
D)   Oestrogen binds to specific receptors inside many kinds of cells, each with different responses.

Question 11

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because they ________.

Accepted Answer

A)   are species-specific
B)   always lead to the same cellular response
C)   amplify the original signal many times
D)   counter the harmful effects of phosphatases

Question 12

Which of the following is true during a typical cAMP-mediated signal transduction event?

Accepted Answer

A)   The second messenger is the last part of the system to be activated.
B)   A hormone activates the second messenger by directly binding to it.
C)   The second messenger amplifies the hormonal response by attracting more hormones to the cell being affected.
D)   Adenylyl cyclase is activated after the hormone binds to the cell and before phosphorylation of proteins occurs.

Question 13

Sutherland discovered that the signalling molecule adrenaline is responsible for which of the following events?

Accepted Answer

A)   Stimulating glycogen synthesis.
B)   Decreasing blood glucose levels.
C)   Interacting directly with glycogen phosphorylase.
D)   Elevating cytosolic concentrations of cyclic AMP.

Question 14

Which observation suggested to Sutherland the involvement of a second messenger in adrenalineadrenaline's effect on liver cells?

Accepted Answer

A)   Enzymatic activity was proportional to the amount of calcium added to a cell-free extract.
B)   Receptor studies indicated that adrenaline adrenalinewas a ligand.
C)   Glycogen breakdown was observed only when adrenaline adrenalinewas administered to intact cells.
D)   Glycogen breakdown was observed only when adrenaline adrenalineand glycogen phosphorylase were mixed.

Question 15

Why has C. elegans proven to be a useful model for understanding apoptosis?

Accepted Answer

A)   C. elegans does not naturally use apoptosis, but can be induced to do so in the laboratory.
B)   C. elegans undergoes a fixed and easy-to-visualise number of apoptotic events during its normal development.
C)   C. elegans has large cells wherein apoptosis is easily observed without the aid of a microscope.
D)   As C. elegans ages, its cells die progressively until the whole organism is dead.

Question 16

If a pharmaceutical company wished to design a drug to maintain low blood sugar levels, one approach might be to design a compound that does which of the following?

Accepted Answer

A)   activates adrenaline receptors in liver cells
B)   increases cAMP production in liver cells
C)   blocks G protein activity in liver cells
D)   increases glycogen phosphorylase activity in liver cells

Question 17

Binding of a signalling molecule to which type of receptor leads directly to a change in the distribution of ions on opposite sides of the membrane?

Accepted Answer

A)   receptor tyrosine kinase
B)   G protein-coupled receptor
C)   ligand-gated ion channel
D)   steroid receptor

Question 18

What role do phosphatases play in signal transduction pathways?

Accepted Answer

A)   They transfer a phosphate group from one protein in the pathway to the next molecule in the series.
B)   They activate protein kinases by phosphorylation.
C)   They amplify the second messenger cAMP.
D)   They inactivate protein kinases to turn off signal transduction.

Question 19

A mutation that knocks out the GTPase activity of a G protein would have what effect on a cell?

Accepted Answer

A)   The concentration of available GTP would decrease.
B)   The number of G proteins in the cell would increase.
C)   The G protein would be inactivated by a G protein-coupled receptor/signal molecule complex.
D)   The G protein would always be active.

Question 20

Which of the following provides the best evidence that cell-signalling pathways evolved early in the history of life?

Accepted Answer

A)   Cell-signalling pathways are seen in "primitive" cells such as bacteria and yeast.
B)   Bacteria and yeast cells signal each other in a process called "quorum sensing".
C)   Signal transduction molecules identified in distantly related organisms are similar.
D)   Most signals in all types of cells are received by cell surface receptors.

Exam 11: Cell Communication

Cells that are infected, damaged, or have reached the end of their functional life span often undergo "programmed cell death". This controlled cell suicide is called "apoptosis". Select the appropriate description of this event on a cell's life cycle.

Correct AnswerverifiedC

If an adult person has a faulty version of the human analogue to ced-4 of the nematode, which of the following is most likely to result?

Correct AnswerverifiedB

Protein kinase is an enzyme that functions in which of the following ways?

Correct AnswerverifiedShow Answer

Caffeine is an inhibitor of phosphodiesterase. Therefore, the cells of a person who has recently consumed coffee would have increased levels of which of the following molecules?

Correct AnswerverifiedB

When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?

Correct AnswerverifiedShow Answer

If an animal cell suddenly lost the ability to produce GTP, what might happen to its signalling system?

Correct AnswerverifiedShow Answer

Viagra causes dilation of blood vessels and increased blood flow to the penis, facilitating erection. Viagra acts by inhibiting which of the following events?

Correct AnswerverifiedShow Answer

In the nematode C. elegans, ced-9 prevents apoptosis in a normal cell in which of the following ways?

Correct AnswerverifiedShow Answer

- Which of the following types of signalling is represented in the figure?

Correct AnswerverifiedShow Answer

At puberty, an adolescent female body changes in both structure and function of several organ systems, primarily under the influence of changing concentrations of oestrogen and other steroid hormones. How can one hormone, such as oestrogen, mediate so many effects?

Correct AnswerverifiedShow Answer

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because they ________.

Correct AnswerverifiedShow Answer

Which of the following is true during a typical cAMP-mediated signal transduction event?

Correct AnswerverifiedShow Answer

Sutherland discovered that the signalling molecule adrenaline is responsible for which of the following events?

Correct AnswerverifiedShow Answer

Which observation suggested to Sutherland the involvement of a second messenger in adrenalineadrenaline's effect on liver cells?

Correct AnswerverifiedShow Answer

Why has C. elegans proven to be a useful model for understanding apoptosis?

Correct AnswerverifiedShow Answer

If a pharmaceutical company wished to design a drug to maintain low blood sugar levels, one approach might be to design a compound that does which of the following?

Correct AnswerverifiedShow Answer

Binding of a signalling molecule to which type of receptor leads directly to a change in the distribution of ions on opposite sides of the membrane?

Correct AnswerverifiedShow Answer

What role do phosphatases play in signal transduction pathways?

Correct AnswerverifiedShow Answer

A mutation that knocks out the GTPase activity of a G protein would have what effect on a cell?

Correct AnswerverifiedShow Answer

Which of the following provides the best evidence that cell-signalling pathways evolved early in the history of life?

Correct AnswerverifiedShow Answer

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