In research on aging (both cellular aging and organismal aging), it has been found that aged cells do not progress through the cell cycle as they had previously. Which of the following would provide evidence that this is related to cell signaling?

In research on aging (both cellular aging and organismal aging), it has been found that aged cells do not progress through the cell cycle as they had previously. Which of the following would provide evidence that this is related to cell signaling?

A. cAMP levels change very frequently.
B. Their lower hormone concentrations elicit a lesser response.
C. ATP production decreases.
D. Enzymatic activity declines.
E. Growth factor ligands do not bind as efficiently to receptors.



Answer: E

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

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

A. excess skin loss
B. activation of a developmental pathway found in the worm but not in humans
C. formation of molecular pores in the mitochondrial outer membrane
D. neurodegeneration
E. a form of cancer in which there is insufficient apoptosis



Answer: E

Which of the following describes the events of apoptosis?

Which of the following describes the events of apoptosis?

A. The cell's DNA and organelles become fragmented, the cell dies, and it is phagocytized.
B. The cell dies, and the presence of its fragmented contents stimulates nearby cells to divide.
C. The cell's DNA and organelles become fragmented, the cell shrinks and forms blebs, and the cell's parts are packaged in vesicles that are digested by specialized cells.
D. The cell's nucleus and organelles are lysed, and the cell enlarges and bursts.
E. The cell dies, it is lysed, its organelles are phagocytized, and its contents are recycled.



Answer: C

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

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

A. Ced-9 remains inactive until it is signaled by ced-3 and other caspases.
B. Ced-9 cleaves to produce ced-3 and ced-4.
C. It prevents the caspase activity of ced-3 and ced-4.
D. Ced-9 prevents blebbing by its action on the cell membrane.
E. Ced-9 enters the nucleus and activates apoptotic genes.



Answer: C

Why is apoptosis potentially threatening to the healthy "neighbors" of a dying cell?

Why is apoptosis potentially threatening to the healthy "neighbors" of a dying cell?

A. Released cellular energy would interfere with the neighbors' energy budget.
B. Neighboring cells would activate immunological responses.
C. Cell death would usually spread from one cell to the next via paracrine signals.
D. Lysosomal enzymes exiting the dying cell would damage surrounding cells.
E. Bits of membrane from the dying cell could merge with neighbors and bring in foreign receptors.



Answer: D

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

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

A. The animal has as many genes as complex organisms, but finding those responsible is easier than in a more complex organism.
B. While the organism ages, its cells die progressively until the whole organism is dead.
C. All of its genes are constantly being expressed so all of its proteins are available from each cell.
D. The nematode undergoes a fixed and easy-to-visualize number of apoptotic events during its normal development.
E. This plant has a long-studied aging mechanism that has made understanding its death just a last stage.



Answer: D

What is apoptosis?

What is apoptosis?

A. a way to stimulate transcription
B. a type of second messenger
C. a type of membrane receptor
D. controlled cell suicide
E. a metabolic step in blood clotting


Answer: D

GTPase activity is important in the regulation of signal transduction because it

GTPase activity is important in the regulation of signal transduction because it

A. phosphorylates protein kinases.
B. converts cGMP to GTP.
C. hydrolyzes GTP to GDP thus shutting down the pathway.
D. decreases the amount of G protein in the membrane.
E. increases the available concentration of phosphate.



Answer: C

What are scaffolding proteins?

What are scaffolding proteins?

A. microtubular protein arrays that allow lipid-soluble hormones to get from the cell membrane to the nuclear pores
B. ladderlike proteins that allow receptor-ligand complexes to climb through cells from one position to another
C. large molecules to which several relay proteins attach to facilitate cascade effects
D. relay proteins that orient receptors and their ligands in appropriate directions to facilitate their complexing
E. proteins that can reach into the nucleus of a cell to affect transcription



Answer: C

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

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

A. Estrogen is produced in very large concentration and therefore diffuses widely.
B. Estrogen is kept away from the surface of any cells not able to bind it at the surface.
C. Estrogen has specific receptors inside several cell types, but each cell responds in the same way to its binding.
D. Estrogen binds to specific receptors inside many kinds of cells, each of which have different responses to its binding.
E. The subcomponents of estrogen, when metabolized, can influence cell response.



Answer: D

A drug designed to inhibit the response of cells to testosterone would almost certainly result in which of the following?

A drug designed to inhibit the response of cells to testosterone would almost certainly result in which of the following?

A. a decrease in G protein activity
B. an increase in receptor tyrosine kinase activity
C. an increase in cytosolic calcium concentration
D. a decrease in transcriptional activity of certain genes
E. lower cytoplasmic levels of cAMP



Answer: D

Why can a signaling molecule cause different responses in different cells?

Why can a signaling molecule cause different responses in different cells?

A. Different cells possess different enzymes, which modify the signaling molecule into different molecules after it has arrived.
B. Different cells have membrane receptors that bind to different sides of the signaling molecule.
C. The transduction process is unique to each cell type; to respond to a signal, different cells require only a similar membrane receptor.
D. The transduction pathway in cells has a variable length.
E. All of the above are correct.



Answer: C

Why are there often so many steps between the original signal event and the cell's response?

Why are there often so many steps between the original signal event and the cell's response?

A. Long, highly specific pathways minimize the possibility that a relay molecule accidentally could activate a pathway leading to a secondary response.
B. The accumulation of genetic mutations over time has added redundant steps to the pathway.
C. Each transduction is a checkpoint.
D. Lengthy pathways provide the opportunity for the initial pathway molecules to recycle back to inactive forms should additional signaling molecules be present.
E. Each step in a cascade produces a large number of activated products, causing signal amplification as the cascade progresses.



Answer: E

For the greatest advantage of multiple steps in a transduction pathway is:

For the greatest advantage of multiple steps in a transduction pathway is:

A. Each individual step can remove excess phosphate groups from the cytoplasm.
B. Having multiple steps provides for greater possible amplification of a signal.
C. Each step can be activated by several G proteins simultaneously.
D. Many of the steps can be used in multiple pathways.
E. Having multiple steps in a pathway requires the least amount of ATP.



Answer: B

Sutherland discovered that the signaling molecule epinephrine:

Sutherland discovered that the signaling molecule epinephrine:

A. elevates cytosolic concentrations of cyclic AMP.
B. interacts directly with glycogen phosphorylase.
C. causes lower blood glucose by binding to liver cells.
D. brings about a decrease in levels of cAMP as a result of bypassing the plasma membrane.
E. interacts with insulin inside muscle cells.


Answer: A

In which of the following ways could signal transduction most probably be explored in research to treat cancer?

In which of the following ways could signal transduction most probably be explored in research to treat cancer?

A. increase in the concentration of phosphodiesterases in order to produce more AMP
B. alteration of protein kinases in cell cycle regulation in order to slow cancer growth
C. removal of serine/threonine phosphate acceptors from transduction pathways in colon pre-cancerous growths
D. expansion of the role of transduction inhibitors in the cells before they give rise to cancer
E. increase in calcium ion uptake into the cytoplasm in order to modulate the effects of environmental carcinogens


Answer: B

Which of the following most likely would be an immediate result of growth factor binding to its receptor?

Which of the following most likely would be an immediate result of growth factor binding to its receptor?

A. phosphorylase activity
B. protein kinase activity
C. protein phosphatase activity
D. adenylyl cyclase activity
E. GTPase activity



Answer: B

In general, a signal transmitted via phosphorylation of a series of proteins

In general, a signal transmitted via phosphorylation of a series of proteins

A. allows target cells to change their shape and therefore their activity.
B. requires binding of a hormone to a cytosol receptor.
C. requires phosphorylase activity.
D. brings a conformational change to each protein.
E. cannot occur in yeasts because they lack protein phosphatases.


Answer: D

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

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

A. the hydrolysis of cGMP to GMP.
B. the removal of GMP from the cell.
C. the phosphorylation of GDP.
D. the dephosphorylation of cGMP.
E. the hydrolysis of GTP to GDP.



Answer: A

Which of the following would be inhibited by a drug that specifically blocks the addition of phosphate groups to proteins?

Which of the following would be inhibited by a drug that specifically blocks the addition of phosphate groups to proteins?

A. G protein-coupled receptor binding
B. ligand-gated ion channel signaling
C. receptor tyrosine kinase activity
D. adenylyl cyclase activity
E phosphatase activity



Answer: C