u

A

A

Using the yeast signal transduction pathways

D

What is most likely to happen to an animal's target cells that lack receptors for local regulators? A) They might compensate by receiving nutrients via a factor. B) They could develop normally in response to neurotransmitters instead. C) They could divide but never reach full size. D) They might not be able to multiply in response to growth factors from nearby cells. E) Hormones would not be able to interact with target cells.

A

Which of the following is a likely explanation of why natural selection favored the evolution of signals for sexual reproduction? A) Even in the simplest organisms

C

Which of the following is characterized by a cell releasing a signal molecule into the environment

C

In the formation of biofilms

D

In yeast signal transduction

B

In which of the following ways do plant hormones differ from hormones in animals? A) Plant hormones interact primarily with intracellular receptors. B) Plant hormones may travel in air or through vascular systems. C) Animal hormones are found in much greater concentration. D) Plant hormones are synthesized from two or more distinct molecules. E) Animal hormones are primarily for mating and embryonic development.

A

In an experiment to track the movement of growth factor molecules from secretion to the point of receptor binding in a particular species of mammal

D

When a neuron responds to a particular neurotransmitter by opening gated ion channels

A

Of the following

A

Which of the following is true for the signaling system in an animal cell that lacks the ability to produce GTP? A) It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane. B) It could activate only the epinephrine system. C) It would be able to carry out reception and transduction but would not be able to respond to a signal. D) It would use ATP instead of GTP to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane. E) It would employ a transduction pathway directly from an external messenger.

B

Testosterone functions inside a cell by A) acting as a signal receptor that activates tyrosine kinases. B) binding with a receptor protein that enters the nucleus and activates specific genes. C) acting as a steroid signal receptor that activates ion channel proteins. D) becoming a second messenger that inhibits adenylyl cyclase. E) coordinating a phosphorylation cascade that increases spermatogenesis.

D

Which of the following is true of transcription factors? A) They regulate the synthesis of DNA in response to a signal. B) They transcribe ATP into cAMP. C) They initiate the epinephrine response in animal cells. D) They control gene expression. E) They regulate the synthesis of lipids in the cytoplasm.

D

One of the major categories of receptors in the plasma membrane reacts by forming dimers

E

Because most receptors are membrane proteins

B

Since steroid receptors are located intracellularly

C

Receptor tyrosine kinases (RTKs) are found at high levels on various cancer cells. A protein

D

The receptors for a group of signaling molecules known as growth factors are often A) ligand-gated ion channels. B) G protein-coupled receptors. C) cyclic AMP. D) receptor tyrosine kinases. E) neurotransmitters.

A

In general

E

Sutherland discovered that epinephrine signals A) a decrease in levels of cAMP as a result of bypassing the plasma membrane. B) lower blood glucose by binding to liver cells. C) interactions with insulin inside muscle cells. D) interactions directly with glycogen phosphorylase. E) elevation of cytosolic concentrations of cyclic AMP.

C

Which of the following is the best explanation for the inability of a specific animal cell to reduce the Ca2⁺ concentration in its cytosol compared with the extracellular fluid? A) blockage of the synaptic signal B) loss of transcription factors C) insufficient ATP levels in the cytoplasm D) low oxygen concentration around the cell E) low levels of protein kinase in the cell

A

The toxin of Vibrio cholerae causes profuse diarrhea because it A) modifies a G protein involved in regulating salt and water secretion. B) decreases the cytosolic concentration of calcium ions

E

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 signaling B) ligand-gated ion channel signaling C) adenylyl cyclase activity D) phosphatase activity E) receptor tyrosine kinase activity

A

Which of the following most likely would be an immediate result of growth factor binding to its receptor? A) protein kinase activity B) adenylyl cyclase activity C) GTPase activity D) protein phosphatase activity E) phosphorylase activity

D

An inhibitor of phosphodiesterase activity would have which of the following effects? A) block the response of epinephrine B) decrease the amount of cAMP in the cytoplasm C) block the activation of G proteins in response to epinephrine binding to its receptor D) prolong the effect of epinephrine by maintaining elevated cAMP levels in the cytoplasm E) block the activation of protein kinase A

C

Adenylyl cyclase has the opposite effect of which of the following? A) protein kinase B) protein phosphatase C) phosphodiesterase D) phosphorylase E) GTPase

C

Caffeine is an inhibitor of phosphodiesterase. Therefore

C

If a pharmaceutical company wished to design a drug to maintain low blood sugar levels

D

If a pharmaceutical company wished to design a drug to maintain low blood sugar levels

D

An inhibitor of which of the following could be used to block the release of calcium from the endoplasmic reticulum? A) tyrosine kinases B) serine/threonine kinases C) phosphodiesterase D) phospholipase C E) adenylyl cyclase

E

Which of the following statements is true of signal molecules? A) When signal molecules first bind to receptor tyrosine kinases

C

Which of the following is a correct association? A) kinase activity and the addition of a tyrosine B) phosphodiesterase activity and the removal of phosphate groups C) GTPase activity and hydrolysis of GTP to GDP D) phosphorylase activity and the catabolism of glucose E) adenylyl cyclase activity and the conversion of cAMP to AMP

A

One inhibitor of cGMP is Viagra. It provides a signal that leads to dilation of blood vessels and increase of blood in the penis

C

Which of the following is the best explanation for the fact that most transduction pathways have multiple steps? A) Most of the steps were already in place because they are steps in other pathways. B) Multiple steps in a pathway require the least amount of ATP. C) Multiple steps provide for greater possible amplification of a signal. D) Each individual step can remove excess phosphate groups from the cytoplasm. E) Each step can be activated by several G proteins simultaneously.

C

Which of the following amino acids are most frequently phosphorylated by protein kinases in the cytoplasm during signal transduction? A) tyrosines B) glycine and histidine C) serine and threonine D) glycine and glutamic acid E) Any of the 20 amino acids are equally phosphorylated.

E

The function of phosphatases in signal transduction is best described as to A) move the phosphate group of the transduction pathway to the next molecule of a series. B) prevent a protein kinase from being reused when there is another extracellular signal. C) amplify the transduction signal so it affects multiple transducers. D) amplify the second messengers such as cAMP. E) inactivate protein kinases and turn off the signal transduction.

A

What explains the increased concentration of Ca⁺⁺ in the ER? A) Calcium ions are actively imported from the cytoplasm into the ER. B) Calcium concentration is kept low in the cytoplasm because of its high usage level. C) Calcium cannot enter the plasma membrane through ion channels. D) Calcium levels in the blood or other body fluids are extremely low. E) The Ca ions are recycled from other molecules in the ER.

B

In which of the following ways could signal transduction most probably be explored in research to treat cancer? A) removal of serine/threonine phosphate acceptors from transduction pathways in colon pre-cancerous growths B) alteration of protein kinases in cell cycle regulation in order to slow cancer growth C) increase in calcium ion uptake into the cytoplasm in order to modulate the effects of environmental carcinogens D) expansion of the role of transduction inhibitors in the cells before they give rise to cancer E) increase in the concentration of phosphodiesterases in order to produce more AMP

C

A drug designed to inhibit the response of cells to testosterone would almost certainly result in which of the following? A) lower cytoplasmic levels of cAMP B) an increase in receptor tyrosine kinase activity C) a decrease in transcriptional activity of certain genes D) an increase in cytosolic calcium concentration E) a decrease in G protein activity

D

At puberty

C

What are scaffolding proteins? A) ladderlike proteins that allow receptor-ligand complexes to climb through cells from one position to another B) microtubular protein arrays that allow lipid-soluble hormones to get from the cell membrane to the nuclear pores 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

D

The termination phase of cell signaling requires which of the following? A) removal of the receptor B) activation of a different set of relay molecules C) converting ATP to camp D) incompatibility of the binding of the signal molecule to the receptor E) apoptosis

C

GTPase activity is involved in the regulation of signal transduction because it A) increases the available concentration of phosphate. B) decreases the amount of G protein in the membrane. C) hydrolyzes GTP binding to G protein. D) converts cGMP to GTP. E) phosphorylates protein kinases.

B

Why has C. elegans proven to be a useful model for understanding apoptosis? A) The animal has as many genes as complex organisms

D

Which of the following describes the events of apoptosis? A) The cell dies

C

If an adult person has a faulty version of the human analog to ced-4 of the nematode

B

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

A

In C. elegans

A

In research on aging (both cellular aging and organismal aging)

E

Where do apoptotic signals come from? A) the nucleus only B) the ER only C) ligand binding only D) mitochondrial protein leakage only E) all of the above

C

The human population's life expectancy has increased significantly but seems to have an upper limit. Which of the following might be described as an ecological consequence of passing that upper limit by regulating cell death? A) an increase in the relative frequency of deaths from cancer B) an increased need for gerontologists and other professionals to care for the elderly C) an increase in the total population of humans on the planet D) a decrease in the ratio of younger to older members of the population E) a decrease in the birth rate

D

Which of the following types of signaling is represented in the figure? A) autocrine B) paracrine C) hormonal D) synaptic E) long distance

C

In the figure

B

A major group of G protein-coupled receptors contains seven transmembrane α helices. The amino end of the protein lies at the exterior of the plasma membrane. Loops of amino acids connect the helices either at the exterior face or on the cytosol face of the membrane. The loop on the cytosol side between helices 5 and 6 is usually substantially longer than the others.

Where would you expect to find the carboxyl end? A) at the exterior surface B) at the cytosol surface C) connected with the loop at H5 and H6 D) between the membrane layers

E

A major group of G protein-coupled receptors contains seven transmembrane α helices. The amino end of the protein lies at the exterior of the plasma membrane. Loops of amino acids connect the helices either at the exterior face or on the cytosol face of the membrane. The loop on the cytosol side between helices 5 and 6 is usually substantially longer than the others.

The coupled G protein most likely interacts with this receptor A) at the NH₃ end. B) at the COO- end. C) along the exterior margin. D) along the interior margin. E) at the loop between H5 and H6.

D

A major group of G protein-coupled receptors contains seven transmembrane α helices. The amino end of the protein lies at the exterior of the plasma membrane. Loops of amino acids connect the helices either at the exterior face or on the cytosol face of the membrane. The loop on the cytosol side between helices 5 and 6 is usually substantially longer than the others.

If you wish to design an experiment to block the G protein-coupled receptor interaction

B

Affinity chromatography is a method that can be used to purify cell-surface receptors

B

Affinity chromatography is a method that can be used to purify cell-surface receptors

A

Humans have receptors for two kinds of beta adrenergic compounds such as catecholamines to control cardiac muscle contractions. Some are beta 1 receptors that promote increased heart rate. Other drugs

C

Humans have receptors for two kinds of beta adrenergic compounds such as catecholamines to control cardiac muscle contractions. Some are beta 1 receptors that promote increased heart rate. Other drugs

D

Humans have receptors for two kinds of beta adrenergic compounds such as catecholamines to control cardiac muscle contractions. Some are beta 1 receptors that promote increased heart rate. Other drugs

C

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because A) they are species specific. B) they always lead to the same cellular response. C) they amplify the original signal manyfold. D) they counter the harmful effects of phosphatases. E) the number of molecules used is small and fixed.

D

Binding of a signaling molecule to which type of receptor leads directly to a change in the distribution of ions on opposite sides of the membrane? A) receptor tyrosine kinase B) G protein-coupled receptor C) phosphorylated receptor tyrosine kinase dimer D) ligand-gated ion channel E) intracellular receptor

A

The activation of receptor tyrosine kinases is characterized by A) dimerization and phosphorylation. B) dimerization and IP3 binding. C) a phosphorylation cascade. D) GTP hydrolysis. E) channel protein shape change.

B

Lipid-soluble signaling molecules

A

Consider this pathway: epinephrine → G protein-coupled receptor → G protein → adenylyl cyclase → cAMP. Identify the second messenger. A) cAMP B) G protein C) GTP D) adenylyl cyclase E) G protein-coupled receptor

D

Apoptosis involves all but which of the following? A) fragmentation of the DNA B) cell-signaling pathways C) activation of cellular enzymes D) lysis of the cell E) digestion of cellular contents by scavenger cells

C

Which observation suggested to Sutherland the involvement of a second messenger in epinephrine's effect on liver cells? A) Enzymatic activity was proportional to the amount of calcium added to a cell-free extract. B) Receptor studies indicated that epinephrine was a ligand. C) Glycogen breakdown was observed only when epinephrine was administered to intact cells. D) Glycogen breakdown was observed when epinephrine and glycogen phosphorylase were combined. E) Epinephrine was known to have different effects on different types of cells.

C

Protein phosphorylation is commonly involved with all of the following except A) regulation of transcription by extracellular signaling molecules. B) enzyme activation. C) activation of G protein-coupled receptors. D) activation of receptor tyrosine kinases. E) activation of protein kinase molecules.