Chapter 11: Cell Communication

Front 1

1) In the yeast signal transduction pathway, after both types of mating cells have released the mating factors and
the factors have bound to specific receptors on the correct cells,
A) binding induces changes in the cells that lead to cell fusion.
B) the cells then produce the a factor and the α factor.
C) one cell nucleus binds the mating factors and produces a new nucleus in the opposite cell.
D) the cell membranes fall apart, releasing the mating factors that lead to new yeast cells.
E) a growth factor is secreted that stimulates mitosis in both cells.

Back 1

A) binding induces changes in the cells that lead to cell fusion

Front 2

2) Which of the following is true of the mating signal transduction pathway in yeast?
A) The pathway carries an electrical signal between mating cell types.
B) Mating type a secretes a signal called a factor.
C) The molecular details of the pathway in yeast and in animals are very different.
D) Scientists think the pathway evolved long after multicellular creatures appeared on Earth.
E) The signal reception, transduction, and response occur in the nucleus.

Back 2

B) Mating type a secretes a signal called a factor.

Front 3

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

Back 3

D) They would not be able to multiply in response to growth factors from nearby cells

Front 4

4) Paracrine signaling
A) involves secreting cells acting on nearby target cells by discharging a local regulator into the extracellular
fluid.
B) requires nerve cells to release a neurotransmitter into the synapse.
C) occurs only in paracrine yeast cells.
D) has been found in plants but not animals.
E) involves mating factors attaching to target cells and causing production of new paracrine cells.

Back 4

A) involves secreting cells acting on nearby target cells by discharging a local regulator into the extracellular
fluid.

Front 5

5) From the perspective of the cell receiving the message, the three stages of cell signaling are
A) the paracrine, local, and synaptic stages.
B) signal reception, signal transduction, and cellular response.
C) signal reception, nucleus disintegration, and new cell generation.
D) the alpha, beta, and gamma stages.
E) signal reception, cellular response, and cell division.

Back 5

B) signal reception, signal transduction, and cellular response.

Front 6

6) The process of transduction usually begins
A) when the chemical signal is released from the alpha cell.
B) when the signal molecule changes the receptor protein in some way.
C) after the target cell divides.
D) after the third stage of cell signaling is completed.
E) when the hormone is released from the gland into the blood

Back 6

B) when the signal molecule changes the receptor protein in some way

Front 7

7) When a cell releases a signal molecule into the environment and a number of cells in the immediate vicinity
respond, this type of signaling is
A) typical of hormones.
B) autocrine signaling.
C) paracrine signaling.
D) endocrine signaling.
E) synaptic signaling.

Back 7

C) paracrine signaling

Front 8

8) Synaptic signaling between adjacent neurons is like hormone signaling in which of the following ways?
A) It sends its signal molecules through the blood.
B) It sends its signal molecules quite a distance.
C) It requires calcium ions.
D) It requires binding of a signaling molecule to a receptor.
E) It persists over a long period

Back 8

D) It requires binding of a signaling molecule to a receptor

Front 9

9) A small molecule that specifically binds to another molecule, usually a larger one
A) is called a signal transducer.
B) is called a ligand.
C) is called a polymer.
D) seldom is involved in hormonal signaling.
E) usually terminates a signal reception.

Back 9

B) is called a ligand

Front 10

10) Which of the following is (are) true of ligand-gated ion channels?
A) They are important in the nervous system.
B) They lead to changes in sodium and calcium concentrations in cells.
C) They open or close in response to a chemical signal.
D) Only A and B are true.
E) A, B, and C are true.

Back 10

E) A, B, and C are true.

Front 11

11) Of the following, a receptor protein in a membrane that recognizes a chemical signal is most similar to
A) the active site of an allosteric enzyme in the cytoplasm that binds to a specific substrate.
B) RNA specifying the amino acids in a polypeptide.
C) a particular metabolic pathway operating within a specific organelle.
D) an enzyme with an optimum pH and temperature for activity.
E) genes making up a chromosome.

Back 11

A) the active site of an allosteric enzyme in the cytoplasm that binds to a specific substrate

Front 12

12) What would be 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) Only A and C are true.
E) A, B, and C are true

Back 12

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

Front 13

13) G proteins and G-protein-linked receptors
A) are found only in animal cells, and only embedded in or located just beneath the cellʹs membrane.
B) are found only in bacterial cells, embedded in the cellʹs plasma membrane only.
C) are thought to have evolved very early, because of their similar structure and function in a wide variety of
modern organisms.
D) probably evolved from an adaptation of the citric acid cycle.
E) are not widespread in nature and were unimportant in the evolution of eukaryotes.

Back 13

C) are thought to have evolved very early, because of their similar structure and function in a wide variety of
modern organisms

Front 14

14) Membrane receptors that attach phosphates to specific animo acids in proteins are
A) not found in humans.
B) called receptor tyrosine-kinases.
C) a class of GTP G-protein signal receptors.
D) associated with several bacterial diseases in humans.
E) important in yeast mating factors that contain amino acids.

Back 14

B) called receptor tyrosine-kinases.

Front 15

15) Up to 60% of all medicines used today exert their effects by influencing what structures in the cell membrane?
A) tyrosine-kinases receptors
B) ligand-gated ion channel receptors
C) growth factors
D) G proteins
E) cholesterol

Back 15

D) G proteins

Front 16

16) Which of the following are chemical messengers that pass through the plasma membrane of cells and have
receptor molecules in the cytoplasm?
A) insulin
B) testosterone
C) cAMP
D) epinephrine

Back 16

C) cAMP

Front 17

17) Testosterone functions inside a cell by
A) acting as a signal receptor that activates ion-channel proteins.
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 glycogen metabolism

Back 17

B) binding with a receptor protein that enters the nucleus and activates specific genes

Front 18

18) Which is true of transcription factors?
A) They regulate the synthesis of DNA in response to a signal.
B) Some transcribe ATP into cAMP.
C) They initiate the epinephrine response in animal cells.
D) They control which genes are expressed.
E) They are needed to regulate the synthesis of lipids in the cytoplasm.

Back 18

D) They control which genes are expressed.

Front 19

19) Chemical signal pathways
A) operate in animals, but not in plants.
B) are absent in bacteria, but are plentiful in yeast.
C) involve the release of hormones into the blood.
D) often involve the binding of signal molecules to a protein on the surface of a target cell.
E) use hydrophilic molecules to activate enzymes

Back 19

D) often involve the binding of signal molecules to a protein on the surface of a target cell.

Front 20

20) 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

Back 20

B) at the cytosol surface

Front 21

21) 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

Back 21

E) at the loop between H5 and H6

Front 22

22) When an excess of the ligand (hormone) is poured through the column after the receptor binding step, what do
you expect will occur?
A) The ligand will attach to those beads that have the receptor and remain on the column.
B) The ligand will cause the receptor to be displaced from the beads and eluted out.
C) The ligand will attach to the bead instead of the receptor.
D) The ligand will cause the bead to lose its affinity by changing shape.
E) The reaction will cause a pH change due to electron transfer.

Back 22

B) The ligand will cause the receptor to be displaced from the beads and eluted out

Front 23

23) This method of affinity chromatography would be expected to collect which of the following?
A) molecules of the hormone
B) molecules of purified receptor
C) G proteins
D) assorted membrane proteins
E) hormone-receptor complexes

Back 23

B) molecules of purified receptor

Front 24

24) One of the major categories of receptors in the plasma membrane reacts by forming dimmers, adding
phosphate groups, then activating relay proteins. Which type does this?
A) G protein-linked receptor
B) ligand-gated ion channels
C) steroid receptors
D) receptor tyrosine kinases

Back 24

D) receptor tyrosine kinases

Front 25

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

Back 25

D) receptor tyrosine kinases.

Front 26

26) In general, a signal transmitted via phosphorylation of a series of proteins
A) brings a conformational change to each protein.
B) requires binding of a hormone to a cytosol receptor.
C) cannot occur in yeasts because they lack protein phosphatases.
D) requires phosphorylase activity.
E) allows target cells to change their shape and therefore their activity.

Back 26

A) brings a conformational change to each protein.

Front 27

27) Sutherland discovered that epinephrine
A) signals bypass the plasma membrane of cells.
B) lowers blood glucose by binding to liver cells.
C) interacts with insulin inside muscle cells.
D) interacts directly with glycogen phosphorylase.
E) elevates the cytosolic concentration of cyclic AMP.

Back 27

E) elevates the cytosolic concentration of cyclic AMP

Front 28

28) Which of the following is the best explanation for the inability of an 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

Back 28

C) insufficient ATP levels in the cytoplasm

Front 29

29) The general name for an enzyme that transfers phosphate groups from ATP to a protein is
A) phosphorylase.
B) phosphatase.
C) protein kinase.
D) ATPase.
E) protease

Back 29

C) protein kinase

Front 30

30) Which of the following describes cell communication systems?
A) Cell signaling evolved more recently than systems such as the immune system of vertebrates.
B) Communicating cells are usually close together.
C) Most signal receptors are bound to the outer membrane of the nuclear envelope.
D) Lipid phosphorylation is a major mechanism of signal transduction.
E) In response to a signal, the cell may alter activities by changes in cytosol activity or in transcription of
RNA.

Back 30

E) In response to a signal, the cell may alter activities by changes in cytosol activity or in transcription of
RNA.

Front 31

31) 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, making the cells hypotonic to the intestinal cells.
C) binds with adenylyl cyclase and triggers the formation of cAMP.
D) signals inositol trisphosphate to become a second messenger for the release of calcium.
E) modifies calmodulin and activates a cascade of protein kinases

Back 31

A) modifies a G protein involved in regulating salt and water secretion.

Front 32

32) Which of the following would be inhibited by a drug that specifically blocks the addition of phosphate groups
to proteins?
A) G-protein-linked receptor signaling
B) ligand-gated ion channel signaling
C) adenylyl cyclase activity
D) phosphatase activity
E) receptor tyrosine kinase activity

Back 32

E) receptor tyrosine kinase activity

Front 33

33) 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

Back 33

A) protein kinase activity

Front 34

34) 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

Back 34

D) prolong the effect of epinephrine by maintaining elevated cAMP levels in the cytoplasm

Front 35

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

Back 35

C) phosphodiesterase

Front 36

36) Caffeine is an inhibitor of phosphodiesterase. Therefore, the cells of a person who has recently consumed coffee
would have increased levels of
A) phosphorylated proteins.
B) GTP.
C) cAMP.
D) adenylyl cyclase.
E) activated G proteins.

Back 36

C) cAMP.

Front 37

37) If a pharmaceutical company wished to design a drug to maintain low blood sugar levels, one approach might
be to
A) design a compound that blocks epinephrine receptor activation.
B) design a compound that inhibits cAMP production in liver cells.
C) design a compound to block G-protein activity in liver cells.
D) design a compound that inhibits phosphorylase activity.
E) All of the above are possible approaches

Back 37

E) All of the above are possible approaches

Front 38

38) If a pharmaceutical company wished to design a drug to maintain low blood sugar levels, one approach might
be to
A) design a compound that mimics epinephrine and can bind to the epinephrine receptor.
B) design a compound that stimulates cAMP production in liver cells.
C) design a compound to stimulate G protein activity in liver cells.
D) design a compound that increases phosphodiesterase activity.
E) All of the above are possible approaches

Back 38

D) design a compound that increases phosphodiesterase activity

Front 39

39) 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

Back 39

D) phospholipase C

Front 40

40) Which of the following statements is true?
A) When signal molecules first bind to receptor tyrosine kinases, the receptors phosphorylate a number of
nearby molecules.
B) In response to some G-protein-mediated signals, a special type of lipid molecule associated with the
plasma membrane is cleaved to form IP3 and calcium.
C) In most cases, signal molecules interact with the cell at the plasma membrane and then enter the cell and
eventually the nucleus.
D) Toxins such as those that cause botulism and cholera interfere with the ability of activated G proteins to
hydrolyze GTP to GDP, resulting in phosphodiesterase activity in the absence of an appropriate signal
molecule.
E) Protein kinase A activation is one possible result of signal molecules binding to G protein-linked
receptors.

Back 40

E) Protein kinase A activation is one possible result of signal molecules binding to G protein-linked
receptors.

Front 41

41) 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

Back 41

C) GTPase activity and hydrolysis of GTP to GDP

Front 42

42) One inhibitor of cGMP is Viagra. It provides a signal that leads to dilation of blood vessels and increase of
blood in the penis, facilitating erection. cGMP is inhibited, therefore the signal is prolonged. The original signal
that is now inhibited would have
A) hydrolyzed cGMP to GMP.
B) hydrolyzed GTP to GDP.
C) phosphorylated GDP.
D) dephosphorylated cGMP.
E) removed GMP from the cell

Back 42

A) hydrolyzed cGMP to GMP

Front 43

43) 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

Back 43

C) a decrease in transcriptional activity of certain genes

Front 44

44) Which of the substances below is a protein that can hold several other relay proteins as it binds to an activated
membrane receptor?
A) active transcription factor
B) third messenger
C) ligand
D) scaffolding protein
E) protein kinase

Back 44

D) scaffolding protein

Front 45

46) The use of beta 2 antagonist drugs may be useful in asthma because
A) they may increase constriction of the skeletal muscle of the chest wall.
B) they may increase heart rate and therefore allow the patient to get more oxygen circulated.
C) they may dilate the bronchioles by relaxing their smooth muscle.
D) they may override the beta blockers that the patient is already taking.
E) they may obstruct all G protein-mediated receptors

Back 45

C) they may dilate the bronchioles by relaxing their smooth muscle

Front 46

47) 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 has specific receptors inside several cell types, but each cell responds in the same way to its
binding.
C) Estrogen is kept away from the surface of any cells not able to bind it at the surface.
D) Estrogen binds to specific receptors inside many kinds of cells, each of which have different responses to
its binding.
E) Estrogen has different shaped receptors for each of several cell types.

Back 46

D) Estrogen binds to specific receptors inside many kinds of cells, each of which have different responses to
its binding.

Front 47

48) What are scaffolding proteins?
A) ladder-like 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

Back 47

C) large molecules to which several relay proteins attach to facilitate cascade effects

Front 48

49) 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) reversing the binding of signal molecule to the receptor
E) apoptosis

Back 48

D) reversing the binding of signal molecule to the receptor

Front 49

51) Which of the following describes the events of apoptosis?
A) The cell dies, it is lysed, its organelles are phagocytized, its contents are recycled.
B) Its DNA and organelles become fragmented, it dies, and it is phagocytized.
C) The cell dies and the presence of its fragmented contents stimulates nearby cells to divide.
D) Its DNA and organelles are fragmented, the cell shrinks and forms blebs, and the cell self -digests.
E) Its nucleus and organelles are lysed, the cell enlarges and bursts.

Back 49

D) Its DNA and organelles are fragmented, the cell shrinks and forms blebs, and the cell self -digests

Front 50

52) The main proteases involved in apoptosis are
A) ced-3 and ced-4.
B) inactive.
C) cytochromes.
D) caspases.
E) G proteins.

Back 50

D) caspases.

Front 51

53) Human caspases can be activated by
A) irreparable DNA damage or protein misfolding.
B) infrequency of cell division.
C) high concentrations of vitamin C.
D) a death-signaling ligand being removed from its receptor.
E) electron transport.

Back 51

A) irreparable DNA damage or protein misfolding.

Front 52

54) If an adult person has a faulty version of the human-analog to ced-4 of the nematode, which of the following
might more likely result?
A) neurodegeneration
B) activation of a developmental pathway found in the worm but not in humans
C) a form of cancer in which there is insufficient apoptosis
D) webbing of fingers or toes
E) excess skin exfoliation

Back 52

C) a form of cancer in which there is insufficient apoptosis