Deck 15: Cell Signaling and Signal Transduction: Communication Between Cells

Question 1

How do cells in the body of a multicellular organism usually communicate with each other?

A)intracellular messenger molecules
B)direct connection by cells through long projections
C)extracellular messenger molecules
D)electrical signals between cells
E)ion transport between cells

Answer 1

C

Question 2

What allows receptors for extracellular signaling molecules present on the responding cell's surface to recognize such molecules so readily?

A)They bind the signaling molecules with low affinity.
B)They bind the signaling molecules with high affinity.
C)They denature the signaling molecules.
D)They stabilize the signaling molecules.
E)They infiltrate the signaling molecules.

Answer 2

B

Question 3

What kinds of responses are not initiated when signals traveling down signaling pathways reach their target proteins,which are usually involved in basic cellular processes?

A)a change in gene expression
B)a change in ion permeability
C)cessation of DNA synthesis and degradation of DNA
D)the death of the cell
E)an alteration of the activity of metabolic enzymes

Answer 3

C

Question 4

Sometimes an enzyme is activated by a receptor and brings about the cellular response by generating a second messenger.Such an enzyme is called a(n)__________.

A)activator
B)effector
C)affector
D)refractor
E)generator

Question 5

Which molecule below is unlikely to act as either a neurotransmitter or hormone?

A)glucose
B)glycine
C)dopamine
D)eicosanoids
E)thyroid hormone

Question 6

Which of the following processes is not regulated by eicosanoids?

A)pain
B)inflammation
C)blood pressure
D)blood clotting
E)neurotransmission

Question 7

Which amino acids are known to be phosphorylated by protein kinases?

A)tyrosine,threonine,glycine
B)threonine,serine,tryptophan
C)serine,threonine,tyrosine
D)phenylalanine,serine,tyrosine
E)serine,leucine,tyrosine

Question 8

The overall process in which information carried by extracellular messenger molecules is translated into changes that occur inside the cell is called ___________.

A)signal digestion
B)signal destruction
C)signal interaction
D)signal transduction
E)signal induction

Question 9

Why are G-protein coupled receptors often known as 7TM receptors?

A)They have 7 tyrosine-methionine dipeptides in their structure.
B)They have 7 transmembrane $\beta$ -pleated sheets.
C)They have 7 transmembrane $\alpha$ --helices.
D)They have 7 methionine-tryptophan dipeptides in their structure.
E)They have 7 nucleotides attached to their structure.

Question 10

Which signaling molecules are nonpolar molecules containing 20 carbons that are derived from a fatty acid named arachidonic acid?

A)eicosanoids
B)steroids
C)acetylcholine
D)acetylsalicylic acid
E)epinephrine

Question 11

Which molecule below does not act as a neurotransmitter and a hormone?

A)glutamate
B)glycine
C)dopamine
D)eicosanoids
E)thyroid hormone

Question 12

What is the largest protein superfamily encoded by animal genomes?

A)G-protein coupled receptors
B)RTKs
C)steroid receptors
D)tubulin superfamily
E)ligand-gated channels

Question 13

Which of the following is (are)not characteristics of the pathways activated by second messengers?

A)Each signaling pathway consists of a series of distinct proteins that operate in sequence.
B)Each protein in the pathway typically acts by altering the conformation of the previous (upstream)protein in the series,an event that activates or inhibits the protein.
C)Alterations in the conformations of signaling proteins are often accomplished by protein kinases and protein phosphatases that,respectively,add or remove phosphate groups from other proteins.
D)Some phosphatases and protein kinases in the pathway have numerous proteins as their substrates;others act on only a single protein substrate or a single amino acid of a protein substrate.
E)Many of the protein substrates of the pathway enzymes are enzymes themselves,like other kinases and phosphatases,but they include ion channels,transcription factors and various regulatory molecules.

Question 14

At which site do virtually all of the signals that regulate the activities in which a cell is engaged originate?

A)at the cell surface
B)in the nucleus
C)in the nucleolus
D)in the endoplasmic reticulum
E)in the cell wall

Question 15

Which of the following are not natural ligands that bind to G-protein coupled receptors?

A)hormones
B)neurotransmitters
C)chemoattractants
D)opium derivatives
E)steroid hormones

Question 16

From what molecule are the steroids derived?

A)CO₂
B)cholesterol
C)glucose
D)phospholipids
E)glucagons

Question 17

Where are steroid receptors generally located and where do they bind the steroid hormone once it enters the cell?

A)They are located and bind the steroids in the cytoplasm.
B)They are located and bind the steroids in the middle of the cell membrane.
C)They are located and bind the steroids on the extracellular membrane surface.
D)They are located and bind the steroids on the intracellular membrane surface.
E)The receptors are located in the cytoplasm but they bind their ligands in the lysosomes.

Question 18

What role do activated steroid receptors play in the cell?

A)activation of inactive enzymes
B)inactivation of active enzymes
C)ligand-regulated transcription factors
D)opening of specific ion channels
E)activation of cytoplasmic proteins

Question 19

For many years,_______ was the only member of the GPCR superfamily to have its X-ray crystal structure determined.

A)rhodopsin
B)the steroid receptor
C)the insulin receptor
D)the glucagon receptor
E)the endocrine receptor

Question 20

Why does rhodopsin have an unusually stable structure for a GPCR?

A)Its ligand is permanently bound to the protein.
B)A retinal group is permanently bound to the protein.
C)The protein molecule can only exist in a single conformation in the absence of a stimulus.
D)The protein molecule can only exist in a single conformation in the dark.
E)All of these are correct.

Question 21

In order to begin desensitization,the ________ domain of the activated G protein-coupled receptor is phosphorylated by a specific enzyme called a(n)________.

A)extracellular,G protein-coupled receptor kinase
B)extracellular,G protein-coupled receptor phosphatase
C)cytoplasmic,G protein-coupled receptor kinase
D)cytoplasmic,G protein-coupled receptor phosphatase
E)extracellular,GRK

Question 22

What enzyme below does diacylglycerol (DAG)recruit and activate?

A)phosphatidylinositol (PI)-specific phospholipase C- $\beta$
B)protein kinase A
C)protein kinase C
D)glycogen phosphorylase
E)phosphorylase kinase

Question 23

Conformational shift in the  subunit of the G protein

A)6 - 3 - 5 - 1 - 2 - 4 - 7
B)3 - 6 - 5 - 1 - 7 - 2 - 4
C)6 - 3 - 5 - 1 - 7 - 2 - 4
D)6 - 7 - 3 - 5 - 1 - 2 - 4
E)6 - 3 - 5 - 1 - 7 - 4 - 2

Question 24

The subunits of the heterotrimeric G protein are called ___________ subunits.

A) $\alpha$ , $\beta$ and $\chi$
B) $\alpha$ , $\beta$ and $\delta$
C) $\alpha$ , $\beta$ and $\gamma$
D) $\alpha$ , $\gamma$ and $\delta$
E) $\gamma$ , $\delta$ and $\eta$

Question 25

Where is the guanine nucleotide-binding site of the G protein located?

A)on the G _$\alpha$ subunit
B)on the G _$\beta$ subunit
C)on the G _$\gamma$ subunit
D)on the G _{$\beta$$\gamma$} subunit
E)on all three subunits

Question 26

While bound to phosphorylated GPCRs,to what else can arrestins bind?

A)G proteins
B)clathrin molecules in clathrin-coated pits
C)other arrestins
D)hormones
E)GRKs

Question 27

What does the interaction between arrestin and clathrin promote?

A)the uptake of free hormone
B)the uptake of phosphorylated GPCRs into the cell by exocytosis
C)the uptake of phosphorylated GPCRs into the cell by endocytosis
D)the expulsion of phosphorylated GPCRs from the cell by exocytosis
E)the secretion of GPCRs

Question 28

The process that blocks active receptors from turning on additional G proteins is called ________.

A)hypersensitization
B)desensitization
C)hyposensitization
D)deactivation
E)sensitivitization

Question 29

How is signaling by an activated G _$\alpha$ subunit terminated?

A)The bound GTP is hydrolyzed to GMP.
B)The bound GDP is hydrolyzed to GTP.
C)The bound GTP is hydrolyzed to GDP.
D)The bound GDP is phosphorylated to GTP.
E)The G _$\alpha$ subunit releases GDP and binds GTP.

Question 30

What group of enzymes phosphorylates most of the carbons on inositol?

A)phospholipases
B)phosphoinositide kinases
C)phosphorylases
D)phosphodiesterases
E)phosphatases

Question 31

________ form a small group of proteins that bind to GPCRs and compete for binding to those GPCRs with heterotrimeric G proteins.

A)Stablins
B)Arrestins
C)Monomeric G proteins
D)G protein-coupled receptor kinases
E)Desensitizers

Question 32

GRKs are a small family of ________ protein kinases,most of which are localized to the _______ surface of the plasma membrane.

A)serine-threonine,cytoplasmic
B)serine-threonine,extracellular
C)tyrosine,cytoplasmic
D)tyrosine,extracellular
E)serine-tyrosine,cytoplasmic

Question 33

G _$\alpha$ -subunit with its attached GTP activates an effector like adenylyl cyclase.

A)4 - 5 - 2 - 6 - 3 - 1
B)5 - 4 - 2 - 6 - 3 - 1
C)4 - 6 - 2 - 5 - 3 - 1
D)4 - 5 - 2 - 3 - 1 - 6
E)1 - 5 - 2 - 4 - 3 - 6

Question 34

Which heterotrimeric G proteins are less well characterized than the other G protein families and have had their inappropriate activation associated with excessive cell proliferation and malignant transformations?

A)G_s family
B)G_q family
C)G_i family
D)G_12/13 family
E)G_r family

Question 35

What happens to cells if the receptors are degraded once they are internalized?

A)The cells are able to make a magnified response to the same stimulus from the ligand in question.
B)The cells permanently lose sensitivity for the ligand in question.
C)The cells lose,at least temporarily,sensitivity for the ligand in question.
D)The cells remain sensitive to the ligand in question.
E)The cells expand.

Question 36

What recruits cytoplasmic GRKs (G protein-coupled receptor kinases)to the plasma membrane?

A)inhibition of certain G proteins
B)destruction of the GPCRs
C)activation of GPCRs
D)inhibition of the GPCRs
E)destruction of the hormone

Question 37

Arrestin binding to GPCRs __________.

A)causes the binding of additional G proteins
B)prevents further activation of additional G proteins
C)causes denaturation of G proteins
D)stabilizes G proteins
E)stabilizes GPCRs

Question 38

Which heterotrimeric G proteins couple receptors to adenylyl cyclase via the activation of GTP-bound G _$\alpha$ subunits?

A)G_s family
B)G_q family
C)G_i family
D)G_12/13 family
E)G_r family

Question 39

What is the function of carbon number 1 on the inositol ring of phosphatidylinositol?

A)It binds to steroid receptors.
B)It joins inositol to diacylglycerol.
C)It joins a phosphate group to diacyglycerol.
D)It joins glucose to diacylglycerol.
E)It joins two diacyglycerol molecules together.

Question 40

Which heterotrimeric G proteins function by inhibiting adenylyl cyclase?

A)G_s family
B)G_q family
C)G_i family
D)G_12/13 family
E)G_r family

Question 41

The effect of inositol triphosphate is usually transient because __________.

A)it is so stable
B)it is rapidly inactivated enzymatically
C)it is slowly activated enzymatically
D)it is so big
E)it is so small

Question 42

Which of the following features would be a requirement for a receptor that exhibits ligand-mediated dimerization?

A)The ligand has only one binding site for receptors.
B)The ligand has two binding sites for receptors.
C)The receptor must have a phenylalanine residue in a specific location.
D)The receptor must have a molecular weight of 50,000 daltons.
E)Ligand binding causes a conformational shift that reveals a binding site for another receptor.

Question 43

Genes that enable viruses to transform normal cells into tumor cells are called _________.

A)oncogenes
B)cancogenes
C)haplogenes
D)tumor enhancer genes
E)transformer genes

Question 44

________ is a small protein that is linked covalently to other proteins,thereby marking those proteins for internalization or degradation.

A)Chaperonin
B)Ubiquitin
C)Proinsulin
D)Transcriptin
E)Tubulin

Question 45

Which cells secrete epinephrine?

A) $\alpha$ -cells in the pancreas
B) $\beta$ -cells in the pancreas
C) $\Delta$ -cells in the pancreas
D)cortical cells in the adrenal gland
E)medulla cells in the adrenal gland

Question 46

Why do colds cause us to lose some of our appreciation for the taste of food?

A)The symptoms of colds interfere with the stimuli reaching the taste bud receptors,thus dulling the perception of taste.
B)The symptoms of colds prevent stimuli from reaching olfactory neurons efficiently,thus dulling the perception of taste.
C)Cold viruses raise the firing threshold of olfactory neurons,thus dulling the perception of taste.
D)Cold viruses lower the firing threshold of olfactory neurons,thus dulling the perception of taste.
E)Cold viruses denature olfactory neurons,thus dulling the perception of taste.

Question 47

In what form do animal cells store glucose?

A)glucogen
B)glycogen
C)agarose
D)amylose
E)amylopectin

Question 48

What event is usually responsible for terminating signal transduction by RTKs?

A)dephosphorylation of the receptor
B)degradation of the ligand
C)receptor internalization
D)phosphorylation of the receptor
E)acetylation of the receptor

Question 49

What might cause a person to have an inability to detect a particular chemical in the environment that most other members of the population can perceive?

A)mutations is a specific gene encoding the odorant receptor for that particular chemical
B)mutations in the genes for all odorant molecules
C)mutations in the genes for G proteins
D)mutations in the genes for neurotransmitters
E)mutations in the gene for one neurotransmitter

Question 50

Where are the olfactory receptor cells located?

A)the brain
B)the nasal septum
C)the nasal mucosa
D)the surface of the tongue
E)the nasal serosa

Question 51

Viruses that carry their genetic information in the form of RNA are called ________.

A)viria
B)retroviruses
C)reverse transcriptases
D)retrons
E)provirions

Question 52

Perception of sour tastes depends upon _________.

A)a compound interacting with a G protein coupled receptor on the receptor cell surface
B)sodium ions in the food that enter cation channels in the taste receptor plasma membrane,leading to a membrane depolarization
C)protons in the food that enter cation channels in the taste receptor plasma membrane,leading to a membrane depolarization
D)potassium ions in the food that enter cation channels in the taste receptor plasma membrane,leading to a membrane depolarization
E)protons in the food that enter cation channels in the taste receptor plasma membrane,leading to a membrane hyperpolarization

Question 53

Which hormone is secreted by $\alpha$ -cells in the pancreas in response to low blood glucose levels?

A)insulin
B)glycogen
C)glucagon
D)epinephrine
E)somatostatin

Question 54

How many high-affinity sweet-taste receptors have been identified?

A)none
B)30
C)1
D)10
E)3

Question 55

What phosphorylates the tyrosine residues found on docking proteins?

A)a G protein coupled receptor
B)a receptor protein-tyrosine kinase
C)a cytoplasmic protein-tyrosine kinase
D)adaptor proteins
E)receptor protein phosphatases

Question 56

Which statement below is an accurate description of receptor-mediated dimerization?

A)Ligands act as allosteric regulators that turn on the ability of their receptors to form dimers.
B)Ligands act as allosteric inhibitors that turn on the ability of their receptors to form dimers.
C)Ligands act as allosteric inhibitors that turn off the ability of their receptors to form dimers.
D)Ligands act as allosteric regulators that turn off the ability of their receptors to form dimers.
E)Ligands act as bridging factors that allow the receptors to dimerize.

Question 57

_________ are enzymes that phosphorylate specific tyrosine residues on protein substrates.

A)Protein tyrosinases
B)Protein-tyrosine kinases
C)Tyrosine pronases
D)Proteokinases
E)Tyrokinases

Question 58

Once the kinase domain of receptor protein-tyrosine kinase has been activated,what does the activated receptor protein-tyrosine kinase do?

A)The receptor subunits denature.
B)Each receptor subunit phosphorylates its partner on tyrosine residues found in regions adjacent to the kinase domain.
C)Each receptor subunit phosphorylates itself on tyrosine residues found in regions adjacent to the kinase domain.
D)The receptor subunits dephosphorylate each other.
E)The receptor subunits refold into a more effective conformation.

Question 59

Which of the following contains an SH2 domain together with a tyrosine phosphorylation site that can act as a binding site for the SH2 domain of an identical molecule leading to dimerization?

A)adaptor proteins
B)docking proteins
C)transcription factors
D)enzymes
E)All of these are correct.

Question 60

Which of the following supports the ligand-mediated model of receptor dimerization?

A)Some growth and differentiation factors like PDGF or CSF-1 are composed of two similar or identical disulfide-linked subunits,each of which has a binding site for a receptor.
B)Ligands have been found to be small proteins.
C)Ligands have been found to be steroid hormones.
D)Ligands were found to bind to each other
E)Receptors have been shown to have multiple binding sites for ligands.

Question 61

Type I diabetes is caused by ________.

A)degradation of insulin in the bloodstream
B)an inability to produce insulin
C)a decrease in the ability of target cells for insulin to respond to the presence of the hormone
D)insulin resistance
E)an overproduction of insulin

Question 62

How is Ras activity turned off?

A)It is turned off by phosphorylation.
B)It is turned off by hydrolysis of its bound GTP to GDP.
C)It is turned off by hydrolysis of its bound GDP to GTP.
D)It is turned off by an allosteric inhibitor.
E)It is turned off by hydrolysis of its bound GTP to GMP.

Question 63

The enzyme below that has been identified as a negative regulator of glycogen synthase is ______.

A)glycogen phosphorylase
B)glycogen phosphorylase kinase
C)glycogen synthase kinase-3
D)insulin synthase kinase
E)protein kinase A

Question 64

In cells exposed to stressful stimuli,like X-rays or damaging chemicals,what response does the MAP kinase cascade coordinate?

A)cell proliferation
B)withdrawal from the cell cycle
C)rapid differentiation
D)slowing of the Krebs cycle
E)a loss of sensory ability

Question 65

Ora1 is a tetrameric _______ that has been identified as being involved in a particular type of inherited human immune deficiency that results from a lack of Ca2+ stores in ________.

A)Ca^2+--ion channel,B lymphocytes
B)Ca^2+--ion pump,B lymphocytes
C)Ca^2+-ion channel,T lymphocytes
D)Ca^2+--ion pump,T lymphocytes
E)Ca^2+--ion channel,macrophages

Question 66

What holds Ras at the inner surface of the plasma membrane?

A)weak interactions with the phospholipid head groups
B)weak interactions with integral membrane proteins
C)hydrophilic interactions of the Ras protein with the interior of the phospholipid bilayer
D)attachment to a lipid group that is embedded in the inner leaflet of the bilayer
E)attachment to a carbohydrate group that is embedded in the inner leaflet of the bilayer

Question 67

Specificity in MAP kinase pathways is sometimes achieved by spatial localization of the pathway's component proteins.Spatial localization of these components is done by structural (i.e. ,nonenzymatic)proteins called _____________.

A)sequestration proteins
B)partitioning proteins
C)scaffolding proteins
D)framework proteins
E)spatial organization proteins

Question 68

What part of an insulin-receptor substrate binds to tyrosine phosphorylation sites on the activated insulin receptor?

A)an N-terminal PH domain
B)a PTB domain
C)a long tail containing tyrosine phosphorylation sites
D)a C-terminal PH domain
E)a PKB domain

Question 69

Two $\alpha$$\beta$ heterodimers of the insulin receptor are held together by ____ between the _______.

A)ionic bonds, $\alpha$ chains
B)ionic bonds, $\beta$ chains
C)disulfide bonds, $\alpha$ chains
D)disulfide bonds, $\beta$ chains
E)disulfide bonds, $\alpha$ chain of one heterodimer and the  chain of the other

Question 70

What kind of enzyme is the RAS gene product,the Ras protein?

A)an ATPase
B)a kinase
C)a phosphodiesterase
D)a GTPase
E)a phosphatase

Question 71

Following a nerve impulse,what triggers the opening of plasma membrane voltage-gated Ca2+ channels?

A)membrane hyperpolarization
B)binding of an appropriate ligand
C)membrane depolarization
D)membrane hypopolarization
E)binding of K⁺ ions

Question 72

What is activated by calcium ions entering an egg cell just after fertilization?

A)protein kinase A
B)insulin
C)cyclin-dependent kinases that drive the zygote toward its first mitotic division
D)cyclin-dependent kinases that drive the zygote toward its first meiotic division
E)glucagon-dependent kinases that drive the zygote toward its first mitotic division

Question 73

Among the agents that can cause ryanodine receptors to open are _______ ions,in a phenomenon called _______.

A)calcium,calcium-integrated calcium release
B)calcium,calcium-induced calcium release
C)potassium,potassium-induced calcium release
D)chlorine,chlorine-induced calcium release
E)copper,copper-induced calcium release

Question 74

In which organism below has calmodulin not been found?

A)plants
B)animals
C)bacteria
D)yeasts
E)humans

Question 75

The concentration of calcium ions in the ER lumen,the plant cell vacuole and the extracellular space are on average more than _______ times higher than in the cytosol.

A)10
B)100
C)1,000
D)10.000
E)1,000,000

Question 76

What is responsible for deactivating glycogen synthase kinase-3?

A)its phosphorylation by PKB
B)its dephosphorylation by protein phosphatase 1
C)its dephosphorylation by PKB
D)its phosphorylation by protein phosphatase 1
E)its degradation by PKB

Question 77

What is the name of a calcium-binding protein that acts in conjunction with calcium to bring about the responses associated with cytoplasmic rises in calcium ion concentration?

A)calpectin
B)calmodulin
C)calcariain
D)callistin
E)modulocalcin

Question 78

What generally triggers the release of calcium ions by ryanodine receptors?

A)potassium efflux
B)sodium influx
C)an action potential
D)IP₃ release
E)IP₃ uptake

Question 79

What is the reason for the withdrawal of cells from the cell cycle after exposure to stressful stimuli,like X-rays and damaging chemicals?

A)It gives the cell time to repair damage resulting from such adverse conditions.
B)It allows the cell to initiate programmed cell death.
C)It allows cells to initiate sodium transport.
D)It allows the cell to secrete defensive chemicals.
E)It gives the cell time to switch its developmental pathways.

Question 80

How is the distribution of free calcium ions in the living cell detected?

A)fluorescent probes that emit light in the presence of calcium ions
B)antibodies bound to ferritin
C)an electron microscope
D)autoradiography and the distribution of radioisotope
E)NMR imaging