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

Question 1

From which molecule are steroids derived?

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

Answer 1

B

Question 2

What kinds of responses have NOT been observed when signals traveling down signaling pathways reach their target proteins?

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 2

C

Question 3

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 3

C

Question 4

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

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

Question 5

What is the largest protein superfamily encoded by animal genomes?

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

Question 6

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 7

The Gprotein-coupled receptor family of proteins often contain seven ____________________________ as a structural motif.

A)tyrosine-methionine dipeptides
B)transmembrane β-pleated sheets
C)transmembrane α-helices
D)methionine-tryptophan dipeptides
E)nucleotides attached

Question 8

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 9

What is the origin of virtually all of the signals that regulate cellular activities?

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

Question 10

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 11

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 12

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 13

Which of the following is NOT generally characteristic of 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

If a hormone receptor is degraded along with its ligand after internalization, what is the effect on the cell's ability to respond to the hormone?

A)The response is enhanced.
B)The cell has increased sensitivity to subsequent stimuli.
C)The cell has decreased sensitivity to subsequent stimuli.
D)The cell exhibits no change in responsiveness to subsequent stimuli.

Question 15

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)an activator
B)an effector
C)an affector
D)a refractor
E)a generator

Question 16

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 17

When a signal is initiated by the binding of an extracellular ligand, what is the immediate outcome of that signal?

A)A protein in the middle of an intracellular signaling pathway is activated.
B)A protein at the top of an intracellular signaling pathway is activated.
C)A protein at the top of an extracellular signaling pathway is activated.
D)A protein at the top of an intracellular signaling pathway is deactivated.
E)A protein at the bottom of an intracellular signaling pathway is activated.

Question 18

Which of the following processes is NOT reported to be regulated by eicosanoids?

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

Question 19

Which molecule below is NOT likely to act as either a neurotransmitter or hormone?

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

Question 20

What allows efficient recognition ofextracellular signaling molecules by receptros on the responding cell's surface?

A)low affinity binding with the signaling molecule
B)high affinity binding with the signaling molecule
C)denaturing of the signaling molecule
D)stabilization of the signaling molecule
E)infiltration of the signaling molecule

Question 21

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 22

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

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

Question 23

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 24

What happens to cells if 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 temporarily lose sensitivity for the ligand in question.
D)The cells remain sensitive to the ligand in question.
E)The cells expand.

Question 25

Which of the enzymes below does diacylglycerol (DAG)recruit and activate?

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

Question 26

Which heterotrimeric G proteins couple receptors to adenylyl cyclase via the activation of GTP-bound G_α subunits?

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

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

What role doescarbon number 1 of the inositol ring of phosphatidylinositol play?

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

Question 29

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 30

Which heterotrimeric G proteins are less well characterized than the other G protein families and are associated with excessive cell proliferation and malignant transformations when activated inappropriately?

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

Question 31

Which heterotrimeric G proteins function by inhibiting adenylyl cyclase?

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

Question 32

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 33

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

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 34

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 35

Which cells secrete epinephrine?

A)α-cells in the pancreas
B)β-cells in the pancreas
C)ɤ-cells in the pancreas
D)cortical cells in the adrenal gland
E)medullary cells in the adrenal gland

Question 36

In what form do animal cells store glucose?

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

Question 37

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

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

Question 38

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 39

________ are asmall 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 40

How is signaling by an activated G_α 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_α subunit releases GDP and binds GTP.

Question 41

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 42

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 43

Accessory proteins that bind to inactive monomeric G proteins and stimulate dissociation of the bound GDP are called:

A)GAPs
B)GEFs
C)GDIs
D)RASps
E)MAPs

Question 44

What kind of enzyme activity does the Ras protein display?

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

Question 45

The size of a biosensor can be:

A)at the molecular level, such as a protein-based GPCR receptor signal monitor
B)device-sized, like a blood glucose level detector
C)cell-based to detect human and plant pathogens
D)all choices are correct

Question 46

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 47

Where are the olfactory receptor cells located?

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

Question 48

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 49

Which of the following features is a requirement for 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 50

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 51

_________ 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 52

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

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

Question 53

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 H⁺ ion 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 54

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 proteins that usually dimerize.
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 55

Which of the following is NOT currently an application for biosensors?

A)monitoring of blood glucose levels
B)detection of pollutants in the environment
C)detection of contaminants in the foods we eat
D)indicator of food spoilage microbes in the air

Question 56

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 57

Which characteristic below is essential for a biosensor to function effectively?

A)ability to detect a wide range of similar chemicals as a single input
B)fluctuation of accuracy as environmental conditions vary
C)stability in the face of environmental factors such as temperature fluctuations
D)ability to detect chemicals only when they are present in large concentrations

Question 58

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 59

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 60

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 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

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 63

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 64

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 65

The auxin response factor (ARF)family members are believed to encode _______________.

A)G proteins
B)ubiquitins
C)transcription factors
D)gene repressors

Question 66

The enzyme 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 67

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

Question 68

Which of the following signaling methods is absent in plants but present in other eukaryotes?

A)MAP kinase pathway
B)Ca²⁺ signaling
C)phosphoinositide signaling
D)cyclic nucleotides
E)extracellular receptors

Question 69

Which was NOT an observation made in the initial experiments that revealed effects of auxin signaling?

A)grass seedlings exposed to overhead light bent towards the darkest region of their environment
B)grass seedlings whose blade tips were removed could not exhibit movement or bending
C)grass seedlings exposed to laterally-placed light bent towards the light source
D)grass seedlings tips and bases behaved differently in response to light stimulus

Question 70

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 71

Two αβ heterodimers of the insulin receptor are held together by ____ between the _______.

A)ionic bonds, α chains
B)ionic bonds, β chains
C)disulfide bonds, α chains
D)disulfide bonds, β chains
E)disulfide bonds, α chain of one heterodimer and the β chain of the other

Question 72

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 73

What is responsible for deactivating glycogen synthase kinase-3?

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

Question 74

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 75

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 76

What can cause the stockpiles of intracellular calcium ions to be depleted?

A)periods of repeated cellular responses
B)a paucity of cellular responses
C)crystallization of calcium ions with chlorine ions
D)crystallization of calcium with phosphate ions

Question 77

Who was one of the first scientists to observe the effects of the plant hormone auxin?

A)Gregor Mendel
B)Charles Darwin
C)Louis Pasteur
D)Barbara McClintock

Question 78

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 79

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 phosphotyrosine binding domain
C)a long tail containing tyrosine phosphorylation sites
D)a C-terminal PH domain
E)a PKB domain

Question 80

Accessory proteins that maintain monomeric G proteins in an inactive state by inhibiting GDP-GTP exchange are called:

A)GAPs
B)GEFs
C)GDIs
D)RASps
E)MAPs