Deck 23: Signal Transduction Mechanisms: Iimessengers and Receptors

Question 1

Previous experiments have not conclusively demonstrated XFF is the alien epinephrine,so you decide to investigate other XFF properties using radioactive XFF.Which of the following XFF behaviors confirm that XFF is similar to estrogen?

A)XFF binds only to the cell surface.
B)XFF diffuses into the cell cytoplasm.
C)XFF is internalized by receptor-mediated endocytosis.
D)Ryanodine blocks the interaction of XFF with cells.
E)Opioids block the interaction of XFF with cells.

Answer 1

B

Question 2

Each of the following activates a receptor tyrosine kinase except

A)EGF.
B)PDGF.
C)TGFβ
D)FGF.
E)Insulin.

Answer 2

C

Question 3

The interleukin-2 (IL-2)growth factor interacts with receptors on

A)embryonic cells.
B)cytotoxic T lymphocytes.
C)mesenchymal cells.
D)smooth muscle cells.
E)epithelial cells.

Answer 3

B

Question 4

Reception of a signal released by the same cell is which of the following types of signaling?

A)paracrine
B)endocrine
C)autocrine
D)juxtacrine
E)exocrine

Question 5

Each of the following ligands binds to an intracellular receptor except

A)cortisol.
B)retinoic acid.
C)thyroid hormone.
D)epinephrine.
E)estrogen.

Question 6

You add a large amount of XFF to cultured alien liver cells.Which of the following would confirm that XFF is the alien equivalent of human epinephrine?

A)increased cell division
B)decreased cell division
C)glycogen breakdown
D)increased glucose uptake
E)insensitivity to insulin

Question 7

Each of the following is correct about cholera and its effect on G-protein-adenylyl cyclase activity except

A)Vibrio cholera bacteria colonize the gut.
B)Cholera toxin is secreted by Vibrio cholera bacteria.
C)Intestinal cells infected with cholera toxin import abnormally high levels of salts and fluids into the bloodstream.
D)Cholera toxin alters G_sα so that it no longer hydrolyzes GTP.
E)Intestinal cells infected with cholera toxin maintain abnormally high cAMP levels.

Question 8

Each of the following is a G-protein coupled receptor (GPCR)or type of GPCR except

A)steroid hormone receptors.
B)opioid receptors.
C)thyroid-stimulating hormone receptors.
D)olfactory receptors.
E)β-adrenergic receptors.

Question 9

Which of the following would be correctly described as a juxtacrine signaling?

A)a signal that requires physical contact between cell
B)a signal that acts on the cell that produces it
C)a signal that diffuses over long distances from the producing cell
D)a signal that diffuses over short distances from the producing cell
E)a hormonal signal

Question 10

To test whether the XFF signal system is similar to that of epinephrine,you microinject a nonhydrolyzable analogue of GTP into an XFF-responsive cell.If the XFF mechanism is similar to that of epinephrine,you would expect the cellular response to be

A)blocked completely.
B)prolonged.
C)delayed.
D)50 percent of normal.
E)It is not possible to predict without knowing how many receptors are present on the cell.

Question 11

Which of the following is a lipophilic primary message that crosses the plasma membrane and interacts with a cytosolic receptor?

A)estrogen
B)EGF
C)pertussis toxin
D)TGFβ
E)PDGF

Question 12

Desensitization of a cell to a ligand may involve each of the following except

A)destruction of the ligand.
B)decrease in receptor ability to activate intracellular signaling pathway.
C)receptor destruction.
D)receptor endocytosis.
E)decrease in receptor affinity for the ligand.

Question 13

Compounds that inhibit receptors by preventing the natural messenger from binding are known as

A)agonists.
B)arrestins.
C)sildenafils.
D)syndecans.
E)antagonists.

Question 14

The concentration of the primary messenger (ligand)in the bloodstream changes from <10⁻⁹ M when the signal is not being secreted to 10⁻⁷ M when it is being secreted.Which of the following K_ds for binding that ligand would be optimal for a receptor involved in a responsive signaling system?

A)10⁻¹⁰
B)10⁻⁹
C)10⁻⁸
D)10⁻⁷
E)10⁻⁶

Question 15

In a hormone-stimulated signaling system,the concentration of hormone exposed to the receptor is

A)always equal to the receptor K_d for binding the hormone.
B)never equal to the receptor K_d for binding the hormone.
C)below the receptor K_d for binding the hormone before stimulation of hormone secretion.
D)above the receptor K_d for binding the hormone before stimulation of hormone secretion.
E)always constant.

Question 16

Each of the following is a step in the epinephrine-cAMP pathway in which the signal is amplified except

A)receptor activation of G-protein.
B)G-protein activation of adenylyl cyclase.
C)adenylyl cyclase production of cAMP.
D)protein kinase A phosphorylation of target proteins.

Question 17

Inhibitors of which of the following would interfere with nitric oxide stimulation of cardiac artery dilation through relaxation of smooth muscle cells?

A)protein kinase G.
B)nitric oxide synthase
C)guanylyl cyclase
D)calmodulin
E)Inhibitors of all of the above would interfere with nitric oxide stimulation.

Question 18

Each of the following is an intracellular messenger except

A)calcium ions.
B)IP3.
C)DAG.
D)cAMP.
E)PDGF.

Question 19

Which of the following would best be used to demonstrate XFF is most like EGF?

A)exposure of cells to radioactive XFF
B)receptor binding assays
C)microinjection into cells of nonhydrolyzable GTP analogues
D)exposure of cells to ryanodine
E)exposure of cells to tyrosine kinase inhibitors

Question 20

You are seeking a new anti-inflammatory drug to inhibit local responses to stress and injury.Which of the following activities would you look for in a potential anti-inflammatory agent?

A)stimulates release of prostaglandins
B)blocks adenylate cyclase activity
C)blocks an enzyme associated with arachidonic acid production
D)stimulates the activation of platelets
E)increases estrogen secretion

Question 21

Each of the following is a characteristic of calmodulin except

A)It binds two calcium ions at each end of the protein.
B)When activated by calcium ion binding,it wraps around proteins that have calmodulin binding sites.
C)It can activate specific kinases and phosphatases.
D)It has a very high affinity for calcium ions,and binds calcium ions irreversibly.
E)All are characteristics of calmodulin.

Question 22

You recently identified a molecule that you believe is a primary messenger for a signal transduction mechanism.All you know about this ligand is that it is hydrophilic.Where would you expect to find initial interaction of the molecule with its receptor?

A)on the outer surface of the plasma membrane
B)within the cytoplasm of the cell
C)within the nucleus of the cell
D)on the cytoplasmic side of the plasma membrane
E)in endosome vesicles

Question 23

cAMP affects cell activities by interacting directly with

A)adenylyl cyclase.
B)protein kinase A regulatory subunits.
C)protein kinase A catalytic subunits.
D)cAMP phosphodiesterase.
E)calmodulin.

Question 24

Kinases and phosphatases are essential in the cell because they directly

A)turn proteins "on and off" through changes in phosphorylation status.
B)bind hydrophobic hormones in the cytoplasm.
C)bind and release calcium ions.
D)destroy IP₃,turning off that signaling pathway.
E)activate and repress genes.

Question 25

Which of the following is a synthetic protein produced from engineered DNA that is used to determine whether cytosolic calcium fluxes are associated with signal transduction in a particular cell type?

A)sildenafil
B)ionomycin
C)A23187
D)fura-2
E)a cameleons

Question 26

The low level of cytosolic calcium ions in unactivated cells is established by which of the following?

A)calmodulin
B)calcium ATPases
C)kinases
D)phosphatases
E)phospholipase C

Question 27

Each of the following is a plant hormone except

A)brassinosteroids
B)abscisic acid.
C)ethylene.
D)All the above are plant hormones.
E)None of the above are plant hormones.

Question 28

cAMP activates

A)protein kinase A.
B)protein kinase B.
C)protein kinase C.
D)protein kinase G.
E)MAPK.

Question 29

Each of the following is a second messenger except

A)cyclic adenosine monophosphate.
B)inositol trisphosphate.
C)diacylglycerol.
D)epinephrine.
E)calcium ions.

Question 30

Which of the following is the correct order of steps in the EGF-cAMP signaling pathway?

A)ligand binding-G-protein activation- adenylyl cyclase activation-cAMP production-protein kinase A activation
B)ligand binding-protein kinase A activation-G-protein activation-adenylyl cyclase activation-cAMP production
C)G-protein activation-ligand binding-adenylyl cyclase activation-cAMP production-protein kinase A activation.
D)ligand binding-G-protein activation-adenylyl cyclase activation-cAMP production-protein kinase A activation
E)ligand binding-adenylyl cyclase activation-G-protein activation-cAMP production-protein kinase A activation

Question 31

Dilation of blood vessels is regulated by the second messenger

A)cAMP.
B)Ca²⁺.
C)IP₃.
D)CO₂.
E)NO.

Question 32

You are investigating a cell activity that you suspect is activated by a rise in intracellular calcium ions.Which of the following agents could you use to cause an increase in intracellular calcium in the cells you are studying?

A)cameleon
B)A23187
C)phorbol ester
D)sildenafil
E)NO

Question 33

Kinase enzymes

A)add phosphate groups.
B)always inhibit target molecule activity.
C)bind tightly by wrapping around a target molecule to regulate its activity.
D)remove phosphate groups.
E)metabolize glucose.

Question 34

Protein kinase C (PKC)activity is involved in each of the following except

A)ion channel regulation.
B)cytoskeleton changes.
C)increase in cellular pH.
D)secretion of proteins and other substances.
E)PKC is involved in all of the above.

Question 35

Each of the following hormones is an amino acid derivative except

A)histamine.
B)norepinephrine.
C)prostaglandins.
D)epinephrine.
E)thyroxine.

Question 36

Each of the following is a correct cell-specific response of Epinephrine-cAMP signaling except

A)liver cell glycogen breakdown to glucose.
B)stronger heart muscle contraction.
C)stronger smooth muscle contraction.
D)inhibition of platelet activation during blood clotting.
E)increase in intestinal epithelial cell fluid secretion.

Question 37

Each of the following is true about Ras except

A)Ras is monomeric.
B)Ras activity is inhibited by GTPase activating proteins (GAPs).
C)Ras binds steroid hormones.
D)Ras is activated by Sos,a guanine nucleotide exchange factor.
E)Ras activates a cascade of phosphorylation events within the cell.

Question 38

IP₃ receptors are associated with

A)plasma membranes.
B)Golgi apparatus membranes.
C)mitochondrial membranes.
D)ER membranes.
E)endosome membranes.

Question 39

Which of the following would you expect to happen if you added EGF to a cell extract from which only the plasma membrane fraction has been removed?

A)cAMP will be produced.
B)G_sα will be activated.
C)Adenylyl cyclase will be activated.
D)Calcium ions will be released.
E)None of the above will happen.

Question 40

Phosphatase enzymes

A)add phosphate groups.
B)always inhibit target molecule activity.
C)bind tightly by wrapping around a target molecule to regulate its activity.
D)remove phosphate groups.
E)metabolize glucose.

Question 41

The α-subunit of a heterotrimeric G-protein is active when bound to ________.

Question 42

Which of the following proteins exerts direct control over the glycogen synthesis and breakdown pathways when epinephrine stimulates glycogen conversion to glucose in liver cells?

A)glycogen phosphorylase
B)phosphorylase kinase
C)protein kinase A
D)cAMP phosphodiesterase
E)glycogen synthase

Question 43

________ are genetically engineered proteins that respond directly to cytosolic calcium fluxes by changing their fluorescence intensity.

Question 44

________ nucleotides are common second messengers in animal cells.

Question 45

PTEN is a phosphatase that removes a phosphate group from ________,thereby preventing its activation of Akt kinase.

Question 46

What compounds or probes could you use to investigate (a)G-protein-mediated signal transduction,(b)nitric oxide signal transduction,and (c)calcium ion-dependent fluxes and effects.

Question 47

________ produces the second messengers IP₃ and diacylglycerol (DAG).

Question 48

________ is the messenger that regulates blood pressure by causing arterial smooth muscle relaxation.

Question 49

In heterotrimeric G-proteins,the ________ subunit stimulates adenylyl kinase.

Question 50

The coordinated response of cells to an array of different signals from the environment is known as ________.

Question 51

A mutation in RTK receptor that allows the receptor to bind the ligand and pair with a wild-type receptor but blocks signal transduction is classified as a ________ mutation,whereas a mutation that activates RTK pairing signal transduction even in the absence of ligand is classified as a ________ mutation.

Question 52

Following fertilization of animal eggs,________ are the second messengers that trigger egg activation.

Question 53

Cells can regulate precisely where signaling occurs within the cell (e.g.,in the yeast mating pathway)by association of the signal pathway proteins with a ________.

Question 54

In smooth muscle cells,acetylcholine stimulates activation of the enzyme ________,which cleaves ________ to form the second messengers ________ and ________.

Question 55

Types of regulators of G-protein signaling (RGS)proteins known as ________ accelerate termination of signaling by stimulating a G-protein to ________ GTP.

Question 56

Each of the following is a characteristic of hormones except

A)synthesis by endocrine tissue cells.
B)secretion directly into the bloodstream.
C)having a hormone-specific lifespan in the blood ranging from seconds to hours.
D)interacting with specific receptors on cells in target tissues throughout the body.
E)All are characteristics of endocrine hormones.

Question 57

Insulin-stimulated increase in glucose uptake and storage in cells is promoted by activation of each of the following except

A)Ras.
B)PI 3-kinase.
C)PTEN.
D)Akt kinase.
E)Glut4.

Question 58

EGF (epidermal growth factor)activates cell division by binding to ________.

Question 59

G_sα nucleotide exchange is stimulated by a ________,whereas Ras nucleotide exchange is stimulated by ________.

Question 60

G_sα activates ________.

Question 61

A strain of Drosophila known as dunce produces one-half the amount of cAMP phosphodiesterase found in wild-type flies,which causes a learning defect.Another strain of Drosophila known as rutabaga produces a defective adenylyl cyclase protein (one of the AC types expressed in most cells)and also causes a learning defect.A dunce-rutabaga double mutant fly has relatively normal learning.Explain these curious observations.

Question 62

Compare and contrast receptor tyrosine kinase (RTK)signaling pathways such as the EGF-Ras-MAPK pathway with serine/threonine kinase (S/TK)signaling pathways such as the TGF? pathway with respect to (a)receptors,(b)phosphorylation targets,(c)signal transduction from the plasma membrane through the cytoplasm to the nucleus,and (d)effects on gene regulation.

Question 63

Compare and contrast GPCR and RTK receptors with respect to (a)structure-especially the transmembrane region,(b)activation mechanism,(c)initial signal transduction across the membrane.

Question 64

Initial attempts to culture cells demonstrated that blood serum but not blood plasma provided factors that increased the viability and proliferation of the cultured cells.Explain.

Question 65

Theophylline,a methylxanthine like caffeine,is used to treat asthma.Explain the mechanism by which a methylxanthine can alleviate asthma symptoms resulting from bronchial constriction.