Deck 14: Signal Transduction Mechanisms: Iimessengers and Receptors

Question 1

Which of the following statements is false with regard to G-protein coupled receptors (GPCRs)?

A)GPCRs can interact with specific receptor interacting proteins to modify ligand affinity.
B)Adenylate cyclase is activated.
C)Phosphodiesterase creates v cAMP molecules in response to moderate cAMP levels.
D)Protein Kinase A is activated by cAMP.
E)cAMP signals for its own degradation indirectly.

Answer 1

C

Question 2

Which of the following statements concerning the properties of ligands for intracellular receptor systems is correct?

A)Steroids are produced from cholesterol.
B)Changes in the composition of your diet can affect the concentration of some of these ligands in your body.
C)Some ligands are bound to specific proteins when carried in the blood.
D)both choices A and C
E)choices A, B, and C

Answer 2

E

Question 3

With regard to hormones,responses occurring over the shortest distance would be classified as

A)paracrine.
B)endocrine.
C)autocrine.
D)juxtacrine.
E)All of the above choices work over similar distances.

Answer 3

C

Question 4

It would be useful to determine if the mechanism of action for the XFFXFF receptor is similar to that of estrogen or epinephrine.To test this,you use a nonhydrolyzable analogue of GTP in the reaction mixture.If the mechanism is still similar to that of epinephrine,you would expect the cellular responses would be

A)blocked.
B)prolonged.
C)delayed.
D)both choices B and C
E)The mechanism cannot be determined.

Question 5

Which of the following is not a receptor tyrosine kinase?

A)EGF
B)PDGF
C)TGF
D)FGF

Question 6

IL-2 is a growth factor that acts on

A)embryonic cells.
B)T lymphocytes.
C)macrophages.
D)muscle cells.
E)epithelial cells.

Question 7

To have a hormone receptor system that is responsive to changes in hormone concentration,it is useful if the concentration of the hormone is

A)always more than 10 times the Kd.
B)never more than 10 times the Kd.
C)far below the Kd before the stimulation of hormone secretion.
D)far above the Kd before the stimulation of hormone secretion.
E)always constant.

Question 8

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

A)destruction of the ligand.
B)a lessened response to the ligand.
C)receptor down-regulation.
D)receptor-mediated endocytosis.
E)lowered affinity of a receptor for the ligand.

Question 9

Which of the following pairings is not correct?

A)adenylyl cyclase-ATP
B)phospholipase C-diacylglycerol (DAG)
C)phospholipase C-inositol triphosphate
D)calmodulin-calcium ions

Question 10

After determining which preparation contained the XFF receptor,you wish to determine the properties of the ligand receptor.Using a radioactive XFF,you wish to determine if the properties are similar to that of epinephrine and the epinephrine receptor.If so,you expect to find the radioactive XFF

A)within the cell.
B)associated with the ER.
C)on the cell surface.
D)associated with mitochondria.
E)in the nucleus.

Question 11

G protein-adenyl cyclase activity has been shown,in some cases,to be associated with certain diseases.In the case of cholera,which of the following is not correct?

A)Vibrio cholera bacteria colonize the gut.
B)Cholera toxin is secreted by Vibrio cholera bacteria.
C)The cholera toxin causes the cells of the gut to take in salts and fluids.
D)Cholera toxin alters Gs so that it no longer hydrolyzes GTP.
E)The toxin, by altering Gs, keeps intracellular cAMP levels high and doesn't allow them to decrease.

Question 12

You add a large amount of XFF to cultured liver cells.Which of the following might you observe if XFF can bind to human epinephrine receptors?

A)increased cell division
B)decreased protein synthesis
C)glycogen breakdown
D)glucose-6-phosphate polymerization
E)all of the above

Question 13

Hydrophobic messengers include which of the following?

A)retinoids
B)cAMP
C)pertussis toxin
D)calcium ions
E)ryanodine

Question 14

You argue with one of your fellow students that other features of the protein suggest that the protein is much like EGF.To discredit this,you would show the data obtained with

A)radioactive XFF.
B)binding assay.
C)use of nonhydrolyzable GTP analogues.
D)amino acid phosphorylation.
E)tyrosine kinase inhibition studies.

Question 15

Which of the following would be characterized as a juxtacrine signal?

A)contact-dependent
B)endocrine
C)self-responding
D)distal neighbors
E)both choices B and D

Question 16

When nitric oxide is used in the dilation of smooth muscle cells,which of the following would interfere with the relaxation of the smooth muscle cells? Inhibitors of

A)calcium release by the ER.
B)nitric oxide.
C)guanylyl cyclase.
D)calmodulin.
E)all of the above

Question 17

Which of the following ligands would not have an intracellular receptor?

A)cortisol
B)retinoic acid
C)thyroxine
D)epinephrine
E)progesterone

Question 18

You obtain two different preparations of XFF,one of which contains the receptors for XFF.You perform a binding assay and obtain a standard curve.Based upon this data,what value would reflect the affinity of the receptor for the ligand? (Assume a 1 XFF-to-1 receptor interaction.)

A)Kd
B)Bmax
C)Kd - Bmax
D)1/B_max
E)The affinity cannot be detertmined from the information available

Question 19

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

A)agonists.
B)receptor upregulators.
C)specific proteoglycans.
D)syndecans.
E)antagonists.

Question 20

All of the following are second messengers except

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

Question 21

All of the following are second messengers,except

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

Question 22

Which hormone is not an amino acid derivative?

A)histamine
B)norepinephrine
C)prostaglandin
D)epinephrine
E)thyroxine

Question 23

A developing organism's failure to produce muscle tissue is most likely due to

A)underdevelopment of the ectoderm.
B)underdevelopment of the endoderm.
C)fibroblast growth factor receptor mutations.
D)adenylate cyclase mutations.
E)missing chromosomes.

Question 24

The kinase central to second messenger signalling based cAMP is

A)protein kinase A.
B)ATPase.
C)Avastin kinase.
D)phosphorylase A.
E)RNase PH.

Question 25

Kinases and phosphatases are essential in the cell because they

A)help turn proteins "on and off" through changes in phosphorylation status.
B)are enzymes that destroy damaged proteins.
C)sense short poly-A tails in mRNA as a signal to degrade the mRNA.
D)destroy second messengers, thereby turning off a signal transduction pathway.
E)all of the above

Question 26

You are testing a drug that might be marketed as an anti-inflammatory agent.It would be a good choice if it possessed which of the following responses?

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

Question 27

You have recently identified a molecule that you believe to be a ligand associated with a signal transduction mechanism.All you know about this ligand is that chemically it is hydrophilic.As a result,you expect it to interact with its receptor

A)at the outer cell surface.
B)within the cytoplasm of the cell.
C)within the nucleus of the cell.
D)on the cytoplasmic side of the plasma membrane.
E)all of the above

Question 28

In designing a new drug that may interfere with G-protein coupled receptor interacting protein functions,one possible target for drug action is not

A)altering ligand affinity for the receptor.
B)promoting close association with other signal proteins.
C)modifying epinephrine production.
D)promoting receptor dimerization.
E)controlling receptor localization in the membrane.

Question 29

Phosphatases are enzymes that

A)add phosphate groups.
B)are always inhibitory.
C)do not alter target activity.
D)remove phosphate groups.
E)all of the above

Question 30

Which of the following are associated with the binding of numerous signaling molecules and regulating their responses in multi-enzyme complexes?

A)MAP kinase
B)14-3-3 proteins
C)growth factor complexes
D)alpha-factor
E) G-protein activating protein

Question 31

If one homogenizes liver cells,separates the membranes from the cytoplasm,and then adds epinephrine to only the cytoplasmic portion,

A)cAMP will be produced.
B)G-proteins will be activated.
C)adenylyl cyclase will be activated.
D)calcium ions will be released.
E)none of the above

Question 32

Which of the following statements regarding the Ras protein is false?

A)Ras is monomeric.
B)It is regulated by GTPase activating proteins.
C)The ligands are largely steroid hormones.
D)It is regulated by Sos, a guanine nucleotide exchange factor.
E)Ras activates a cascade of phosphorylation events.

Question 33

Prostaglandins are not

A)endocrine hormones.
B)important in smooth muscle function.
C)paracrine hormones.
D)stimulators of inflammation.
E)formed from arachidonic acid.

Question 34

Which of the following signalling proteins is specifically associated with development in animals?

A)Hedgehog
B)Zbtb7
C)Ryanodine
D)calcium-dependent protein phosphorylases
E)protein kinase A

Question 35

Kinases are enzymes that

A)add phosphate groups.
B)do not alter target activity.
C)are always inhibitory.
D)remove phosphate groups.
E)all of the above

Question 36

You wish to determine if cytosolic calcium fluxes are associated with signal transduction in a particular cell type.One means of observing the calcium fluxes would be to utilize

A)caspases.
B)cytochrome c.
C)nitric oxide.
D)radioactive cAMP.
E)cameleons.

Question 37

MAPKs are activated by

A)methylation.
B)microtubules.
C)membranes.
D)mitogens.
E)methionine.

Question 38

Which of the following is not a plant hormone?

A)brassinosteroids
B)ethylene
C)abscisic acid
D)auxin
E)allomone

Question 39

Blood pressure is regulated by the second messenger

A)cAMP.
B)Ca²⁺.
C)IP₃.
D)CO.
E)NO.

Question 40

IP₃ receptors are associated with

A)plasma membranes.
B)intracellular membranes.
C)mitochondrial membranes.
D)ER membranes.
E)lysosomes.

Question 41

Explain how caffeine,a methylxanthine,works to stimulate bronchodilation in asthma.

Question 42

________ produces the second messenger diacylglycerol (DAG).

Question 43

Compare and contrast cell signalling via receptor serine/threonine kinases and Ras.

Question 44

The key mediators of apoptosis are the ________.

Question 45

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

Question 46

The ultimate,coordinated response of cells to a vast array of signals from the environment is known as ________.

Question 47

In animal eggs,once fertilization occurs,________ are the second messengers that trigger egg activation.

Question 48

A type of programmed cell death associated with DNA fragmentation and caspases is known as ________.

Question 49

________ are genetically engineered proteins that allow cytosolic calcium fluxes to be observed by an increase in fluorescence.

Question 50

The Gα subunit is responsible for activation of ________.

Question 51

A strain of Drosophila known as dunce produces one-half the amount of cAMP phosphodiesterase than the wild type flies.Using your knowledge of cell signalling based upon cAMP,what effects would you expect in the dunce flies?

Question 52

________ nucleotides are common signals in animal cells but not in plant cells.

Question 53

In situations where signaling pathway components need to be "fixed" in a particular position within the cell (e.g.,in the yeast mating pathway),they are associated with ________.

Question 54

Design experiments that would allow you to independently detect each of the following: G-protein mediated signal transduction,nitric oxide signal transduction,and calcium ion fluxes.

Question 55

________ is the second messenger associated with the regulation of blood pressure.

Question 56

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

Question 57

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