Becker's World of the Cell, 8e (Hardin/Bertoni/Kleinsmith) Chapter 14 Signal Transduction Mechanisms: II. Messengers and Receptors Multiple Choice
... [Show More] Questions 1) 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 Answer: E 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: E 3) All of the following are second messengers except A) calcium ions. B) IP3. C) DAG. D) cameleons. E) PDGF. Answer: E 4) 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. Answer: C Contact: [email protected] 5) Hydrophobic messengers include which of the following? A) retinoids B) cAMP C) pertussis toxin D) calcium ions E) ryanodine Answer: A 6) 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. Answer: A 7) 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 Answer: A 8) IL-2 is a growth factor that acts on A) embryonic cells. B) T lymphocytes. C) macrophages. D) muscle cells. E) epithelial cells. Answer: B 9) Which of the following ligands would not have an intracellular receptor? A) cortisol B) retinoic acid C) thyroxine D) epinephrine E) progesterone Answer: D 10) Which of the following is not a receptor tyrosine kinase? A) EGF B) PDGF C) TGF D) FGF Answer: D Base your answers to the questions below on the following information: You have isolated a factor from the blood of a space alien and named it XFF (for X-files factor). Based on preliminary data, you think that XFF could be one of three compounds normally found in human blood: epidermal growth factor (EGF), epinephrine, or estrogen. 11) 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) Bmax 1 E) The affinity cannot be detertmined from the information available Answer: A 12) It would be useful to determine if the mechanism of action for the XFF XFF 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. Answer: B 13) 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 Answer: C 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. Answer: E 15) 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. Answer: C 16) 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. Answer: E 17) 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 Answer: A 18) 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: C 19) 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. Answer: C 20) 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: C 21) 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 Answer: C 22) 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. Answer: C 23) 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 Answer: A 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. Answer: A 25) 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. Answer: C 26) 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 Answer: A 27) Prostaglandins are not A) endocrine hormones. B) important in smooth muscle function. C) paracrine hormones. D) stimulators of inflammation. E) formed from arachidonic acid. Answer: A 28) 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 Answer: A 29) 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 Answer: A 30) Which of the following is not a plant hormone? A) brassinosteroids B) ethylene C) abscisic acid D) auxin E) allomone Answer: E 31) 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. Answer: E 32) 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 Answer: E 33) IP3 receptors are associated with A) plasma membranes. B) intracellular membranes. C) mitochondrial membranes. D) ER membranes. E) lysosomes. Answer: D 34) Blood pressure is regulated by the second messenger A) cAMP. B) Ca2+. C) IP3. D) CO. E) NO. Answer: E 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 Answer: A 36) 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 Answer: D 37) MAPKs are activated by A) methylation. B) microtubules. C) membranes. D) mitogens. E) methionine. Answer: D 38) Which hormone is not an amino acid derivative? A) histamine B) norepinephrine C) prostaglandin D) epinephrine E) thyroxine Answer: C 39) All of the following are second messengers, except A) cyclic adenosine monophosphate. B) inositol trisphosphate. C) diacylglycerol. D) epinephrine. E) calcium ions. Answer: D 40) 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. Answer: C Matching Questions Choose the item in column 2 that best matches each item in column 1. A) GDP B) stimulation of Gi C) endocrine hormones D) inhibition of Gi E) IP3 F) Ras G) calcium ions H) catalyzes formation of second messenger diacylglycerol (DAG) I) calmodulin J) GTP K) potassium ions L) thrombin M) catalyzes formation of cAMP from ATP N) paracrine hormones 1) phospholipase C 2) precursor of diacylglycerol 3) second messenger associated with prevention of penetration of an animal egg by multiple sperm cells 4) primary signal associated with platelet activation 5) protein that, when bound with calcium, can be a second messenger 6) hormones acting over long distances 7) monomeric G protein 8) adenylate cyclase 9) pertussis toxin 10) necessary for the activation of heterotrimeric G proteins Answers: 1) H 2) E 3) G 4) L 5) I 6) C 7) F 8) M 9) D 10) J Match the second messenger on the left with the properties on the right. A) activates protein kinase C B) opens sensory-associated ion channels C) can bind calmodulin D) glucose mobilization E) opens calcium channels 11) cAMP 12) IP3 13) DAG 14) calcium 15) cGMP Answers: 11) D 12) E 13) A 14) C 15) B Short Answer Questions 1) The α-subunit of a heterotrimeric G protein is active when bound to ________. Answer: GTP 2) EGF (epidermal growth factor) activates cell division by binding ________. Answer: receptor tyrosine kinases 3) In animal eggs, once fertilization occurs, ________ are the second messengers that trigger egg activation. Answer: calcium ions 4) ________ produces the second messenger diacylglycerol (DAG). Answer: Phospholipase C 5) In heterotrimeric G proteins, the ________ subunit stimulates adenylyl kinase. Answer: Gα; 6) ________ are genetically engineered proteins that allow cytosolic calcium fluxes to be observed by an increase in fluorescence. Answer: Cameleons 7) A type of programmed cell death associated with DNA fragmentation and caspases is known as ________. Answer: apoptosis 8) ________ is the second messenger associated with the regulation of blood pressure. Answer: Nitric oxide 9) The Gα subunit is responsible for activation of ________. Answer: adenylyl cyclase 10) ________ nucleotides are common signals in animal cells but not in plant cells. Answer: Cyclic 11) The ultimate, coordinated response of cells to a vast array of signals from the environment is known as ________. Answer: signal integration 12) 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 ________. Answer: scaffolding proteins. 13) The key mediators of apoptosis are the ________. Answer: caspases Inquiry 1) Design experiments that would allow you to independently detect each of the following: Gprotein mediated signal transduction, nitric oxide signal transduction, and calcium ion fluxes. Answer: A variety of valid answers could be obtained, and it is up to the instructor whether or not to accept the validity of the student answers. However, one could use nonhydrolyzable GTP analogs, mimicking of responses with treatment of cells with nitroglycerin, and cameleons as possible answers. 2) 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? Answer: Basically, the students need to discuss the fact that cAMP will remain longer in the cell, resulting in prolonged cAMP levels within the cell. 3) Explain how caffeine, a methylxanthine, works to stimulate bronchodilation in asthma. Answer: Caffeine and theophylline (commonly prescribed asthma drug) are both methylxanthines. Methylxanthines are cAMP phosphodiesterase inhibitors. As such, they prolong cAMP within cells and the subsequent maintenance of cAMP levels within the cells stimulates bronchodilation. 4) Compare and contrast cell signalling via receptor serine/threonine kinases and Ras. Answer: Receptor serine/threonine kinases act through receptor-regulated Smads and the accessory Smad4. Together, they enter the nucleus as a complex following receptor activation. Ras is regulated by GAPs and Sos (guanine-nucleotide exchange factor). This in turn activates a cascade of phosphorylation events, resulting in the activation of transcription factors that mediate gene expression. [Show Less]