Test Fileto accompany

Life: The Science of Biology, Ninth EditionSadava • Hillis • Heller • Berenbaum

Chapter 7: Cell Signaling and Communication

TEST FILE QUESTIONS(By Catherine Ueckert)

Multiple Choice

1. Which of the following statements about cell signaling in voles is false?a. A signal transduction pathway can bring about changes in behavior.b. Oxytocin and vasopressin are signals that induce bonding and caring behaviors in voles.c. Oxytocin acts as a signal for premating behaviors.d. The interaction of the receptor and the signal causes the receptor to change shape.e. Although oxytocin and vasopressin are widely circulated in the bloodstream, they only bind to a few cell types.Answer: cTextbook Reference: 7.0 Love signalsPage: 128Bloom’s Category: 2. Understanding

2. Which of the following statements is true?a. Eukaryotic, but not prokaryotic, cells process information from their environment.b. Prokaryotic, but not eukaryotic, cells process information from their environment.c. The mere presence of a signal will cause a cell to respond to it.d. Light can be a signal.e. Sense organs allow cells to respond to physical signals but not chemical signals.Answer: dTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 129Bloom’s Category: 2. Understanding

3. To respond to a signal, a cell must have a(n) _______ molecule that can detect the signal.a. paracrineb. receptorc. autocrined. respondere. All of the aboveAnswer: b

Textbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 129Bloom’s Category: 2. Understanding

4. Which of the following statements is false?a. Plants respond to light as a signal.b. The environment experienced by a cell deep inside a large multicellular organism is very different from the external environment.c. Some plants are capable of responding to temperature fluctuations.d. Some cells can self-stimulate cell division by making their own division signals.e. None of the aboveAnswer: eTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 129Bloom’s Category: 2. Understanding

5. Most of the chemical signals coming to a cell deep inside a multicellular organism come froma. the external environment.b. the lymphatic system.c. other cells.d. the nervous system.e. None of the aboveAnswer: cTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 129Bloom’s Category: 2. Understanding

6. The first component of a signal transduction pathway is a(n)a. paracrine molecule.b. responder.c. receptor.d. hormone.e. effector molecule.Answer: cTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 129Bloom’s Category: 2. Understanding

7. Signals reach target cells in multicellular organisms via _______ and _______.a. circulation; diffusionb. conduction; diffusionc. circulation; perspirationd. chaperon trafficking; transmembrane transporte. cytoskeletal trafficking; perfusionAnswer: a

Textbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 129Bloom’s Category: 2. Understanding

8. Cells receive which of the following signals?a. Lightb. Soundc. Odorantsd. Hormonese. All of the aboveAnswer: eTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 129–130Bloom’s Category: 1. Remembering

9. The signals that bind to receptors of the same cell that made them are known asa. paracrine signals.b. parasitic signals.c. autocrine signals.d. hormones.e. responders.Answer: cTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 130Bloom’s Category: 1. Remembering

10. The signals that bind to receptors on nearby cells are known asa. paracrine signals.b. parasitic signals.c. autocrine signals.d. hormones.e. responders.Answer: aTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 130Bloom’s Category: 1. Remembering

11. Signals that travel to distant cells through the circulatory system are known asa. paracrine signals.b. parasitic signals.c. autocrine signals.d. hormones.e. responders.Answer: dTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 130

Bloom’s Category: 1. Remembering

12. Which of the following is most likely to involve the circulatory system?a. Paracrine signalsb. Parasitic signalsc. Autocrine signalsd. Hormonese. RespondersAnswer: dTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 130Bloom’s Category: 2. Understanding

13. The transmembrane protein EnvZ in a signal transduction pathway found in E. coli is an example of a(n)a. autocrine molecule.b. transductor.c. responder.d. hormone.e. None of the aboveAnswer: eTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 131Bloom’s Category: 4. Analyzing

14. In the E. coli signal transduction pathway, changes in the aqueous media cause part of the receptor to undergo a change ina. responder.b. conformation.c. hormonal activity.d. amplification.e. extracellular environment.Answer: bTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 131Bloom’s Category: 2. Understanding

15. The conformational change in EnvZ causes it to become a(n)a. autocrine receptor.b. responder.c. ligand.d. protein kinase.e. phosphate group.Answer: dTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 131

Bloom’s Category: 2. Understanding

16. Which of the following is true about EnvZ?a. It phosphorylates itself during signal transduction.b. It has domains on both the inside and the outside of the cell.c. It acts as a responder.d. Both a and be. All of the aboveAnswer: dTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 131Bloom’s Category: 4. Analyzing

17. The second component of a signal transduction pathway is known as aa. receptor.b. hormone.c. responder.d. transducer.e. None of the aboveAnswer: cTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 132Bloom’s Category: 2. Understanding

18. In general, all cell signaling causesa. increased expression of genes.b. an influx of ions.c. protein kinase activity.d. G protein activation.e. a change in receptor conformation.Answer: eTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 132Bloom’s Category: 2. Understanding

19. In order, from start to finish, the basic steps of a signal transduction pathway area. signal, responder, receptor, effects.b. receptor, signal, responder, effects.c. signal, receptor, responder, effects.d. signal, receiver, responder, effects.e. None of the aboveAnswer: cTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 132Bloom’s Category: 4. Analyzing

20. In the E. coli signal transduction pathway, which of the following protein molecules acts as the responder?a. OmpRb. EnvZc. SORpd. Autocrinee. None of the aboveAnswer: aTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 132Bloom’s Category: 2. Understanding

21. The phosphorylation and change in shape of the responder in the E. coli signaling transduction pathway is a key event in signaling for which of the following reasons?a. The signal that originally was on the outside of the cell has been transduced to a protein that exists totally within the cell’s cytoplasm.b. The signal has been amplified.c. The altered responder can bind to DNA and stimulate transcription of one or more genes.d. Both a and ce. All of the aboveAnswer: eTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 132Bloom’s Category: 4. Analyzing

22. In the E. coli signaling transduction pathway, which of the following is true about the OmpR protein?a. When phosphorylated, it acts as a transcription factor for OmpC.b. It exists both inside and outside the cell membrane.c. It is a receptor.d. Both a and be. All of the aboveAnswer: aTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 132Bloom’s Category: 4. Analyzing

23. In the E. coli signaling transduction pathway, which of the following is true about OmpC?a. It is a transcription factor.b. It can insert itself into the outer membrane, resulting in the eventual restoration of homeostasis.c. It phosphorylates other proteins.d. It is a receptor.e. None of the above

Answer: bTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 132Bloom’s Category: 4. Analyzing

24. Which of the following is false?a. Cells are bombarded with numerous signals, but they respond to only a few.b. A cell’s receptors determine whether or not the cell will respond to a signal.c. Receptor proteins are very specific.d. There are only a few kinds of signal receptor proteins.e. None of the aboveAnswer: dTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 132Bloom’s Category: 2. Understanding

25. A molecule that binds to the particular three-dimensional structure of another molecule’s receptor site is known as a(n)a. responder.b. receptor.c. ligand.d. ion channel.e. filament.Answer: cTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 132Bloom’s Category: 1. Remembering

26. In what way do ligand–receptor interactions differ from enzyme–substrate reactions?a. The ligand signal is not usually metabolized into useful products.b. Receptor–ligand interactions do not obey the laws of mass action.c. Inhibitors never bind to the ligand-binding site.d. Reversibility never occurs in the ligand–receptor interaction.e. The enzyme–substrate reaction and the ligand–receptor interaction do not differ.Answer: aTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 132Bloom’s Category: 2. Understanding

27. Which of the following is true?a. For most ligand–receptor complexes, binding is favored.b. Ligand–receptor interactions are reversible.c. Many drugs that alter human behavior prevent binding of receptors’ specific ligands.d. Both a and be. All of the aboveAnswer: e

Textbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 132–133Bloom’s Category: 4. Analyzing

28. Caffeine mimics the molecular structure ofa. paracrine.b. aspirin.c. adenosine.d. autocrine.e. None of the aboveAnswer: cTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 133Bloom’s Category: 2. Understanding

29. Signal molecules can be divided into two general classes according to their receptors. What are these two kinds of receptors?a. Plasma membrane and ion channelb. Plasma membrane and protein kinasec. Ion channel and protein kinased. G protein-linked and protein kinasee. None of the aboveAnswer: eTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 133Bloom’s Category: 2. Understanding

30. The receptor of estrogena. is an ion channel receptor.b. is a protein kinase receptor.c. exists within the plasma membrane.d. exists within the cytoplasm.e. None of the aboveAnswer: dTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 133Bloom’s Category: 2. Understanding

31. Vitamin A is a relatively small, lipid-soluble molecule that can behave as a hormone. Its receptora. is an ion channel receptor.b. is a protein kinase receptor.c. involves a G protein.d. is not connected to the plasma membrane.e. does not exist; vitamin A does not have a receptor.Answer: d

Textbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 133Bloom’s Category: 4. Analyzing

32. Which of the following molecules has an ion channel receptor?a. Insulinb. Estrogenc. Acetylcholined. Lithiume. None of the aboveAnswer: cTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 134Bloom’s Category: 1. Remembering

33. Which of the following is true about acetylcholine?a. It binds to a sodium channel receptor.b. It acts as a neurotransmitter.c. The binding of two molecules of acetylcholine to a receptor are required to open the channel.d. It moves against the concentration gradient.e. All of the aboveAnswer: eTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 134Bloom’s Category: 2. Understanding

34. Which of the following strongly binds to the acetylcholine receptor?a. Estrogenb. Acetylcholinec. Sodiumd. OmpCe. Protein kinasesAnswer: bTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 134Bloom’s Category: 1. Remembering

35. Which of the following molecules has a protein kinase receptor?a. Insulinb. Estrogenc. Acetylcholined. Sodiume. G proteinsAnswer: aTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?

Page: 134Bloom’s Category: 2. Understanding

36. Which of the following statements about the insulin receptor is false?a. It autophosphorylates.b. It requires binding by two insulin molecules to be activated.c. It catalyzes the phosphorylation of insulin response substrates.d. It is located entirely within the cytoplasm.e. None of the aboveAnswer: dTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 134Bloom’s Category: 2. Understanding

37. After the GTP-bound subunit of the G protein separates from the rest of the G protein, it travels until it encountersa. an activator.b. a receptor.c. an effector protein.d. a protein kinase.e. another G protein.Answer: cTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 134Bloom’s Category: 2. Understanding

38. For a G protein to play its part in moving events forward in a signal pathway,a. GDP must be released, and a GTP must occupy the nucleotide-binding site.b. GTP must be released, and a GDP must occupy the nucleotide-binding site.c. cGMP must occupy the otherwise empty nucleotide-binding site.d. cGMP must leave the otherwise occupied nucleotide-binding site.e. None of the aboveAnswer: aTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 134Bloom’s Category: 2. Understanding

39. Which of the following statements is true?a. G proteins contain only one important binding site.b. When a G protein binds to an activated receptor protein, ADP is exchanged for ATP.c. G protein receptors are single proteins that have seven distinct regions that pass through the phospholipid bilayer of the cell membrane.d. G proteins can only activate effector proteins; they cannot inhibit them.e. None of the aboveAnswer: cTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?

Page: 134–135Bloom’s Category: 2. Understanding

40. If a G protein were unable to release its bound nucleotide but could hydrolyze it, signal transduction woulda. cease.b. be continuous.c. be unaffected.d. be constantly switching on and off.e. be unpredictable.Answer: aTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 135Bloom’s Category: 3. Applying

41. If a G protein were able to release its bound nucleotide but not to hydrolyze it, signal transduction woulda. cease.b. be continuous.c. be unaffected.d. be constantly switching on and off.e. be unpredictable.Answer: bTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 135Bloom’s Category: 3. Applying

42. Which of the following would likely not be observed in a person injected with epinephrine?a. Contraction of muscles surrounding the blood vessels that line the digestive tractb. Increased activity of heart musclec. Increased glucose mobilizationd. Activation of G proteinse. All of the above would occur.Answer: aTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 135Bloom’s Category: 4. Analyzing

43. Which of the following is true?a. Direct transduction is more common than indirect transduction.b. In indirect transduction, second messengers mediate the interaction between the receptor and the cell’s response.c. Amplification never occurs via second messengers.d. Indirect transduction occurs at the plasma membrane.e. All of the above

Answer: bTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 136Bloom’s Category: 2. Understanding

44. What is the G protein that has been found in many human bladder cancers?a. Acetylcholineb. Rapc. Rasd. Ratse. None of the aboveAnswer: cTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 136Bloom’s Category: 1. Remembering

45. Which of the following is true about the abnormal form of Ras found in bladder cancer cells?a. Because it is inactive, it is unable to inhibit growth factors.b. It is always active because it is continuously bound to GTP.c. If it were inhibited, cells would continue to divide.d. It acts as an ion channel receptor.e. It stimulates epinephrine.Answer: bTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 136Bloom’s Category: 1. Remembering

46. A benefit of the many steps involved in protein kinase cascades is that they allow fora. some specificity of the response.b. amplification of the signal.c. information to be communicated to the nucleus.d. variation in the response.e. All of the aboveAnswer: eTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 137Bloom’s Category: 2. Understanding

47. How does a protein kinase cascade amplify an intercellular signal?a. Protein kinase opens cell junctions, amplifying the intercellular signal.b. The activated G protein binds and activates a second protein, amplifying the signal.c. Nitric oxide opens cell channels, which allows protein kinase molecules to move quickly from cell to cell.d. Second messengers create shortcuts that create multiple cascades.

e. One activated receptor kinase molecule can trigger the activation of thousands of proteins.Answer: eTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 137Bloom’s Category: 4. Analyzing

48. During what part of the signal transduction pathway is Ras activated?a. Early in the pathwayb. Around the midpointc. Late in the pathwayd. All along the pathwaye. None of the aboveAnswer: aTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 137Bloom’s Category: 2. Understanding

49. Which molecule acts as a second messenger in the cascade by which epinephrine stimulates the activation of the enzyme glycogen phosphorylase?a. Adenosineb. Caffeinec. Citric acidd. Cyclic AMPe. Adenylyl cyclaseAnswer: dTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 138Bloom’s Category: 2. Understanding

50. Second messengersa. are typically very specific in their activity.b. do not amplify a signal.c. have enzymatic activity.d. can be derived from lipids.e. All of the aboveAnswer: dTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 138Bloom’s Category: 2. Understanding

51. Which of the following statements about cyclic AMP is false?a. It can bind to, and thus open, ion channels in some sensory cells.b. In some circumstances it can bind to a protein kinase in the cytoplasm.c. The enzyme adenylyl cyclase catalyzes its formation from ATP.d. It is a second messenger.

e. It has enzymatic activity.Answer: eTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 138Bloom’s Category: 2. Understanding

52. Which of the following statements is false?a. Diacylglycerol can act as a second messenger.b. Inositol triphosphate can act as a second messenger.c. Protein kinase C can phosphorylate a wide variety of proteins.d. Inositol triphosphate remains bound to the membrane after phospholipase C catalyzes its formation.e. Inositol triphosphate can open an ion channel, releasing calcium into the cytoplasm.Answer: dTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 138Bloom’s Category: 2. Understanding

53. The concentration of cAMP in a cell is increased bya. phosphodiesterase.b. cGMP.c. a protein kinase.d. a second messenger.e. a G protein.Answer: eTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 138–139Bloom’s Category: 2. Understanding

54. The hydrolysis of PIP2 results ina. inositol triphosphate and diacylglycerol.b. inositol triphosphate and cyclic AMP.c. two second messengers.d. Both a and ce. Both b and cAnswer: dTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 139Bloom’s Category: 2. Understanding

55. IP3 is released into the cytoplasm when PIP2 is hydrolyzed. IP3

a. opens Ca2+ channels.b. closes Ca2+ channels.c. stimulates G protein activation of phospholipase C.d. activates cyclic AMP.e. produces calcium-binding protein S4.

Answer: aTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 139Bloom’s Category: 2. Understanding

56. Lithium can be effective in the treatment of bipolar disorder because ita. opens up the lithium ion channel.b. acts as a second messenger accelerating the IP3/DAG signal transduction pathway.c. inhibits G protein activation of phospholipase C and inhibits synthesis of IP3.d. changes the osmotic balance of cells.e. acts as a neurotransmitter.Answer: cTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 140Bloom’s Category: 2. Understanding

57. Which of the following statements about calcium is true?a. Calcium ions are more concentrated inside than outside the cell.b. Active transport maintains the concentration difference of calcium ions.c. A cell can increase intracellular concentrations of calcium by making more calcium.d. IP3 is the only signal that causes calcium channels to open.e. It inhibits cell division in fertilized eggs.Answer: bTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 140Bloom’s Category: 2. Understanding

58. Which of the following statements is false?a. Calcium ions can stimulate their own release from intracellular stores.b. The opening of calcium channels takes place relatively slowly, from seconds to minutes.c. Calcium ions can act as second messengers.d. The entry of a sperm into an egg causes a massive opening of calcium channels.e. Increases in calcium can result in the activation of protein kinase C.Answer: bTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 140Bloom’s Category: 4. Analyzing

59. Viagra, used to treat erectile dysfunction, acts by means of the release of the second messengera. cyclic AMP.b. calcium ion.c. nitric oxide.d. calmodulin.e. acetylcholine.

Answer: cTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 140Bloom’s Category: 2. Understanding

60. Which of the following about nitric oxide is true?a. Because it is chemically stable, it is able to travel relatively long distances.b. It does not diffuse readily.c. It is released by nitroglycerin, resulting in the relaxation of blood vessels.d. Calcium ions inhibit the enzyme that catalyzes nitric oxide.e. All of the aboveAnswer: cTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 140Bloom’s Category: 2. Understanding

61. Increased synthesis of phosphodiesterase would lead toa. decreased concentration of cyclic AMP.b. increased concentration of cyclic AMP.c. increased concentration of calmodium.d. decreased concentration of calmodium.e. inhibition of adenylyl cyclase.Answer: aTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 141Bloom’s Category: 3. Applying

62. Which of the following statements is true?a. Some mammals have over 1,000 genes for odor signal receptors.b. The signal transduction pathway triggered by odorant molecules results in the opening of ion channels.c. Each of the thousands of neurons in the nose expresses one of the odor signal receptors.d. Odorant receptors are G protein-linked.e. All of the aboveAnswer: eTextbook Reference: 7.4 How Do Cells Change in Response to Signals?Page: 142Bloom’s Category: 2. Understanding

63. Which of the following is not involved in the signaling cascade after the odorant molecule binds to its receptor?a. Activation of a G proteinb. Cyclic AMP used as a second messengerc. Nitric oxide used as second messengerd. Gated opening of ion channels

e. All of the above are involved in the signaling cascade.Answer: cTextbook Reference: 7.4 How Do Cells Change in Response to Signals?Page: 143Bloom’s Category: 2. Understanding

64. Which of the following represents the correct ordering of the molecules that are activated by a single molecule of epinephrine, from highest number of molecules to lowest number of molecules?a. cAMP, protein kinase A, phosphorylase kinase, glycogen phosphorylaseb. Glycogen phosphorylase, phosphorylase kinase, protein kinase A, cAMPc. cAMP, phosphorylase kinase, glycogen phosphorylase, protein kinase Ad. Glycogen phosphorylase, cAMP, protein kinase A, phosphorylase kinasee. Phosphorylase kinase, glycogen phosphorylase, cAMP, protein kinase AAnswer: bTextbook Reference: 7.4 How Do Cells Change in Response to Signals?Page: 143Bloom’s Category: 4. Analyzing

65. The G protein-mediated cascade stimulated by epinephrine results in the phosphorylation of two key enzymes. The eventual results of this phosphorylation are the _______ of glycogen synthase and the _______ of glycogen phosphorylase.a. stimulation; stimulationb. stimulation; inhibitionc. inhibition; stimulationd. inhibition; inhibitione. inhibition; introversionAnswer: cTextbook Reference: 7.4 How Do Cells Change in Response to Signals?Page: 143Bloom’s Category: 2. Understanding

66. Which of the following statements about gap junctions is true?a. They generally occupy less than 5 percent of the area of the plasma membrane.b. They are specialized structures that permit metabolic cooperation among the linked cells.c. They occur only in plants.d. They are made of G proteins.e. All of the aboveAnswer: bTextbook Reference: 7.5 How Do Cells Communicate Directly?Page: 144Bloom’s Category: 2. Understanding

67. Which of the following statements is true?a. Most cells are in contact with their neighbors.

b. Tight junctions are specialized for intercellular communication.c. Desmosomes are specialized for intercellular communication.d. Gap junctions are channels between adjacent cells.e. All of the aboveAnswer: aTextbook Reference: 7.5 How Do Cells Communicate Directly?Page: 144Bloom’s Category: 2. Understanding

68. Which of the following are specialized cell junctions that allow neighboring cells to communicate directly?a. Tight junctionsb. Gap junctionsc. Desmosomesd. Ion channelse. G proteinsAnswer: bTextbook Reference: 7.5 How Do Cells Communicate Directly?Page: 144Bloom’s Category: 1. Remembering

69. Gap junctions transverse the gap between plasma membranes of two cells by means ofa. plasmodesmata.b. desmosomes.c. connexons.d. cyclic AMP.e. direct transduction.Answer: cTextbook Reference: 7.5 How Do Cells Communicate Directly?Page: 144Bloom’s Category: 2. Understanding

70. In gap junctions, the channel pores permit the transport ofa. small signal molecules.b. ions.c. proteins.d. Both a and be. All of the aboveAnswer: dTextbook Reference: 7.5 How Do Cells Communicate Directly?Page: 144–145Bloom’s Category: 1. Remembering

71. Which of the following statements about plasmodesmata is false?a. Plasmodesmata are lined by the fused membranes themselves.

b. Plasmodesmata are larger than a gap junction channel.c. The desmotubule is probably derived from the endoplasmic reticulum.d. Only small metabolites and ions can move between plant cells.e. Plasmodesmata are specialized for intercellular communication.Answer: eTextbook Reference: 7.5 How Do Cells Communicate Directly?Page: 144–145Bloom’s Category: 2. Understanding

72. The membrane-lined bridges spanning the cell walls between plant cells are known asa. gap junctions.b. tight junctions.c. plasmodia.d. plasmodesmata.e. G protein receptors.Answer: dTextbook Reference: 7.5 How Do Cells Communicate Directly?Page: 145Bloom’s Category: 1. Remembering

73. Which of the following is a similarity of animal and plant cells?a. The connections between cells in both are lined by the fused plasma membranes themselves.b. The space available for diffusion is about the same in both.c. Both have tiny circulatory vessels (capillaries) to bring gases and nutrients to every cell.d. All of the abovee. None of the aboveAnswer: bTextbook Reference: 7.5 How Do Cells Communicate Directly?Page: 145Bloom’s Category: 4. Analyzing

74. Which of the following statements about plasmodesmata is true?a. They are not merely passive channels, but can be regulated.b. They are derived from integral proteins from adjacent plasma membranes.c. Their diameter is much smaller than that of a gap junction.d. Large proteins can move between plant cells because of them.e. All of the aboveAnswer: aTextbook Reference: 7.5 How Do Cells Communicate Directly?Page: 145Bloom’s Category: 2. Understanding

75. Which structure narrows the opening of the plasmodesma?a. A gap junction

b. Connexonsc. A desmotubuled. A ligande. A protein kinaseAnswer: cTextbook Reference: 7.5 How Do Cells Communicate Directly?Page: 145Bloom’s Category: 1. Remembering

Fill in the Blank

1. _______ and _______ are two signals that induce bonding and caring behaviors in voles.Answer: Oxytocin; vasopressinTextbook Reference: 7.0 Love signalsPage: 128–129Bloom’s Category: 1. Remembering

2. To respond to a signal, a cell must have a specific _______ that can detect the signal.Answer: receptorTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 129Bloom’s Category: 1. Remembering

3. Signals that diffuse to and affect nearby cells are known as _______ signals.Answer: paracrineTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 130Bloom’s Category: 1. Remembering

4. Usually transported via the circulatory system, _______ are signals sent to distant cells.Answer: hormonesTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 130Bloom’s Category: 1. Remembering

5. The entire signaling process is known as the signal _______ pathway. Its first component is called the _______, and its second component is known as the _______.Answer: transduction; receptor; responderTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 131–132Bloom’s Category: 1. Remembering

6. Phosphorylated OmpR is a(n) _______ factor; by binding to the promoter of OmpC, it changes the expression of the latter gene.

Answer: transcriptionTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 132Bloom’s Category: 2. Understanding

7. Phosphorylation changes the _______ and _______ of a protein.Answer: shape; functionTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 132Bloom’s Category: 2. Understanding

8. A molecule that binds to a receptor site in another molecule is known as a(n) _______.Answer: ligandTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 132Bloom’s Category: 1. Remembering

9. Caffeine restores wakefulness because it binds to receptors for _______, thus preventing this chemical from causing drowsiness.Answer: adenosineTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 133Bloom’s Category: 2. Understanding

10. Caffeine indirectly stimulates the signaling pathway associated with the “fight-or-flight” response normally stimulated by _______.Answer: epinephrine (or adrenaline)Textbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 133Bloom’s Category: 1. Remembering

11. Located inside the cell, _______ receptors bind to signals that can diffuse across the plasma membrane.Answer: cytoplasmicTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 133Bloom’s Category: 1. Remembering

12. When _______ (number) molecules of acetylcholine bind to its receptor, the ion channel opens briefly, allowing sodium ions to rush into the cell.Answer: twoTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 134Bloom’s Category: 1. Remembering

13. When activated, some receptor proteins catalyze the transfer of a(n) _______ group from ATP to a specific protein. Such receptor proteins are known as protein _______.Answer: phosphate; kinasesTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 134Bloom’s Category: 2. Understanding

14. Signaling proteins that are characterized by their ability to bind GTP and GDP are known as _______ proteins.Answer: GTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 134Bloom’s Category: 1. Remembering

15. In _______ transduction, the more common mode of transduction, another molecule, known as a(n) _______ mediates further interaction between the receptor and the response of the cell.Answer: indirect; second messengerTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 136Bloom’s Category: 2. Understanding

16. A protein found in abnormal form in many human bladder cancer cells, _______, is a G protein.Answer: RasTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 136Bloom’s Category: 1. Remembering

17. _______ is a second messenger found in the pathway by which epinephrine activates the liver enzyme that breaks down glycogen.Answer: Cyclic AMP (cAMP)Textbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 138Bloom’s Category: 1. Remembering

18. The enzyme phospholipase C breaks down PIP2 into two molecules, _______ and _______, both of which can function as second messengers.Answer: diacylglycerol (DAG); inositol triphosphate (IP3)Textbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 139Bloom’s Category: 2. Understanding

19. Used to treat bipolar disorder, _______ acts by inhibiting the G protein activation of phospholipase C.Answer: lithium

Textbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 139–140Bloom’s Category: 2. Understanding

20. The entry of a sperm into an egg causes a massive opening of _______ channels.Answer: calciumTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 140Bloom’s Category: 1. Remembering

21. The second messenger involved in the therapeutic use of Viagra is _______.Answer: nitric oxide (NO)Textbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 140–141Bloom’s Category: 1. Remembering

22. The binding of a single molecule of epinephrine to a receptor can result in the activation of 1,000 molecules of glycogen phosphorylase. This result of the signaling transduction cascade is an example of the phenomenon known as _______.Answer: amplificationTextbook Reference: 7.4 How Do Cells Change in Response to Signals?Page: 143Bloom’s Category: 2. Understanding

23. The plasmodesma is partially filled with a tubule called the _______.Answer: desmotubuleTextbook Reference: 7.5 How Do Cells Communicate Directly?Page: 144Bloom’s Category: 1. Remembering

24. Channels that permit metabolic cooperation among adjacent animal cells are known as _______.Answer: gap junctionsTextbook Reference: 7.5 How Do Cells Communicate Directly?Page: 144Bloom’s Category: 1. Remembering

Diagram

1. Label each of the four steps (Effects, Receptor, Responder, Signal) in the diagram below.

Answer: 1. Signal, 2. Receptor, 3. Responder, 4. EffectsTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 131Bloom’s Category: 1. Remembering

2. Draw what would happen when a hormone binds to a receptor, as shown in the diagram below.

Answer:

Textbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 135Bloom’s Category: 3. Applying

3. In the diagram below, where and how would lithium interact with the pathway?

Answer:

Lithium would inhibit the G protein activation of phospholipase C and the generation of IP3.Textbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 139Bloom’s Category: 3. Applying

STUDY GUIDE QUESTIONS(By Ed Dzialowski)

Knowledge and Synthesis

1. Which of the following does not occur during signal transduction?a. Binding of ligand to receptorb. Conformational change to the receptor proteinc. Conformational change of the signald. Alteration of cellular activitye. Conformational change in the ligandAnswer: cFeedback: In order for signal transduction to take place, the ligand must bind to the receptor, the receptor must undergo a conformational change, and the activity of the cell must be altered.Textbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 130–132

2. E. coli cells respond to osmotic changes by a. changing the permeability of the membrane.b. changing the DNA that is transcribed.c. phosphorylating OmpR.d. binding the ligand to EnvZ.e. increasing metabolism.Answer: aFeedback: The ultimate goal of any signaling pathway is an alteration in the function of the cell in response to the signal.Textbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 131

3. What do G protein-linked receptors and protein kinases have in common?a. Ligand bindingb. Conformational change once the ligand is boundc. Amplification of the signald. All of the abovee. None of the aboveAnswer: dFeedback: All types of receptors bind ligands, undergo conformational change, and amplify the signal.Textbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 135–136

4. Signal binding to a receptor differs from enzyme–substrate binding in thata. in signal binding the signal is not altered during the process.b. the single-binding process is reversible.c. in signal binding, cell receptors can become saturated by signal molecules.d. signal binding can be inhibited by an antagonist.e. None of the aboveAnswer: a

Feedback: Substrates are altered in enzyme–substrate complexes. Signals are not altered when they bind to receptors.Textbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 132

5. Which of the following statements about secondary messengers is true?a. They amplify the signal.b. They bind to the active site of the receptor.c. They result in multiple effects from a single signal.d. Both a and ce. All of the aboveAnswer: dFeedback: Secondary messengers both amplify the signal and have multiple effects within a cell.Textbook Reference: 7.3 How Is a Response to a Signal Transduced through the Cell?Page: 137–139

6. Caffeine is a stimulant that works because it acts as a(n) _______ to the adenosine receptors in a person’s brain, and stimulates _______ in that person’s heart and liver that increases blood flow and blood glucose.a. effector; a pathwayb. inhibitor; a cascade pathwayc. inhibitor; a ligandd. signal; inhibitorse. pathway; a ligandAnswer: bFeedback: Caffeine and adenosine bind to the same receptor protein. The binding of caffeine prevents adenosine from binding in the brain. In other organs, a series of cascades begin in response to caffeine binding.Textbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 133

7. Cytoplasmic receptors binda. small signals that can diffuse through the plasma membrane.b. secondary messengers, such as cAMP.c. hydrophilic molecules.d. ligands.e. All of the aboveAnswer: aFeedback: To bind to a cytoplasmic receptor, the ligand must be able to pass through the plasma membrane.Textbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 135

8. Which of the following statements about protein kinase cascades is true?a. Amplification can occur at each step in the path.

b. Information at the plasma membrane is communicated to the nucleus.c. The multiple steps allow for specificity of the process.d. Different targets can produce variation in the cellular response.e. All of the aboveAnswer: eFeedback: Amplification, regulation, specificity, and variation are all roles of protein kinase cascades.Textbook Reference: 7.3 How Is a Response to a Signal Transduced through the Cell?Page: 136–137

9. Which of the following is not part of the IP3 / DAG pathway?a. The binding of a hormone to a receptorb. The production of IP3 by a G proteinc. Activation of phospholipase Cd. The opening of Ca2+ channelse. All of the above are part of the pathway.Answer: bFeedback: IP3 and DAG are made when phospholipase C hydrolyzes PIP2.Textbook Reference: 7.3 How Is a Response to a Signal Transduced through the Cell?Page: 139

10. Which of the following statements about receptors is true?a. Receptors are only found on the surface of cells.b. Receptors are specific to the signal ligand.c. Most receptors can bind with many signal ligands.d. All receptors can act as ion channels.e. All of the aboveAnswer: bFeedback: Receptors interact only with specific ligands to bring about a response in the cell.Textbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 132–134

11. Gap junctions and plasmodesmata differ in thata. gap junctions are connected by protein tubules called connexons, whereas plasmodesmata are connected by extensions of the plant’s plasma membrane.b. gap junctions allow much larger molecules to pass through them.c. gap junctions have no real physical connection but are rather the space between adjacent cell membranes.d. one is of animal origin and the other is of plant origin.e. gap junctions are connected by desmotubules and plasmodesmata are connected by connexons.Answer: aFeedback: Both plasmodesmata and gap junctions provide physical connections between the cytoplasms of adjacent cells.Textbook Reference: 7.5 How Do Cells Communicate Directly?

Page: 144–145

12. Paracrine signalsa. act on the cells that made them.b. move through the blood and act on cells far from their source.c. act on cells that are near to those that secrete them.d. do not act through receptors.e. require large concentrations of the signaling molecule to function.Answer: cFeedback: Autocrine signals affect the cells that make them and paracrine cells affect nearby cells. A receptor in the plasma membrane binds hydrophilic signals.Textbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 130

13. Which of the following signals results in the direct activation of an enzyme?a. Acetylcholine binding to its receptorb. Insulin binding to its receptorc. Cortisol binding to its receptord. Fertilization of an egg by a sperm celle. All of the aboveAnswer: bFeedback: Insulin binds and activates a protein kinase receptor. Acetylcholine leads to a channel opening, cortisol binds to a cytoplasmic receptor and activates transcription, and fertilization leads to an increase in intracellular calcium concentrations. Textbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 133–135

14. Which of the following represents the correct order of signal transduction?a. Binding of signal, release of secondary messenger, alteration of receptor conformation, alteration of cellular functionb. Binding of signal, release of secondary messenger, alteration of receptor conformation, transcription of genec. Binding of signal, activation of target protein by responder, alteration of receptor conformation, release of secondary messenger; transcription of gened. Binding of signal, alteration of receptor conformation, alteration of cellular function, release of second messengere. Binding of signal, alteration of receptor conformation, activation of target protein by responder, alteration of cellular functionAnswer: eFeedback: Signals must bind their receptors, the conformation of the receptor is altered, a responder activates a target protein, and cell function changes.Textbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 130–132

15. Which of the following is not a response to a signal binding its receptor?a. A channel opening

b. A G protein’s exchange of GDP for GTPc. Increase in intracellular concentration of nitrous oxided. The diffusion of solutes through the porous outer membrane of E. colie. Activation of a protein kinaseAnswer: dFeedback: The diffusion of solutes through the porous outer membrane of E. coli is a signal; the other answer options are responses to signals.Textbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response? 7.3 How Is a Response to a Signal Transduced through the Cell?Page: 133–136, 140

Application

1. Based on your knowledge of prokaryotic and eukaryotic cell structure and function, explain how signal transduction might differ in prokaryotes and eukaryotes?Answer: Signal transduction in prokaryotes is limited to only one cell; there is no nuclear membrane to cross, and cascades tend to be simpler, with fewer intermediate steps.Textbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 130–131

2. Describe how protein kinases and G protein-linked receptors may interact in a signal transduction cascade.Answer: G protein-linked receptors frequently expose the protein kinase activities of effector molecules.Textbook Reference: 7.3 How Is a Response to a Signal Transduced through the Cell?Page: 136–137

3. Discuss the role of secondary messengers in a signaling pathway. How are they different from signals and receptors? What roles do secondary messenger and signals have in common?Answer: Secondary messengers function to amplify and spread signals. They do not bind to receptors and do not act like signals in the cascade. Signals result in a change in cell function; secondary messengers are part of the pathway that results in the change in cell function.Textbook Reference: 7.3 How Is a Response to a Signal Transduced through the Cell?Page: 137–138

4. Can a receptor act as a signal? Explain your answer.Answer: A receptor can act as a signal for the next step in a given cascade. In a protein kinase cascade, the receptor is a kinase that then sends a signal to the next step of the cascade.Textbook Reference: 7.3 How Is a Response to a Signal Transduced through the Cell?Page: 137

5. Trace how changes in osmotic pressure in the plasma membrane of E. coli result in changes in gene transcription. What would be the outcome if OmpR could not bind to the ompC promoter?Answer: Refer to Figure 7.3 in the textbook. If OmpR could not bind to the ompC promoter, then the ompC gene would not be transcribed and translated, and the E. coli cell would be unable to prevent further solute entry into the inner membrane space.Textbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 130–132

TEXTBOOK SELF-QUIZ

1. What is the correct order for the following events in the interaction of a cell with a signal? (1) Alteration of cell function; (2) signal binds to receptor; (3) signal released from source; (4) signal transduction.a. 1234b. 2314c. 3214d. 3241e. 3421Answer: d

2. Why do some signals (“first messengers”) trigger “second messengers” to activate target cells?a. The first messenger requires activation by ATP.b. The first messenger is not water soluble.c. The first messenger binds to many types of cells.d. The first messenger cannot cross the plasma membrane.e. There are no receptors for the first messenger.Answer: d

3. Steroid hormones such as estrogen act on target cells bya. initiating second messenger activity.b. binding to membrane proteins.c. initiating gene expression.d. activating enzymes.e. binding to membrane lipids.Answer: c

4. The major difference between a cell that responds to a signal and one that does not is the presence of aa. DNA sequence that binds to the signal.b. nearby blood vessel.c. receptor.d. second messenger.e. transduction pathway.

Answer: c

5. Which of the following is not a consequence of a signal binding to a receptor?a. Activation of receptor enzyme activityb. Diffusion of the receptor in the plasma membranec. Change in conformation of the receptor proteind. Breakdown of the receptor to amino acidse. Release of the signal from the receptorAnswer: d

6. A nonpolar molecule such as a steroid hormone usually binds to aa. cytoplasmic receptor.b. protein kinase.c. ion channel.d. phospholipid.e. second messenger.Answer: a

7. Which of the following is not a common type of receptor?a. Ion channelb. Protein kinasec. G protein–linked receptord. Cytoplasmic receptore. Adenylyl cyclaseAnswer: e

8. Which of the following is not true of a protein kinase cascade?a. The signal is amplified.b. A second messenger is formed.c. Target proteins are phosphorylated.d. The cascade ends up at the mitochondrion.e. The cascade begins at the plasma membrane.Answer: d

9. Which of the following is not a second messenger?a. Calcium ionb. Inositol trisphosphatec. ATPd. Cyclic AMPe. DiacylglycerolAnswer: c

10. Plasmodesmata and gap junctionsa. allow small molecules and ions to pass rapidly between cells.b. are both membrane-lined channels.c. are channels about 1 mm in diameter.

d. are present only once per cell.e. are involved in cell recognition.Answer: a

BIOPORTAL DIAGNOSTIC QUIZ (Personalized Study Plan Quiz)(By Richard McCarty)

1. Hormones are chemical signals thata. affect adjacent cells.b. work in prokaryotes.c. are autocrine signals.d. travel through circulatory systems.e. are paracrine signals.Answer: dTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 130Bloom’s Category: 2. Understanding

2. Chemical signal transduction pathwaysa. use non-specific receptors.b. involve binding of the signal molecule to receptors.c. use receptors that are located only on the plasma membrane.d. always result in increased transcription of a gene.e. all use G proteins.Answer: bTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 130Bloom’s Category: 2. Understanding

3. EnvZ of E. colia. is present in the outer membrane of the bacterium.b. is a peripheral membrane protein.c. senses when the bacterium is in a region of high external solute concentration.d. directly affects solute entry into the cell.e. binds directly to DNA.Answer: cTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 131Bloom’s Category: 4. Analyzing

4. The active responder in the EnvZ signal transduction system is _______ and it _______ the protein _______.a. OmpR; increases the synthesis of; OmpCb. phosphorylated OmpR; increases the synthesis of; OmpCc. OmpR; phosphorylates; OmpC

d. phosphorylated OmpR; phosphorylates; OmpCe. OmpC: increases the synthesis of; OmpRAnswer: bTextbook Reference: 7.1 What Are Signals, and How Do Cells Respond to Them?Page: 131–132Bloom’s Category: 4. Analyzing

5. A universal feature of receptors is that theya. are present in the plasma membrane.b. are protein kinases.c. undergo structural (shape) changes when the signal molecule is bound.d. are ion channel proteins.e. are effector proteins.Answer: cTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 132–133Bloom’s Category: 4. Analyzing

6. Receptors resemble enzymes in thata. receptors and enzymes (most often) are polysaccharides.b. receptors and enzymes may be either integral membrane proteins or soluble proteins.c. receptor ligands, like enzyme substrates, are altered during signal transduction.d. receptors and enzymes are not specific for the molecules they bind.e. receptors generally have enzymatic activity.Answer: bTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 132–136Bloom’s Category: 2. Understanding

7. Which of the following signal molecules would most likely have a cytoplasmic receptor?a. A highly charged small moleculeb. A polypeptidec. A small nonpolar moleculed. A phospholipide. A polynucleotideAnswer: cTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 133Bloom’s Category: 4. Analyzing

8. Caffeinea. is structurally related to GDP.b. binds to a receptor in the brain.c. causes signal transduction by itself.d. is a signal.

e. a depressant.Answer: bTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 133Bloom’s Category: 2. Understanding

9. The acetylcholine receptor is an example of a(n) _______ receptor, the insulin receptor an example of a(n) _______ receptor, and the epinephrine receptor an example of a(n) _______ receptor.a. G protein-linked; protein kinase; ion channelb. ion channel; protein kinase; G protein-linkedc. ion channel; G protein-linked; protein kinased. protein kinase: ion channel; G protein-linkede. protein kinase; G protein-linked; ion channelAnswer: bTextbook Reference: 7.2 How Do Signal Receptors Initiate a Cellular Response?Page: 134–135Bloom’s Category: 2. Understanding

10. Rasa. is a G protein.b. is always active in normal cells.c. is a protein kinase.d. is a receptor.e. is active in the nucleus.Answer: aTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 136–137Bloom’s Category: 1. Remembering

11. An external stimulus causes a specific intracellular response. Which is the most likely order in which signal transducers would work?a. G protein; cAMP; protein kinaseb. protein kinase; cAMP; G proteinc. cAMP; protein kinase; G proteind. protein kinase; G protein; cAMPe. cAMP; G protein; protein kinaseAnswer: aTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 138–139Bloom’s Category: 4. Analyzing

12. Which of the following statements is true?a. Glycogen phosphorylase in liver cells is always active.b. cAMP is referred to as a “first messenger.”c. Epinephrine directly activates adenylyl cyclase.

d. cAMP is referred to as a “second messenger.”e. Adenylyl cyclase is a protein kinase.Answer: dTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 138–139Bloom’s Category: 4. Analyzing

13. Adenylyl cyclasea. is located such that cAMP is made outside of cells.b. makes cAMP from ATP with the liberation of phosphate (Pi).c. is inactivated by activated G- proteins.d. makes cAMP from ATP with the liberation of pyrophosphate (PPi).e. is directly activated by receptors.Answer: dTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 138–139Bloom’s Category: 2. Understanding.

14. The second messengers derived from a phospholipid membrane lipida. include inositol trisphospate (IP3) and diacylglycerol (DAG).b. activate protein kinases.c. open Ca2+ channels.d. are formed from phosphatidyl choline.e. are formed from a phospholipid in the endoplasmic reticulum.Answer: aTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 139Bloom’s Category: 1. Remembering

15. Nitric oxide (NO)a. can be a second messenger.b. is a participant in some signal transduction pathways.c. directly relaxes smooth muscle.d. directly activates a Ca2+ channel in the endoplasmic reticulum.e. stimulates cAMP synthesis.Answer: bTextbook Reference: 7.3 How Is the Response to a Signal Transduced through the Cell?Page: 140–141Bloom’s Category: 4. Analyzing

16. Which of the following is not involved in the signal transduction pathway for the detection of odorants?a. A G proteinb. Adenylyl cyclasec. A specific odorant molecule receptord. A gated ion channel in the endoplasmic reticulum

e. A cAMP-gated ion channelAnswer: dTextbook Reference: 7.4 How Do Cells Change in Response to Signals?Page: 142–143Bloom’s Category: 4. Analyzing

17. Which of the following cellular responses to signal transduction would include activation of transcription?a. rapid enzyme activation.b. rapid enzyme inhibition.c. opening of ion channels in the plasma membrane.d. increased expression of certain genes.e. changes in the calcium concentration in the cytosol.Answer: dTextbook Reference: 7.4 How Do Cells Change in Response to Signals?Page: 142–144Bloom’s Category: 1. Remembering

18. The phosphorylation of proteins by ATPa. is catalyzed by enzymes known as “protein kinases.”b. always stimulates the activity of an enzyme.c. is catalyzed by adenyl cyclase.d. always takes place in the cytoplasm.e. is catalyzed by G proteins.Answer: aTextbook Reference: 7.4 How Do Cells Change in Response to Signals?Page: 143Bloom’s Category: 2. Understanding

19. Gap junctionsa. allow large molecules and ions to pass rapidly between cells.b. permit metabolic cooperation among linked cells.c. are formed by the peripheral membrane protein connexin.d. are present in many copies per cell.e. contain membrane lined bridges.Answer: bTextbook Reference: 7.5 How Do Cells Communicate Directly?Page: 144–145Bloom’s Category: 1. Remembering

20. Plasmodesmataa. are, like gap junctions, made of connexin.b. present in animal cells.c. can allow the passage of particles as large as viruses from cell to cell.d. have a pore diameter of 6 nm.e. are made from an endomembrane.

Answer: cTextbook Reference: 7.5 How Do Cells Communicate Directly?Page: 145Bloom’s Category: 1. Remembering