front 1 Which of the following are ways in which binding of a chemical messenger with a cell's receptor can bring about a cellular response? a. Opening or closing of specific ionic channels in the plasma membrane b. Activation of an intracellular second-messenger system c. Promoting or inhibiting the transcription of genes that code for the synthesis of cellular proteins d. Activating or inhibiting intracellular enzymes e. All of the choices are correct. | back 1 e. All of the choices are correct. |
front 2 The process whereby repeated exposure to a hormone can cause a decrease in the number of receptors for that hormone is called a. competition. b. inhibition. c. down-regulation. d. antagonism. e. saturation. | back 2 c. down-regulation. |
front 3 Epinephrine activates the cyclic AMP pathway in liver cells. In this example, epinephrine is a(n) __________ and cAMP is a(n) __________. a. ligand; receptor b. first messenger; hydrophobic hormone c. second messenger; ion channel d. first messenger; second messenger e. enzyme; second messenger | back 3 d. first messenger; second messenger |
front 4 With regard to the action of hormones and neurotransmitters on cellular receptors, which of these describes "amplification"? a. When the extracellular concentration of a chemical messenger reaches a very high level, it overwhelms transporter molecules and the chemical floods into the cell. b. Only hydrophilic first-messenger molecules can activate second-messenger molecules within the cell cytosol. c. A single first-messenger molecule activates multiple second-messenger molecules, each of which activate thousands of enzymes. d. Some cellular receptors have such low affinity for chemical ligands that it can require a million or more molecules to activate them. | back 4 c. A single first-messenger molecule activates multiple second-messenger molecules, each of which activate thousands of enzymes. |
front 5 Which is NOT typically a step in the cAMP second-messenger system? a. A first messenger binds to a transmembrane receptor. b. There is dissociation of G-protein subunits. c. An activated G-protein subunit phosphorylates cAMP-dependent protein kinase. d. Adenylyl cyclase converts ATP into cAMP. e. Active cAMP-dependent protein kinase phosphorylates cell proteins. | back 5 c. An activated G-protein subunit phosphorylates cAMP-dependent protein kinase. |
front 6 Second messengers a. are necessary for all receptor signal transduction mechanisms. b. act in the cell cytoplasm. c. only function as intercellular messengers. d. always function to activate enzymes. e. are always proteins. | back 6 b. act in the cell cytoplasm. |
front 7 Which of the following statements is TRUE? a. Phosphorylation by protein kinases can stimulate or inhibit the activity of effector proteins. b. Ca2+ is not a second messenger. c. Phosphodiesterase converts GMP into cGMP d. Conversion of ATP to cAMP is a phosphorylation reaction. e. Phospholipase C converts ATP to cAMP. | back 7 a. Phosphorylation by protein kinases can stimulate or inhibit the activity of effector proteins. |
front 8 Which of the following is known to be a second messenger? a. Diacylglycerol b. Phospholipase C c. ATP d. Adenylyl cyclase e. Epinephrine | back 8 a. Diacylglycerol |
front 9 Amplification during a second-messenger cascade is beneficial because amplification a. takes small molecules and makes polymers out of them. b. results in the production of more of the first messenger. d. allows a cell to respond to more different hormones. e. allows small amounts of hormones to produce large responses in target cells. | back 9 e. allows small amounts of hormones to produce large responses in target cells. |
front 10 What is a role of calcium ions in the second-messenger cascade involving phospholipase C, diacylglycerol, and inositol trisphosphate? a. It splits and activates G-protein subunits. b. It binds to the endoplasmic reticulum and causes the release of inositol trisphosphate. c. It phosphorylates cell proteins. d. It is the first messenger that binds to the integral membrane protein receptor. e. Along with diacylglycerol, it activates protein kinase C. | back 10 e. Along with diacylglycerol, it activates protein kinase C. |
front 11 What second messenger most directly causes calcium ions to be released from intracellular stores? a. Diacylglycerol b. Adenylyl cyclase c. inositol trisphosphate d. Phospholipase A e. Phospholipase C | back 11 c. inositol trisphosphate |
front 12 At very low concentrations, epinephrine causes an artery to dilate. At higher concentrations epinephrine causes the same artery to constrict. How can these different effects be explained? a. There is one type of epinephrine receptor that uses two second-messenger systems. b. There are two types of epinephrine receptors with different affinities for epinephrine that use two different second-messenger systems. c. There are two types of receptors for epinephrine that use the same second-messenger system. d. At higher concentrations epinephrine can pass through the plasma membrane and directly stimulate contraction within the cell. | back 12 b. There are two types of epinephrine receptors with different affinities for epinephrine that use two different second-messenger systems. |
front 13 One way that cells can increase their responsiveness to an external chemical regulator is by a. increasing the number of their transmembrane receptors by exocytosis. b. decreasing the number of their transmembrane receptors by endocytosis. c. uncoupling their receptors from the second message generator. d. increasing the number of their transmembrane receptors by endocytosis. e. mutating their extracellular receptors so that the affinity for the chemical regulator is reduced. | back 13 a. increasing the number of their transmembrane receptors by exocytosis. |
front 14 An adipose (fat) cell responds to the presence of the hormone epinephrine by increasing cytosolic cyclic AMP production, which leads to the catabolism of both glycogen and fat. What is the most likely explanation for this phenomenon? a. Epinephrine is binding to two types of receptors in the plasma membrane. b. The activated receptor complex stimulates production of two different second messengers. c. Cyclic AMP directly activates enzymes that catabolize glycogen and fat. d. Cyclic AMP-dependent protein kinase activates two kinds of enzymes. | back 14 d. Cyclic AMP-dependent protein kinase activates two kinds of enzymes. |
front 15 Designing a drug that blocked the release of eicosanoids would be an effective therapy for both pain and inflammation. True or False | back 15 True |
front 16 Type 2 diabetes mellitus is a disease in which the effect insulin has on the cell is reduced, despite consistent levels of circulating insulin (in the beginning of the disease). Which of the following could possibly explain this phenomenon? Check All That Apply a. Upregulation of insulin receptorsUpregulation of insulin receptors b. Downregulation of insulin receptors c. Increased affinity of insulin for its receptor d. Decreased expression of the second messenger in the insulin pathway e. Saturation of the insulin receptor | back 16 b. Downregulation of insulin receptors and d. Decreased expression of the second messenger in the insulin pathway |