Question 1

Which of the following processes generally requires protein phosphorylation?

Accepted Answer

A)  activation of receptor tyrosine kinases 
B)  activation of steroid hormone receptors 
C)  activation of G protein-coupled receptors 
D)  activation ligand-gated ion channels 
A)  activation of receptor tyrosine kinases 
B)  activation of steroid hormone receptors 
C)  activation of G protein-coupled receptors 
D)  activation ligand-gated ion channels

Question 2

Which of the following is true during a typical cAMP-mediated signal transduction event?

Accepted Answer

A)  The second messenger is the last part of the system to be activated. 
B)  A hormone activates the second messenger by directly binding to it. 
C)  The second messenger amplifies the hormonal response by attracting more hormones to the cell being affected. 
D)  Adenylyl cyclase is activated after the hormone binds to the cell and before phosphorylation of proteins occurs. 
A)  The second messenger is the last part of the system to be activated. 
B)  A hormone activates the second messenger by directly binding to it. 
C)  The second messenger amplifies the hormonal response by attracting more hormones to the cell being affected. 
D)  Adenylyl cyclase is activated after the hormone binds to the cell and before phosphorylation of proteins occurs.

Question 3

Which of the following statements about a G protein signaling pathway is true?

Accepted Answer

A)  A G protein-coupled receptor bound to GTP is in its active state. 
B)  A G protein bound to GTP is in its active state. 
C)  A G protein bound to GDP is in its active state. 
D)  Hydrolysis of bound GTP by a G protein activates the G protein. 
A)  A G protein-coupled receptor bound to GTP is in its active state. 
B)  A G protein bound to GTP is in its active state. 
C)  A G protein bound to GDP is in its active state. 
D)  Hydrolysis of bound GTP by a G protein activates the G protein.

Question 4

What are scaffolding proteins?

Accepted Answer

A)  microtubule arrays that allow lipid-soluble hormones to get from the cell membrane to the nuclear pores 
B)  large molecules to which several relay proteins attach to facilitate cascade effects 
C)  relay proteins that orient receptors and their ligands in appropriate directions to facilitate complex formation 
D)  proteins that enter the nucleus of a cell to regulate transcription 
A)  microtubule arrays that allow lipid-soluble hormones to get from the cell membrane to the nuclear pores 
B)  large molecules to which several relay proteins attach to facilitate cascade effects 
C)  relay proteins that orient receptors and their ligands in appropriate directions to facilitate complex formation 
D)  proteins that enter the nucleus of a cell to regulate transcription

Question 5

A mutation that knocks out the GTPase activity of a G protein would have what effect on a cell?

Accepted Answer

A)  The concentration of available GTP would decrease. 
B)  The number of G proteins in the cell would increase. 
C)  The G protein would be inactivated by a G protein-coupled receptor/signal molecule complex. 
D)  The G protein would always be active. 
A)  The concentration of available GTP would decrease. 
B)  The number of G proteins in the cell would increase. 
C)  The G protein would be inactivated by a G protein-coupled receptor/signal molecule complex. 
D)  The G protein would always be active.

Question 6

Hormones are chemical substances produced in one organ that are released into the bloodstream and affect the function of a target organ. Which of the following conditions is required for the target organ to respond to a particular hormone?

Accepted Answer

A)  Cells in the target organ must modify their plasma membranes to allow the hormone to enter the cytoplasm. 
B)  The target organ must be the same as the organ that produced the hormone. 
C)  The target organ must have the opposite mating type of the organ that produced the hormone. 
D)  The target organ must have receptors that recognize and bind the hormone molecule. 
A)  Cells in the target organ must modify their plasma membranes to allow the hormone to enter the cytoplasm. 
B)  The target organ must be the same as the organ that produced the hormone. 
C)  The target organ must have the opposite mating type of the organ that produced the hormone. 
D)  The target organ must have receptors that recognize and bind the hormone molecule.

Question 7

The activity of adenylyl cyclase is essentially the opposite of which of the following enzymes?

Accepted Answer

A)  protein kinase 
B)  protein phosphatase 
C)  phosphodiesterase 
D)  phosphorylase 
A)  protein kinase 
B)  protein phosphatase 
C)  phosphodiesterase 
D)  phosphorylase

Question 8

Yeast cells of mating type a are genetically engineered to produce only mating factor α instead of the normal mating factor a. The gene for the mating factor receptor was unaltered. How will these engineered cells behave in terms of mating?

Accepted Answer

A)  They will only mate with normal mating type a cells. 
B)  They will only mate with normal mating type α cells. 
C)  They will mate with each other or with normal mating type a cells, but not with normal mating type α cells. 
D)  They will only mate each other and not with normal mating type a or α cells. 
A)  They will only mate with normal mating type a cells. 
B)  They will only mate with normal mating type α cells. 
C)  They will mate with each other or with normal mating type a cells, but not with normal mating type α cells. 
D)  They will only mate each other and not with normal mating type a or α cells.

Question 9

In the nematode C. elegans, ced-9 prevents apoptosis in a normal cell in which of the following ways?

Accepted Answer

A)  It prevents the caspase activity of ced-3 and ced-4. 
B)  Ced-9 remains inactive until it is signaled by ced-3 and other caspases. 
C)  Ced-9 cleaves to produce ced-3 and ced-4. 
D)  Ced-9 prevents blebbing by its action on the cell membrane. 
A)  It prevents the caspase activity of ced-3 and ced-4. 
B)  Ced-9 remains inactive until it is signaled by ced-3 and other caspases. 
C)  Ced-9 cleaves to produce ced-3 and ced-4. 
D)  Ced-9 prevents blebbing by its action on the cell membrane.

Question 10

At puberty, an adolescent female body changes in both structure and function of several organ systems, primarily under the influence of changing concentrations of estrogen and other steroid hormones. How can one hormone, such as estrogen, mediate so many effects?

Accepted Answer

A)  Estrogen is produced in very large concentration by nearly every tissue of the body. 
B)  Each cell responds in the same way when steroids bind to the cell surface. 
C)  Estrogen is kept away from the surface of any cells, not able to bind it at the surface. 
D)  Estrogen binds to specific receptors inside many kinds of cells, each with different responses. 
A)  Estrogen is produced in very large concentration by nearly every tissue of the body. 
B)  Each cell responds in the same way when steroids bind to the cell surface. 
C)  Estrogen is kept away from the surface of any cells, not able to bind it at the surface. 
D)  Estrogen binds to specific receptors inside many kinds of cells, each with different responses.

Question 11

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because they ________.

Accepted Answer

A)  are species specific 
B)  always lead to the same cellular response 
C)  amplify the original signal many times 
D)  counter the harmful effects of phosphatases 
A)  are species specific 
B)  always lead to the same cellular response 
C)  amplify the original signal many times 
D)  counter the harmful effects of phosphatases

Question 12

Put the steps of the process of signal transduction in the order they occur.
1)A conformational change in the signal-receptor complex activates an enzyme.
2)Protein kinases are activated.
3)A signal molecule binds to a receptor.
4)Target proteins are phosphorylated.
5)Second messenger molecules are released.

Accepted Answer

A)  1, 2, 3, 4, 5 
B)  3, 1, 2, 4, 5 
C)  3, 1, 5, 2, 4 
D)  1, 2, 5, 3, 4 
A)  1, 2, 3, 4, 5 
B)  3, 1, 2, 4, 5 
C)  3, 1, 5, 2, 4 
D)  1, 2, 5, 3, 4

Question 13

A signal transmitted via phosphorylation of a series of proteins is generally associated with which of the following events?

Accepted Answer

A)  conformational changes to each protein in the series 
B)  binding of a hormone to an intracellular receptor 
C)  activation of a ligand-gated ion channel 
D)  production of ATP in the process of signal transduction 
A)  conformational changes to each protein in the series 
B)  binding of a hormone to an intracellular receptor 
C)  activation of a ligand-gated ion channel 
D)  production of ATP in the process of signal transduction

Question 14

If an animal cell suddenly lost the ability to produce GTP, what might happen to its signaling system?

Accepted Answer

A)  It would not be able to activate G proteins on the cytoplasmic side of the plasma membrane. 
B)  It would be able to carry out reception and transduction but would not be able to respond to a signal. 
C)  It would use ATP instead of GTP to activate G proteins on the cytoplasmic side of the plasma membrane. 
D)  It would not be able to activate receptor tyrosine kinases. 
A)  It would not be able to activate G proteins on the cytoplasmic side of the plasma membrane. 
B)  It would be able to carry out reception and transduction but would not be able to respond to a signal. 
C)  It would use ATP instead of GTP to activate G proteins on the cytoplasmic side of the plasma membrane. 
D)  It would not be able to activate receptor tyrosine kinases.

Question 15

Which of the following statements describes a likely effect of a drug designed that inhibits the cellular response to testosterone?

Accepted Answer

A)  The cytoplasmic levels of cAMP would decrease. 
B)  The transcription of certain genes would decrease. 
C)  The cytosolic calcium concentration would increase. 
D)  The activity of G proteins would decrease. 
A)  The cytoplasmic levels of cAMP would decrease. 
B)  The transcription of certain genes would decrease. 
C)  The cytosolic calcium concentration would increase. 
D)  The activity of G proteins would decrease.

Question 16

Binding of a signaling molecule to which type of receptor leads directly to a change in the distribution of ions on opposite sides of the membrane?

Accepted Answer

A)  receptor tyrosine kinase 
B)  G protein-coupled receptor 
C)  ligand-gated ion channel 
D)  steroid receptor 
A)  receptor tyrosine kinase 
B)  G protein-coupled receptor 
C)  ligand-gated ion channel 
D)  steroid receptor

Question 17

Which observation suggested to Sutherland the involvement of a second messenger in epinephrine's effect on liver cells?

Accepted Answer

A)  Enzymatic activity was proportional to the amount of calcium added to a cell-free extract. 
B)  Receptor studies indicated that epinephrine was a ligand. 
C)  Glycogen breakdown was observed only when epinephrine was administered to intact cells. 
D)  Glycogen breakdown was observed only when epinephrine and glycogen phosphorylase were mixed. 
A)  Enzymatic activity was proportional to the amount of calcium added to a cell-free extract. 
B)  Receptor studies indicated that epinephrine was a ligand. 
C)  Glycogen breakdown was observed only when epinephrine was administered to intact cells. 
D)  Glycogen breakdown was observed only when epinephrine and glycogen phosphorylase were mixed.

Question 18

How does the toxin of Vibrio cholerae cause profuse diarrhea?

Accepted Answer

A)  It modifies a G protein involved in regulating salt and water secretion. 
B)  It modifies adenylyl cyclase and triggers excess formation of cAMP. 
C)  It signals IP₃ to act as a second messenger for the release of calcium. 
D)  It modifies a ligand-gated ion channel. 
A)  It modifies a G protein involved in regulating salt and water secretion. 
B)  It modifies adenylyl cyclase and triggers excess formation of cAMP. 
C)  It signals IP₃ to act as a second messenger for the release of calcium. 
D)  It modifies a ligand-gated ion channel.

Question 19

Consider this pathway: epinephrine → G protein-coupled receptor → G protein → adenylyl cyclasec → AMP. Identify the second messenger.

Accepted Answer

A)  cAMP 
B)  G protein 
C)  GTP 
D)  adenylyl cyclase 
A)  cAMP 
B)  G protein 
C)  GTP 
D)  adenylyl cyclase

Question 20

Which observation suggested to Sutherland the involvement of a second messenger in epinephrine's effect on liver cells?

Accepted Answer

A)  Receptor studies indicated that epinephrine was a ligand. 
B)  Glycogen breakdown was observed only when epinephrine was administered to intact cells. 
C)  Glycogen breakdown was observed when epinephrine and glycogen phosphorylase were combined in a cell-free system. 
D)  Epinephrine was known to have different effects on many types of cells. 
A)  Receptor studies indicated that epinephrine was a ligand. 
B)  Glycogen breakdown was observed only when epinephrine was administered to intact cells. 
C)  Glycogen breakdown was observed when epinephrine and glycogen phosphorylase were combined in a cell-free system. 
D)  Epinephrine was known to have different effects on many types of cells.

Exam 11: Cell Communication

Which of the following processes generally requires protein phosphorylation?

Which of the following is true during a typical cAMP-mediated signal transduction event?

Which of the following statements about a G protein signaling pathway is true?

What are scaffolding proteins?

A mutation that knocks out the GTPase activity of a G protein would have what effect on a cell?

Hormones are chemical substances produced in one organ that are released into the bloodstream and affect the function of a target organ. Which of the following conditions is required for the target organ to respond to a particular hormone?

The activity of adenylyl cyclase is essentially the opposite of which of the following enzymes?

Yeast cells of mating type a are genetically engineered to produce only mating factor α instead of the normal mating factor a. The gene for the mating factor receptor was unaltered. How will these engineered cells behave in terms of mating?

In the nematode C. elegans, ced-9 prevents apoptosis in a normal cell in which of the following ways?

At puberty, an adolescent female body changes in both structure and function of several organ systems, primarily under the influence of changing concentrations of estrogen and other steroid hormones. How can one hormone, such as estrogen, mediate so many effects?

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because they ________.

A signal transmitted via phosphorylation of a series of proteins is generally associated with which of the following events?

If an animal cell suddenly lost the ability to produce GTP, what might happen to its signaling system?

Which of the following statements describes a likely effect of a drug designed that inhibits the cellular response to testosterone?

Binding of a signaling molecule to which type of receptor leads directly to a change in the distribution of ions on opposite sides of the membrane?

Which observation suggested to Sutherland the involvement of a second messenger in epinephrine's effect on liver cells?

How does the toxin of Vibrio cholerae cause profuse diarrhea?

Consider this pathway: epinephrine → G protein-coupled receptor → G protein → adenylyl cyclasec → AMP. Identify the second messenger.

Which observation suggested to Sutherland the involvement of a second messenger in epinephrine's effect on liver cells?

Evolution, the Themes of Biology, and Scientific Inquiry

The Chemical Context of Life

Water and Life

Carbon and the Molecular Diversity of Life

The Structure and Function of Large Biological Molecules

A Tour of the Cell

Membrane Structure and Function

An Introduction to Metabolism

Cellular Respiration and Fermentation

Photosynthesis

The Cell Cycle

Meiosis and Sexual Life Cycles

Mendel and the Gene Idea

The Chromosomal Basis of Inheritance

The Molecular Basis of Inheritance

Gene Expression: From Gene to Protein

Regulation of Gene Expression

Viruses

DNA Tools and Biotechnology

Genomes and Their Evolution

Descent with Modification: A Darwinian View of Life

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The Origin of Species

The History of Life on Earth

Phylogeny and the Tree of Life

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Plant Diversity I: How Plants Colonized Land

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An Overview of Animal Diversity

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Plant Responses to Internal and External Signals

Basic Principles of Animal Form and Function

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Osmoregulation and Excretion

Hormones and the Endocrine System

Animal Reproduction

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Neurons, Synapses, and Signaling

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