Question 1

When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?

Accepted Answer

A)  relay molecule 
B)  transducer 
C)  signal molecule 
D)  response molecule 
A)  relay molecule 
B)  transducer 
C)  signal molecule 
D)  response molecule C

Question 2

Activation of which of the following molecules generally requires protein phosphorylation?

Accepted Answer

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

Question 3

In which of the following ways do plant hormones differ from hormones in animals?

Accepted Answer

A)  Plant hormones may travel through the air as a gas. 
B)  Plant hormones function as only paracrine signals. 
C)  Plant hormones may be transported from the hormone producing cell to the responding cell through a vascular system. 
D)  Plant hormones typically travel from the hormone producing cell to an adjacent responding cell through gap junctions. 
A)  Plant hormones may travel through the air as a gas. 
B)  Plant hormones function as only paracrine signals. 
C)  Plant hormones may be transported from the hormone producing cell to the responding cell through a vascular system. 
D)  Plant hormones typically travel from the hormone producing cell to an adjacent responding cell through gap junctions. A

Question 4

The dots in the space between the two structures in the accompanying figure represent which of the following components of a cell signaling pathway?

Accepted Answer

A)  receptor molecules 
B)  second messengers 
C)  neurotransmitters 
D)  hormones 
A)  receptor molecules 
B)  second messengers 
C)  neurotransmitters 
D)  hormones

Question 5

Which of the following observations suggests that a second messenger is required for the activation of glycogen phosphorylase by epinephrine?

Accepted Answer

A)  Glycogen phosphorylase is inactive in the absence of epinephrine in a cell-free system. 
B)  Glycogen breakdown occurs only when epinephrine is administered to intact cells. 
C)  Glycogen breakdown occurs when epinephrine and glycogen phosphorylase are combined in a cell-free system. 
D)  Epinephrine binds directly to glycogen phosphorylase. 
A)  Glycogen phosphorylase is inactive in the absence of epinephrine in a cell-free system. 
B)  Glycogen breakdown occurs only when epinephrine is administered to intact cells. 
C)  Glycogen breakdown occurs when epinephrine and glycogen phosphorylase are combined in a cell-free system. 
D)  Epinephrine binds directly to glycogen phosphorylase.

Question 6

Which of the following statements best describes steroid receptors?

Accepted Answer

A)  They are lipids or glycolipids. 
B)  They may be inside the nucleus of a target cell. 
C)  They are embedded in the plasma membrane. 
D)  They are typically bound to the external surface of the nuclear membrane. 
A)  They are lipids or glycolipids. 
B)  They may be inside the nucleus of a target cell. 
C)  They are embedded in the plasma membrane. 
D)  They are typically bound to the external surface of the nuclear membrane.

Question 7

Which of the following signal transduction proteins are activated by phosphorylation after binding to a signal molecule?

Accepted Answer

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

Question 8

If yeast cells of mating type α with normal mating factor receptors are genetically modified to produce only mating factor a, they will mate with which of the following cells?

Accepted Answer

A)  only normal mating type α cells 
B)  only normal mating type a cells 
C)  only normal mating type α cells, or with each other 
D)  only with each other 
A)  only normal mating type α cells 
B)  only normal mating type a cells 
C)  only normal mating type α cells, or with each other 
D)  only with each other

Question 9

Which of the following statements best describes a key aspect of a G protein signaling pathway?

Accepted Answer

A)  A G protein-coupled receptor is active when bound to GTP. 
B)  A G protein bound is active when bound to GTP. 
C)  A G protein bound is active when bound to GDP. 
D)  A G protein is activated by hydrolysis of bound GTP. 
A)  A G protein-coupled receptor is active when bound to GTP. 
B)  A G protein bound is active when bound to GTP. 
C)  A G protein bound is active when bound to GDP. 
D)  A G protein is activated by hydrolysis of bound GTP.

Question 10

Which of the following statements best describes the events of apoptosis?

Accepted Answer

A)  The cell dies, it is lysed, its organelles are phagocytized, and its contents are recycled. 
B)  The cell's DNA and organelles become fragmented, the cell dies, and it is phagocytized. 
C)  The cell's DNA and organelles become fragmented, the cell shrinks and forms blebs, and the cell's parts are packaged in vesicles that are digested by specialized cells. 
D)  The cell's nucleus and organelles are lysed, and then the cell enlarges and bursts. 
A)  The cell dies, it is lysed, its organelles are phagocytized, and its contents are recycled. 
B)  The cell's DNA and organelles become fragmented, the cell dies, and it is phagocytized. 
C)  The cell's DNA and organelles become fragmented, the cell shrinks and forms blebs, and the cell's parts are packaged in vesicles that are digested by specialized cells. 
D)  The cell's nucleus and organelles are lysed, and then the cell enlarges and bursts.

Question 11

Which of the following statements best describes a reason that C. elegans is an excellent model organism for investigating apoptosis?

Accepted Answer

A)  Cells in C. elegans do not naturally undergo apoptosis, but can be induced to do so in the laboratory. 
B)  C. elegans undergoes a fixed and easy-to-visualize number of apoptotic events during its normal development. 
C)  C. elegans has large cells wherein apoptosis is easily observed without the aid of a microscope. 
D)  Death in C. elegans through a well-defined sequence of apoptotic events. 
A)  Cells in C. elegans do not naturally undergo apoptosis, but can be induced to do so in the laboratory. 
B)  C. elegans undergoes a fixed and easy-to-visualize number of apoptotic events during its normal development. 
C)  C. elegans has large cells wherein apoptosis is easily observed without the aid of a microscope. 
D)  Death in C. elegans through a well-defined sequence of apoptotic events.

Question 12

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 13

Which of the following statements best would best explain the inability of an animal cell to reduce the Ca2+ concentration in its cytosol?

Accepted Answer

A)  The calcium-gated ion channels in the cell membrane are inactive. 
B)  Excessive amounts of calcium are transported from the cytosol into the endoplasmic reticulum. 
C)  Insufficient amounts of ATP are present in the cytosol. 
D)  Insufficient numbers of protein kinases are present in the cell. 
A)  The calcium-gated ion channels in the cell membrane are inactive. 
B)  Excessive amounts of calcium are transported from the cytosol into the endoplasmic reticulum. 
C)  Insufficient amounts of ATP are present in the cytosol. 
D)  Insufficient numbers of protein kinases are present in the cell.

Question 14

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 15

Which of the following statements best describes 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 16

Which of the following statements best describes 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 17

Which of the following enzymes essentially reverses the reaction catalyzed by adenylyl cyclase?

Accepted Answer

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

Question 18

Which of the following statements best describes an aspect of signal transduction?

Accepted Answer

A)  When signal molecules first bind to receptor tyrosine kinases, the receptors phosphorylate a number of nearby molecules. 
B)  In response to some G protein-mediated signals, a special type of lipid molecule associated with the plasma membrane is cleaved to form IP3 and calcium. 
C)  In most cases, signal molecules interact with the cell at the plasma membrane, enter the cell, and eventually enter the nucleus. 
D)  Protein kinase A activation is one possible result of signal molecules binding to G protein-coupled receptors. 
A)  When signal molecules first bind to receptor tyrosine kinases, the receptors phosphorylate a number of nearby molecules. 
B)  In response to some G protein-mediated signals, a special type of lipid molecule associated with the plasma membrane is cleaved to form IP3 and calcium. 
C)  In most cases, signal molecules interact with the cell at the plasma membrane, enter the cell, and eventually enter the nucleus. 
D)  Protein kinase A activation is one possible result of signal molecules binding to G protein-coupled receptors.

Question 19

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 20

The activation of receptor tyrosine kinases is characterized by ________.

Accepted Answer

A)  dimerization and phosphorylation 
B)  dimerization and IP3 binding 
C)  a phosphorylation cascade 
D)  GTP hydrolysis 
A)  dimerization and phosphorylation 
B)  dimerization and IP3 binding 
C)  a phosphorylation cascade 
D)  GTP hydrolysis

Exam 9: Cellular Signaling

When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?

Activation of which of the following molecules generally requires protein phosphorylation?

In which of the following ways do plant hormones differ from hormones in animals?

The dots in the space between the two structures in the accompanying figure represent which of the following components of a cell signaling pathway?

Which of the following observations suggests that a second messenger is required for the activation of glycogen phosphorylase by epinephrine?

Which of the following statements best describes steroid receptors?

Which of the following signal transduction proteins are activated by phosphorylation after binding to a signal molecule?

If yeast cells of mating type α with normal mating factor receptors are genetically modified to produce only mating factor a, they will mate with which of the following cells?

Which of the following statements best describes a key aspect of a G protein signaling pathway?

Which of the following statements best describes the events of apoptosis?

Which of the following statements best describes a reason that C. elegans is an excellent model organism for investigating apoptosis?

How does the toxin of Vibrio cholerae cause profuse diarrhea?

Which of the following statements best would best explain the inability of an animal cell to reduce the Ca2+ concentration in its cytosol?

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

Which of the following statements best describes scaffolding proteins?

Which of the following statements best describes a typical cAMP-mediated signal transduction event?

Which of the following enzymes essentially reverses the reaction catalyzed by adenylyl cyclase?

Which of the following statements best describes an aspect of signal transduction?

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

The activation of receptor tyrosine kinases is characterized by ________.

Biology and Its Themes

Atoms and Molecules

The Chemistry of Water

Carbon: the Basis of Molecular Diversity

Biological Macromolecules and Lipids

Energy and Life

Cell Structure and Function

Cell Membranes

Cell Respiration

Photosynthetic Processes

Mitosis

Sexual Life Cycles and Meiosis

Mendelian Genetics

Linkage and Chromosomes

Nucleic Acids and Inheritance

Expression of Genes

Control of Gene Expression

Dna Technology

The Evolution of Genomes

How Evolution Works

Phylogenetic Reconstruction

Microevolution

Species and Speciation

Macroevolution

Introduction to Viruses

Prokaryotes

The Origin and Evolution of Eukaryotes

Nonvascular and Seedless Vascular Plants

Seed Plants

Introduction to Fungi

An Introduction to Animal Diversity

Invertebrates

Vertebrates

Plant Structure and Growth

Transport in Vascular Plants

Plant Nutrition

Reproduction of Flowering Plants

Plant Signals and Behavior

The Animal Body

Chemical Signals in Animals

Animal Digestive Systems

Animal Transport Systems

Animal Excretory Systems

Animal Reproductive Systems

Development in Animals

Animal Defenses Against Infection

Electrical Signals in Animals

Neural Regulation in Animals

Sensation and Movement in Animals

An Overview of Ecology

Behavioral Ecology

Populations and Life History Traits

Biodiversity and Communities

Energy Flow and Chemical Cycling in Ecosystems

Conservation and Global Ecology

Filters