Question 1

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 2

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.

Question 3

Why does testosterone, a lipid-soluble signaling molecule that crosses the membranes of all cells, affect only target cells?

Accepted Answer

A)  Only target cells retain the appropriate genes regulated by testosterone. 
B)  Intracellular receptors for testosterone are present only in target cells. 
C)  Only target cells possess the cytosolic enzymes that transduce the signal from testosterone to adenylyl cyclase. 
D)  Only in target cells is testosterone able to initiate the phosphorylation cascade leading to activated transcription factor. 
A)  Only target cells retain the appropriate genes regulated by testosterone. 
B)  Intracellular receptors for testosterone are present only in target cells. 
C)  Only target cells possess the cytosolic enzymes that transduce the signal from testosterone to adenylyl cyclase. 
D)  Only in target cells is testosterone able to initiate the phosphorylation cascade leading to activated transcription factor.

Question 4

Which of the following activities would be inhibited by a drug that specifically blocks the addition of phosphate groups to proteins?

Accepted Answer

A)  binding of G proteins to G protein-coupled receptors 
B)  ligand-gated ion channel signaling pathways 
C)  adenylyl cyclase activity 
D)  receptor tyrosine kinase activity 
A)  binding of G proteins to G protein-coupled receptors 
B)  ligand-gated ion channel signaling pathways 
C)  adenylyl cyclase activity 
D)  receptor tyrosine kinase activity

Question 5

Protein kinase is an enzyme that functions in which of the following ways?

Accepted Answer

A)  as a second messenger molecule 
B)  as a receptor for various signal molecules 
C)  activates or inactivates other proteins by adding a phosphate group to them 
D)  activates a G protein 
A)  as a second messenger molecule 
B)  as a receptor for various signal molecules 
C)  activates or inactivates other proteins by adding a phosphate group to them 
D)  activates a G protein

Question 6

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

Accepted Answer

A)  Plant hormones frequently travel through the air as a gas. 
B)  Animal hormones are only local regulators. 
C)  Plant hormones commonly travel through the soil from one plant to another. 
D)  Animal hormones typically travel from the hormone producing cell to an adjacent responding cell through gap junctions. 
A)  Plant hormones frequently travel through the air as a gas. 
B)  Animal hormones are only local regulators. 
C)  Plant hormones commonly travel through the soil from one plant to another. 
D)  Animal hormones typically travel from the hormone producing cell to an adjacent responding cell through gap junctions.

Question 7

Lipid-soluble signaling molecules, such as aldosterone, cross the membranes of all cells but affect only target cells because

Accepted Answer

A)  only target cells retain the appropriate DNA segments. 
B)  intracellular receptors are present only in target cells. 
C)  only target cells have enzymes that break down aldosterone. 
D)  only in target cells is aldosterone able to initiate the phosphorylation cascade that turns genes on. 
A)  only target cells retain the appropriate DNA segments. 
B)  intracellular receptors are present only in target cells. 
C)  only target cells have enzymes that break down aldosterone. 
D)  only in target cells is aldosterone able to initiate the phosphorylation cascade that turns genes on.

Question 8

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 9

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 10

Which of the following amino acids are most frequently phosphorylated by protein kinases in the cytoplasm during signal transduction?

Accepted Answer

A)  tyrosines 
B)  glycine and histidine 
C)  serine and threonine 
D)  glycine and glutamic acid 
A)  tyrosines 
B)  glycine and histidine 
C)  serine and threonine 
D)  glycine and glutamic acid

Question 11

Which of the following statements is true of steroid receptors?

Accepted Answer

A)  The receptor molecules are themselves lipids or glycolipids. 
B)  The receptor may be inside the nucleus of a target cell. 
C)  The unbound steroid receptors are quickly recycled by lysosomes. 
D)  Steroid receptors are typically bound to the external surface of the nuclear membrane. 
A)  The receptor molecules are themselves lipids or glycolipids. 
B)  The receptor may be inside the nucleus of a target cell. 
C)  The unbound steroid receptors are quickly recycled by lysosomes. 
D)  Steroid receptors are typically bound to the external surface of the nuclear membrane.

Question 12

Many G protein-coupled receptors contain seven transmembrane α-helical domains. The amino end of the protein lies at the exterior of the plasma membrane. Loops of amino acids connect the helices either at the exterior surface or on the cytosolic surface of the membrane. The loop on the cytosolic side between helices 5 and 6 is usually substantially longer than the others. Where would you expect to find the carboxyl end of the protein?

Accepted Answer

A)  at the exterior surface 
B)  at the cytosolic surface 
C)  connected with the loop at H5 and H6 
D)  embedded in the phospholipid bilayer of the membrane 
A)  at the exterior surface 
B)  at the cytosolic surface 
C)  connected with the loop at H5 and H6 
D)  embedded in the phospholipid bilayer of the membrane

Question 13

One of the major categories of receptors in the plasma membrane functions by forming dimers, adding phosphate groups, and then activating relay proteins. Which type does this?

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 14

What is a primary function of transcription factors?

Accepted Answer

A)  They regulate the synthesis of DNA in response to a signal. 
B)  They convert ATP into cAMP. 
C)  They control gene expression. 
D)  They regulate the release of calcium from the endoplasmic reticulum. 
A)  They regulate the synthesis of DNA in response to a signal. 
B)  They convert ATP into cAMP. 
C)  They control gene expression. 
D)  They regulate the release of calcium from the endoplasmic reticulum.

Question 15

Protein phosphorylation is commonly involved with all of the following except

Accepted Answer

A)  activation of receptor tyrosine kinases. 
B)  activation of protein kinase molecules. 
C)  activation of G protein-coupled receptors. 
D)  regulation of transcription by signaling molecules. 
A)  activation of receptor tyrosine kinases. 
B)  activation of protein kinase molecules. 
C)  activation of G protein-coupled receptors. 
D)  regulation of transcription by signaling molecules.

Question 16

Which of the following is a type of local signaling in which a cell secretes a signal molecule that affects neighboring cells?

Accepted Answer

A)  hormonal signaling 
B)  autocrine signaling 
C)  paracrine signaling 
D)  synaptic signaling 
A)  hormonal signaling 
B)  autocrine signaling 
C)  paracrine signaling 
D)  synaptic signaling

Question 17

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 18

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 19

Which of the following provides the best evidence that cell-signaling pathways evolved early in the history of life?

Accepted Answer

A)  Cell-signaling pathways are seen in "primitive" cells such as bacteria and yeast. 
B)  Bacteria and yeast cells signal each other in a process called quorum sensing. 
C)  Signal transduction molecules identified in distantly related organisms are similar. 
D)  Most signals in all types of cells are received by cell surface receptors. 
A)  Cell-signaling pathways are seen in "primitive" cells such as bacteria and yeast. 
B)  Bacteria and yeast cells signal each other in a process called quorum sensing. 
C)  Signal transduction molecules identified in distantly related organisms are similar. 
D)  Most signals in all types of cells are received by cell surface receptors.

Question 20

Caffeine is an inhibitor of phosphodiesterase. Therefore, the cells of a person who has recently consumed coffee would have increased levels of which of the following molecules?

Accepted Answer

A)  phosphorylated proteins 
B)  cAMP 
C)  adenylyl cyclase 
D)  activated G proteins 
A)  phosphorylated proteins 
B)  cAMP 
C)  adenylyl cyclase 
D)  activated G proteins

Exam 11: Cell Communication

What are scaffolding proteins?

The activation of receptor tyrosine kinases is characterized by

Why does testosterone, a lipid-soluble signaling molecule that crosses the membranes of all cells, affect only target cells?

Which of the following activities would be inhibited by a drug that specifically blocks the addition of phosphate groups to proteins?

Protein kinase is an enzyme that functions in which of the following ways?

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

Lipid-soluble signaling molecules, such as aldosterone, cross the membranes of all cells but affect only target cells because

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

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

Which of the following amino acids are most frequently phosphorylated by protein kinases in the cytoplasm during signal transduction?

Which of the following statements is true of steroid receptors?

One of the major categories of receptors in the plasma membrane functions by forming dimers, adding phosphate groups, and then activating relay proteins. Which type does this?

What is a primary function of transcription factors?

Protein phosphorylation is commonly involved with all of the following except

Which of the following is a type of local signaling in which a cell secretes a signal molecule that affects neighboring cells?

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?

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

Which of the following provides the best evidence that cell-signaling pathways evolved early in the history of life?

Caffeine is an inhibitor of phosphodiesterase. Therefore, the cells of a person who has recently consumed coffee would have increased levels of which of the following molecules?

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

The Evolution of Populations

The Origin of Species

The History of Life on Earth

Phylogeny and the Tree of Life

Bacteria and Archaea

Protists

Plant Diversity I: How Plants Colonized Land

Plant Diversity II: The Evolution of Seed Plants

Fungi

An Overview of Animal Diversity

An Introduction to Invertebrates

The Origin and Evolution of Vertebrates

Vascular Plant Structure, Growth, and Development

Resource Acquisition and Transport in Vascular Plants

Soil and Plant Nutrition

Angiosperm Reproduction and Biotechnology

Plant Responses to Internal and External Signals

Basic Principles of Animal Form and Function

Animal Nutrition

Circulation and Gas Exchange

The Immune System

Osmoregulation and Excretion

Hormones and the Endocrine System

Animal Reproduction

Animal Development

Neurons, Synapses, and Signaling

Nervous Systems

Sensory and Motor Mechanisms

Animal Behavior

An Introduction to Ecology and the Biosphere

Population Ecology

Community Ecology

Ecosystems and Restoration Ecology

Conservation Biology and Global Change

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