Question 1

In yeast signal transduction, a yeast cell releases a mating factor, which ________.

Accepted Answer

A)  acts back on the same cell that secreted the mating factor, changing its development 
B)  passes through the membranes of neighboring cells, binds to DNA, and initiates transcription 
C)  binds to receptors on the membranes of other types of yeast cells 
D)  diffuses through the membranes of distant cells, causing them to produce factors that initiate long-distance migrations 
A)  acts back on the same cell that secreted the mating factor, changing its development 
B)  passes through the membranes of neighboring cells, binds to DNA, and initiates transcription 
C)  binds to receptors on the membranes of other types of yeast cells 
D)  diffuses through the membranes of distant cells, causing them to produce factors that initiate long-distance migrations C

Question 2

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

Accepted Answer

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

Question 3

If a pharmaceutical company wished to design a drug to maintain low blood sugar levels, one approach might be to design a compound that does which of the following?

Accepted Answer

A)  activates epinephrine receptors in liver cells 
B)  increases cAMP production in liver cells 
C)  blocks G protein activity in liver cells 
D)  increases glycogen phosphorylase activity in liver cells 
A)  activates epinephrine receptors in liver cells 
B)  increases cAMP production in liver cells 
C)  blocks G protein activity in liver cells 
D)  increases glycogen phosphorylase activity in liver cells C

Question 4

In research on aging (both cellular aging and organismal aging), it has been found that aged cells do not progress through the cell cycle as they had previously. Which of the following, if found in cells or organisms as they age, would provide evidence that this is related to cell signaling?

Accepted Answer

A)  Growth factor ligands do not bind as efficiently to receptors. 
B)  Hormone concentrations decrease. 
C)  cAMP levels change very frequently. 
D)  Enzymatic activity declines. 
A)  Growth factor ligands do not bind as efficiently to receptors. 
B)  Hormone concentrations decrease. 
C)  cAMP levels change very frequently. 
D)  Enzymatic activity declines.

Question 5

Which of the following is the most plausible explanation for why an animal cell would be unable to reduce the Ca²⁺ concentration in its cytosol compared with the extracellular fluid?

Accepted Answer

A)  inactivation of calcium-gated ion channels in the cell membrane 
B)  excessive transport of calcium from the cytosol into the endoplasmic reticulum 
C)  insufficient ATP levels in the cytosol 
D)  insufficient levels of protein kinase in the cell 
A)  inactivation of calcium-gated ion channels in the cell membrane 
B)  excessive transport of calcium from the cytosol into the endoplasmic reticulum 
C)  insufficient ATP levels in the cytosol 
D)  insufficient levels of protein kinase in the cell

Question 6

In the formation of biofilms, such as those forming on unbrushed teeth, cell signaling serves which function?

Accepted Answer

A)  formation of mating complexes 
B)  aggregation of bacteria that can cause cavities 
C)  secretion of substances that inhibit foreign bacteria 
D)  digestion of unwanted parasite populations 
A)  formation of mating complexes 
B)  aggregation of bacteria that can cause cavities 
C)  secretion of substances that inhibit foreign bacteria 
D)  digestion of unwanted parasite populations

Question 7

Use the following figure to answer the question.
 
Which of the following types of signaling is represented in the figure?

Accepted Answer

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

Question 8

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 9

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 10

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 11

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 12

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

Question 13

Viagra causes dilation of blood vessels and increased blood flow to the penis, facilitating erection. Viagra acts by inhibiting which of the following events?

Accepted Answer

A)  hydrolysis of cGMP to GMP 
B)  hydrolysis of GTP to GDP 
C)  dephosphorylation of cGMP 
D)  formation of cGMP from GTP 
A)  hydrolysis of cGMP to GMP 
B)  hydrolysis of GTP to GDP 
C)  dephosphorylation of cGMP 
D)  formation of cGMP from GTP

Question 14

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 15

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 16

Sutherland discovered that the signaling molecule epinephrine is responsible for which of the following events?

Accepted Answer

A)  Stimulating glycogen synthesis. 
B)  Decreasing blood glucose levels. 
C)  Interacting directly with glycogen phosphorylase. 
D)  Elevating cytosolic concentrations of cyclic AMP. 
A)  Stimulating glycogen synthesis. 
B)  Decreasing blood glucose levels. 
C)  Interacting directly with glycogen phosphorylase. 
D)  Elevating cytosolic concentrations of cyclic AMP.

Question 17

Particular receptor tyrosine kinases (RTKs) that promote excessive cell division are found at high levels in various cancer cells. HER2 is an RTK that is present at excessively high levels in some breast cancer cells. Herceptin is a protein that binds to HER2 and inhibits cell division. Herceptin may be an effective treatment for breast cancer treatment under which of the following conditions?

Accepted Answer

A)  If injection of HER2 in the patient's cancer cells stimulates cell division. 
B)  If the patient's cancer cells have excessive levels of HER2. 
C)  If the patient's genome codes for the HER2. 
D)  If the patient has excessive levels of other RTKs in cancer cells. 
A)  If injection of HER2 in the patient's cancer cells stimulates cell division. 
B)  If the patient's cancer cells have excessive levels of HER2. 
C)  If the patient's genome codes for the HER2. 
D)  If the patient has excessive levels of other RTKs in cancer cells.

Question 18

Consider this pathway:
Epinephrine → G protein-coupled receptor → G protein → adenylyl cyclase → cAMP
The second messenger in this pathway is ________.

Accepted Answer

A)  cAMP 
B)  G protein 
C)  adenylyl cyclase 
D)  G protein-coupled receptor 
A)  cAMP 
B)  G protein 
C)  adenylyl cyclase 
D)  G protein-coupled receptor

Question 19

What is the most likely mechanism by which testosterone functions inside a cell?

Accepted Answer

A)  It acts as a signal receptor that activates tyrosine kinases. 
B)  It binds with a receptor protein that enters the nucleus and activates expression of specific genes. 
C)  It acts as a steroid signal receptor that activates ion channel proteins in the plasma membrane. 
D)  It coordinates a phosphorylation cascade that reduces spermatogenesis. 
A)  It acts as a signal receptor that activates tyrosine kinases. 
B)  It binds with a receptor protein that enters the nucleus and activates expression of specific genes. 
C)  It acts as a steroid signal receptor that activates ion channel proteins in the plasma membrane. 
D)  It coordinates a phosphorylation cascade that reduces spermatogenesis.

Question 20

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 a coupled G protein most likely interact with this receptor?

Accepted Answer

A)  at the amino end 
B)  at the carboxyl end 
C)  along the exterior margin 
D)  at the loop between H5 and H6 
A)  at the amino end 
B)  at the carboxyl end 
C)  along the exterior margin 
D)  at the loop between H5 and H6

Exam 11: Cell Communication

In yeast signal transduction, a yeast cell releases a mating factor, which ________.

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

If a pharmaceutical company wished to design a drug to maintain low blood sugar levels, one approach might be to design a compound that does which of the following?

In research on aging (both cellular aging and organismal aging), it has been found that aged cells do not progress through the cell cycle as they had previously. Which of the following, if found in cells or organisms as they age, would provide evidence that this is related to cell signaling?

Which of the following is the most plausible explanation for why an animal cell would be unable to reduce the Ca²⁺ concentration in its cytosol compared with the extracellular fluid?

In the formation of biofilms, such as those forming on unbrushed teeth, cell signaling serves which function?

Use the following figure to answer the question. Which of the following types of signaling is represented in the figure?

Which of the following statements is true of steroid receptors?

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

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

What is a primary function of transcription factors?

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

Viagra causes dilation of blood vessels and increased blood flow to the penis, facilitating erection. Viagra acts by inhibiting which of the following events?

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

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

Sutherland discovered that the signaling molecule epinephrine is responsible for which of the following events?

Consider this pathway: Epinephrine → G protein-coupled receptor → G protein → adenylyl cyclase → cAMP The second messenger in this pathway is ________.

What is the most likely mechanism by which testosterone functions inside a cell?

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

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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

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DNA Tools and Biotechnology

Genomes and Their Evolution

Descent with Modification: A Darwinian View 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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Basic Principles of Animal Form and Function

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