Question 1

Which of the following statements about a G protein signalling 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 2

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 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)  increases glycogen phosphorylase activity in liver cells 
B)  activates adenylyl cyclase in liver cells 
C)  stimulates G protein activity in liver cells 
D)  increases phosphodiesterase activity in liver cells 
A)  increases glycogen phosphorylase activity in liver cells 
B)  activates adenylyl cyclase in liver cells 
C)  stimulates G protein activity in liver cells 
D)  increases phosphodiesterase activity in liver cells

Question 4

Apoptosis involves all but which of the following?

Accepted Answer

A)  fragmentation of the DNA 
B)  cell-signalling pathways 
C)  lysis of the cell 
D)  digestion of cellular contents by scavenger cells 
A)  fragmentation of the DNA 
B)  cell-signalling pathways 
C)  lysis of the cell 
D)  digestion of cellular contents by scavenger cells

Question 5

The activation of receptor tyrosine kinases is characterised by

Accepted Answer

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

Question 6

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

Accepted Answer

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

Question 7

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 8

What does it mean to say that a signal is transduced?

Accepted Answer

A)  The signal enters the cell directly and binds to a receptor inside. 
B)  The physical form of the signal changes as it passes from the cell membrane to the ultimate intracellular target. 
C)  The signal is amplified, such that even one signal molecule evokes a large response. 
D)  The signal triggers a sequence of phosphorylation events inside the cell. 
A)  The signal enters the cell directly and binds to a receptor inside. 
B)  The physical form of the signal changes as it passes from the cell membrane to the ultimate intracellular target. 
C)  The signal is amplified, such that even one signal molecule evokes a large response. 
D)  The signal triggers a sequence of phosphorylation events inside the cell.

Question 9

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 10

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 11

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 recognise 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 recognise and bind the hormone molecule.

Question 12

How does the toxin of Vibrio cholerae cause profuse diarrhoea?

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

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

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 15

In the formation of biofilms, such as those forming on unbrushed teeth, cell signalling 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 16

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 17

Lipid-soluble signalling 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 18

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 neighbouring 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 neighbouring 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

Question 19

Consider this pathway: adrenaline → 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 of the following statements describes the events of apoptosis?

Accepted Answer

A)  The cell dies, it is lysed, its organelles are phagocytised, and its contents are recycled. 
B)  The cell's DNA and organelles become fragmented, the cell dies, and it is phagocytised. 
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 specialised 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 phagocytised, and its contents are recycled. 
B)  The cell's DNA and organelles become fragmented, the cell dies, and it is phagocytised. 
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 specialised cells. 
D)  The cell's nucleus and organelles are lysed, and then the cell enlarges and bursts.

Exam 11: Cell Communication

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

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

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?

Apoptosis involves all but which of the following?

The activation of receptor tyrosine kinases is characterised by

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

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

What does it mean to say that a signal is transduced?

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?

How does the toxin of Vibrio cholerae cause profuse diarrhoea?

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?

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 signalling serves which function?

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?

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

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

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

Which of the following statements describes the events of apoptosis?

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 Colonised 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 Signalling

Nervous Systems

Sensory and Motor Mechanisms

Filters

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?