Question 1

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 2

An inhibitor of which of the following enzymes could be used to block the release of calcium from the endoplasmic reticulum?

Accepted Answer

A)  serine/threonine kinases 
B)  phosphodiesterase 
C)  phospholipase C 
D)  adenylyl cyclase 
A)  serine/threonine kinases 
B)  phosphodiesterase 
C)  phospholipase C 
D)  adenylyl cyclase

Question 3

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 4

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 5

Cells that are infected, damaged, or have reached the end of their functional life span often undergo "programmed cell death." This controlled cell suicide is called apoptosis. Select the appropriate description of this event on a cell's life cycle.

Accepted Answer

A)  Apoptosis is regulated by cell surface receptors that signal when a cell has reached its density-dependent limits. 
B)  During apoptosis, dying cells leak out their contents, including digestive enzymes that also destroy healthy cells. 
C)  During apoptosis, cellular agents chop up the DNA and fragment the organelles and other cytoplasmic components of a cell. 
D)  Each cell organelle has protein signals that initiate the breakdown of the organelle's components, which leads to cell death. 
A)  Apoptosis is regulated by cell surface receptors that signal when a cell has reached its density-dependent limits. 
B)  During apoptosis, dying cells leak out their contents, including digestive enzymes that also destroy healthy cells. 
C)  During apoptosis, cellular agents chop up the DNA and fragment the organelles and other cytoplasmic components of a cell. 
D)  Each cell organelle has protein signals that initiate the breakdown of the organelle's components, which leads to cell death.

Question 6

The receptors for steroid hormones are located inside the cell instead of the membrane surface like most other signal receptors. How do steroids gain access to their receptors?

Accepted Answer

A)  Steroid hormone receptors undergo conformational changes that relocate them on the membrane surface. 
B)  Both steroid hormones and their receptors are produced by the same cells. 
C)  Steroid hormones are lipid soluble, so they can readily diffuse through the lipid bilayer of the cell membrane. 
D)  Steroid hormones first bind to a steroid activator and this complex is transported across the cell membrane by a steroid transport protein. 
A)  Steroid hormone receptors undergo conformational changes that relocate them on the membrane surface. 
B)  Both steroid hormones and their receptors are produced by the same cells. 
C)  Steroid hormones are lipid soluble, so they can readily diffuse through the lipid bilayer of the cell membrane. 
D)  Steroid hormones first bind to a steroid activator and this complex is transported across the cell membrane by a steroid transport protein.

Question 7

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 8

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 9

Which of the following is a correct association?

Accepted Answer

A)  kinase activity and the addition of a tyrosine 
B)  phosphodiesterase activity and the removal of phosphate groups 
C)  GTPase activity and hydrolysis of GTP to GDP 
D)  adenylyl cyclase activity and the conversion of cAMP to AMP 
A)  kinase activity and the addition of a tyrosine 
B)  phosphodiesterase activity and the removal of phosphate groups 
C)  GTPase activity and hydrolysis of GTP to GDP 
D)  adenylyl cyclase activity and the conversion of cAMP to AMP

Question 10

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 11

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 12

Not all intercellular signals require transduction. Which one of the following signals would be processed without transduction?

Accepted Answer

A)  a lipid-soluble signal 
B)  a signal that is weakly bound to a nucleotide 
C)  a signal that binds to a receptor in the cell membrane 
D)  a signal that binds to the extracellular matrix 
A)  a lipid-soluble signal 
B)  a signal that is weakly bound to a nucleotide 
C)  a signal that binds to a receptor in the cell membrane 
D)  a signal that binds to the extracellular matrix

Question 13

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 14

Why has C. elegans proven to be a useful model for understanding apoptosis?

Accepted Answer

A)  C. elegans does not naturally use 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)  As C. elegans ages, its cells die progressively until the whole organism is dead. 
A)  C. elegans does not naturally use 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)  As C. elegans ages, its cells die progressively until the whole organism is dead.

Question 15

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

Question 16

Scientists have found that extracellular matrix components may induce specific gene expression in embryonic tissues such as the liver and testes. For this to happen, there must be direct communication between the extracellular matrix and the developing cells. Which kind of transmembrane protein would most likely be involved in this kind of induction?

Accepted Answer

A)  integrins 
B)  fibronectins 
C)  actin microfilaments 
D)  receptor tyrosine kinases 
A)  integrins 
B)  fibronectins 
C)  actin microfilaments 
D)  receptor tyrosine kinases

Question 17

Use the following figure to answer the question.
 
In the figure, the dots in the space between the two structures represent which of the following?

Accepted Answer

A)  receptor molecules 
B)  signal transducers 
C)  neurotransmitters 
D)  hormones 
A)  receptor molecules 
B)  signal transducers 
C)  neurotransmitters 
D)  hormones

Question 18

Which of the following results would most likely be an immediate result of a growth factor binding to its receptor?

Accepted Answer

A)  protein kinase activity 
B)  adenylyl cyclase activity 
C)  cAMP activity 
D)  phosphorylase activity 
A)  protein kinase activity 
B)  adenylyl cyclase activity 
C)  cAMP activity 
D)  phosphorylase activity

Question 19

Which of the following statements 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 20

If an adult person has a faulty version of the human analog to ced-4 of the nematode, which of the following is most likely to result?

Accepted Answer

A)  activation of a developmental pathway found in the worm but not in humans 
B)  a form of cancer in which there is insufficient apoptosis 
C)  formation of molecular pores in the mitochondrial outer membrane 
D)  excess skin loss 
A)  activation of a developmental pathway found in the worm but not in humans 
B)  a form of cancer in which there is insufficient apoptosis 
C)  formation of molecular pores in the mitochondrial outer membrane 
D)  excess skin loss

Exam 11: Cell Communication

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

An inhibitor of which of the following enzymes could be used to block the release of calcium from the endoplasmic reticulum?

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

The activation of receptor tyrosine kinases is characterized by

Cells that are infected, damaged, or have reached the end of their functional life span often undergo "programmed cell death." This controlled cell suicide is called apoptosis. Select the appropriate description of this event on a cell's life cycle.

The receptors for steroid hormones are located inside the cell instead of the membrane surface like most other signal receptors. How do steroids gain access to their receptors?

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

Which of the following is a correct association?

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

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?

Not all intercellular signals require transduction. Which one of the following signals would be processed without transduction?

Why has C. elegans proven to be a useful model for understanding apoptosis?

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?

Use the following figure to answer the question. In the figure, the dots in the space between the two structures represent which of the following?

Which of the following results would most likely be an immediate result of a growth factor binding to its receptor?

Which of the following statements describes the events of apoptosis?

If an adult person has a faulty version of the human analog to ced-4 of the nematode, which of the following is most likely to result?

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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