Question 1

Which statement about receptors is true?

Accepted Answer

A)  Receptors are found only on the surface of a cell. 
B)  A receptor is specific to a signal ligand. 
C)  Most receptors can bind many different signal ligands. 
D)  Most receptors have no connection to a signal transduction pathway. 
E)  Most receptors bind molecules that can diffuse through the cell membrane. 
A)  Receptors are found only on the surface of a cell. 
B)  A receptor is specific to a signal ligand. 
C)  Most receptors can bind many different signal ligands. 
D)  Most receptors have no connection to a signal transduction pathway. 
E)  Most receptors bind molecules that can diffuse through the cell membrane.

Question 2

Refer to the figure below.   Inositol trisphosphate (IP3) and calcium ions function as second messengers in the signal transduction pathway shown in the figure.Explain one similarity and one difference in the mechanisms of these two second messengers as components of this pathway.

Accepted Answer

Both are small and bind to sites on prot

Question 3

Gap junctions are channels that can allow the diffusion between cells of all of the following except

Accepted Answer

A)  small signal molecules. 
B)  ions. 
C)  certain hormones. 
D)  large proteins. 
E)  second messengers. 
A)  small signal molecules. 
B)  ions. 
C)  certain hormones. 
D)  large proteins. 
E)  second messengers.

Question 4

Which statement about ligands is false?

Accepted Answer

A)  An antagonist binds to a receptor protein in place of its ligand. 
B)  Drugs can function as ligands. 
C)  Ligands and receptors bind irreversibly, according to the law of mass action. 
D)  An inhibitor binds to a receptor protein in place of its ligand. 
E)  Antagonists acting as ligands can be natural or artificial. 
A)  An antagonist binds to a receptor protein in place of its ligand. 
B)  Drugs can function as ligands. 
C)  Ligands and receptors bind irreversibly, according to the law of mass action. 
D)  An inhibitor binds to a receptor protein in place of its ligand. 
E)  Antagonists acting as ligands can be natural or artificial.

Question 5

Caffeine is an example of a(n) _______ because it binds to a receptor that recognizes adenosine but does not elicit the same cellular response as adenosine.

Accepted Answer

A)  ligand 
B)  agonist 
C)  antagonist 
D)  signal molecule 
E)  hormone 
A)  ligand 
B)  agonist 
C)  antagonist 
D)  signal molecule 
E)  hormone

Question 6

Which example illustrates how an autocrine signal functions in the human body?

Accepted Answer

A)  Blood cells secrete a factor that binds to receptors on the same blood cells, causing them to proliferate. 
B)  To signal hunger, cells in the stomach secrete a peptide that circulates through the blood and binds to receptors on cells in the hypothalamus in the brain. 
C)  In the early stages of development, a cell produces a protein on its cell surface that comes into contact with a neighboring cell, where it binds to a receptor. 
D)  At the junction of two nerve cells, one of the cells secretes a neurotransmitter molecule that diffuses over to the neighboring cell, where it binds and stimulates an electrochemical response. 
E)  At a site of skin inflammation, chemical signals are sent from blood cells to the inflamed skin cells. 
A)  Blood cells secrete a factor that binds to receptors on the same blood cells, causing them to proliferate. 
B)  To signal hunger, cells in the stomach secrete a peptide that circulates through the blood and binds to receptors on cells in the hypothalamus in the brain. 
C)  In the early stages of development, a cell produces a protein on its cell surface that comes into contact with a neighboring cell, where it binds to a receptor. 
D)  At the junction of two nerve cells, one of the cells secretes a neurotransmitter molecule that diffuses over to the neighboring cell, where it binds and stimulates an electrochemical response. 
E)  At a site of skin inflammation, chemical signals are sent from blood cells to the inflamed skin cells.

Question 7

Gap junctions and plasmodesmata differ in that

Accepted Answer

A)  gap junctions are connected by protein tubules called connexons, whereas plasmodesmata are connected by extensions of the plant's cell walls. 
B)  gap junctions allow much larger molecules to pass through them. 
C)  gap junctions allow no real physical connection between cells; rather they are the spaces between cells. 
D)  one is found in animals and the other is found in plants. 
E)  gap junctions are connected by desmotubules, and plasmodesmata are connected by connexons. 
A)  gap junctions are connected by protein tubules called connexons, whereas plasmodesmata are connected by extensions of the plant's cell walls. 
B)  gap junctions allow much larger molecules to pass through them. 
C)  gap junctions allow no real physical connection between cells; rather they are the spaces between cells. 
D)  one is found in animals and the other is found in plants. 
E)  gap junctions are connected by desmotubules, and plasmodesmata are connected by connexons.

Question 8

The larger the dissociation constant KD is, the smaller will be

Accepted Answer

A)  the rate at which a ligand dissociates from its receptors. 
B)  the affinity of the receptor for its ligand. 
C)  the effect of a ligand on a signal transduction pathway. 
D)  the number of ligand molecules needed to stimulate a signal transduction pathway. 
E)  the number of cell surface receptors that bind a ligand. 
A)  the rate at which a ligand dissociates from its receptors. 
B)  the affinity of the receptor for its ligand. 
C)  the effect of a ligand on a signal transduction pathway. 
D)  the number of ligand molecules needed to stimulate a signal transduction pathway. 
E)  the number of cell surface receptors that bind a ligand.

Question 9

A mouse has a mutation in its oxytocin receptor that keeps the receptor in a constant state of activation.As a result, this mouse can be expected to be

Accepted Answer

A)  fearful. 
B)  trusting. 
C)  aggressive. 
D)  active. 
E)  curious. 
A)  fearful. 
B)  trusting. 
C)  aggressive. 
D)  active. 
E)  curious.

Question 10

Which statement about G protein-coupled receptors is false?

Accepted Answer

A)  Each receptor has seven transmembrane regions. 
B)  They are involved in light and odor detection. 
C)  They have an extracellular side and a cytoplasmic region. 
D)  Their ligands bind to the cytoplasmic region, which also binds to a G protein. 
E)  Ligand binding changes the shape of the G protein attached to the receptor. 
A)  Each receptor has seven transmembrane regions. 
B)  They are involved in light and odor detection. 
C)  They have an extracellular side and a cytoplasmic region. 
D)  Their ligands bind to the cytoplasmic region, which also binds to a G protein. 
E)  Ligand binding changes the shape of the G protein attached to the receptor.

Question 11

In designing a drug to function as an antagonist of a natural ligand in the human body, a pharmaceutical chemist would focus on mimicking which aspect of the natural ligand?

Accepted Answer

A)  Mass 
B)  Number of atoms 
C)  Orientation of functional groups 
D)  Number of chemical bonds 
E)  Density 
A)  Mass 
B)  Number of atoms 
C)  Orientation of functional groups 
D)  Number of chemical bonds 
E)  Density

Question 12

If a cell that normally produces juxtacrine signals is unable to produce signals during development, which cells will be most affected?

Accepted Answer

A)  Cells that are nearby but not in contact with the signaling cell's membrane 
B)  The signaling cell itself 
C)  Cells that serve as distant targets for the signals 
D)  Cells that normally receive signals through the circulatory system 
E)  Cells immediately adjacent to the signaling cell 
A)  Cells that are nearby but not in contact with the signaling cell's membrane 
B)  The signaling cell itself 
C)  Cells that serve as distant targets for the signals 
D)  Cells that normally receive signals through the circulatory system 
E)  Cells immediately adjacent to the signaling cell

Question 13

Sketch a signal transduction pathway.Include a protein kinase and/or a G protein-coupled receptor, at least one point at which the signal is amplified, and at least one second messenger.

Accepted Answer

There are many possible correct response

Question 14

Which experimental technique would be useful in determining whether a particular chemical signal is an autocrine or a paracrine signal?

Accepted Answer

A)  Observations of the behavior of single cells given no chemical treatment 
B)  Analysis of extracellular fluid surrounding cells 
C)  Gene expression analysis 
D)  Receptor compositional analysis 
E)  Observations of receptor specificity of signal binding 
A)  Observations of the behavior of single cells given no chemical treatment 
B)  Analysis of extracellular fluid surrounding cells 
C)  Gene expression analysis 
D)  Receptor compositional analysis 
E)  Observations of receptor specificity of signal binding

Question 15

Refer to the figure below.   The figure shows a protein receptor that functions in a signal transduction pathway.This receptor binds a ligand and then later binds an antagonist molecule.How do sections of the receptor shown in the figure change in response to the binding of each molecule?

Accepted Answer

A)  Section B, but not section C, undergoes a conformational change in response to the ligand and to the antagonist molecule. 
B)  Section C, but not section B, undergoes conformational change in response to the ligand and to the antagonist molecule. 
C)  Both sections C and B undergo conformational change in response to the ligand and to the antagonist molecule. 
D)  Both sections C and B undergo conformational change in response to the ligand but not to the antagonist molecule. 
E)  Both sections C and B undergo conformational change in response to the antagonist molecule but not to the ligand. 
A)  Section B, but not section C, undergoes a conformational change in response to the ligand and to the antagonist molecule. 
B)  Section C, but not section B, undergoes conformational change in response to the ligand and to the antagonist molecule. 
C)  Both sections C and B undergo conformational change in response to the ligand and to the antagonist molecule. 
D)  Both sections C and B undergo conformational change in response to the ligand but not to the antagonist molecule. 
E)  Both sections C and B undergo conformational change in response to the antagonist molecule but not to the ligand.

Question 16

IP3, nitric oxide, cAMP, and calcium ions are all examples of _______ that are used by signal transduction pathways.

Accepted Answer

Question 17

Refer to the figure and table below.     All four histamine receptors are G protein-coupled receptors that share many similarities in structure.However, each has a unique sequence and structure, and each has its own gene.With this information and the information in the table, predict an aspect that is likely shared by the four receptors and an aspect that differs.Explain your reasoning.

Accepted Answer

The four receptors likely share some str

Question 18

To respond to a signal, a cell must have a(n) _______ molecule that can detect the signal.

Accepted Answer

A)  paracrine 
B)  receptor 
C)  autocrine 
D)  response 
E)  recognition 
A)  paracrine 
B)  receptor 
C)  autocrine 
D)  response 
E)  recognition

Question 19

Which statement about ligand‒receptor complexes is false?

Accepted Answer

A)  For most ligand-receptor complexes, binding, as opposed to dissociation, is favored based on chemistry's law of mass action. 
B)  Ligand-receptor interactions are reversible. 
C)  Drugs that prevent binding of receptors' specific ligands can alter human behavior. 
D)  After binding to a cell membrane receptor, a ligand participates in the cellular response. 
E)  A ligand is a chemical signal. 
A)  For most ligand-receptor complexes, binding, as opposed to dissociation, is favored based on chemistry's law of mass action. 
B)  Ligand-receptor interactions are reversible. 
C)  Drugs that prevent binding of receptors' specific ligands can alter human behavior. 
D)  After binding to a cell membrane receptor, a ligand participates in the cellular response. 
E)  A ligand is a chemical signal.

Question 20

Which statement about signal transduction in cells can be used to explain how specificity is achieved in a signal transduction pathway?

Accepted Answer

A)  Receptors that bind chemical signals are either membrane receptors located on the cell surface or internal receptors present in the interior of a cell. 
B)  The sensitivity of a cell to a chemical signal is determined in part by the affinity of the cell's receptors for the signal molecule. 
C)  The binding of a small molecule to a site on a receptor is reversible, and equilibrium is reached when the rate of binding equals the rate of dissociation. 
D)  Agonists are chemicals that bind to a receptor and stimulate a signal transduction pathway just as the natural ligand does. 
E)  A receptor protein changes its conformation only when its binding site is occupied by a small molecule with a shape complementary to the site. 
A)  Receptors that bind chemical signals are either membrane receptors located on the cell surface or internal receptors present in the interior of a cell. 
B)  The sensitivity of a cell to a chemical signal is determined in part by the affinity of the cell's receptors for the signal molecule. 
C)  The binding of a small molecule to a site on a receptor is reversible, and equilibrium is reached when the rate of binding equals the rate of dissociation. 
D)  Agonists are chemicals that bind to a receptor and stimulate a signal transduction pathway just as the natural ligand does. 
E)  A receptor protein changes its conformation only when its binding site is occupied by a small molecule with a shape complementary to the site.

Exam 7: Cell Communication and Multicellularity

Which statement about receptors is true?

Refer to the figure below. Inositol trisphosphate (IP3) and calcium ions function as second messengers in the signal transduction pathway shown in the figure.Explain one similarity and one difference in the mechanisms of these two second messengers as components of this pathway.

Gap junctions are channels that can allow the diffusion between cells of all of the following except

Which statement about ligands is false?

Caffeine is an example of a(n) _______ because it binds to a receptor that recognizes adenosine but does not elicit the same cellular response as adenosine.

Which example illustrates how an autocrine signal functions in the human body?

Gap junctions and plasmodesmata differ in that

The larger the dissociation constant KD is, the smaller will be

A mouse has a mutation in its oxytocin receptor that keeps the receptor in a constant state of activation.As a result, this mouse can be expected to be

Which statement about G protein-coupled receptors is false?

In designing a drug to function as an antagonist of a natural ligand in the human body, a pharmaceutical chemist would focus on mimicking which aspect of the natural ligand?

If a cell that normally produces juxtacrine signals is unable to produce signals during development, which cells will be most affected?

Sketch a signal transduction pathway.Include a protein kinase and/or a G protein-coupled receptor, at least one point at which the signal is amplified, and at least one second messenger.

Which experimental technique would be useful in determining whether a particular chemical signal is an autocrine or a paracrine signal?

Refer to the figure below. The figure shows a protein receptor that functions in a signal transduction pathway.This receptor binds a ligand and then later binds an antagonist molecule.How do sections of the receptor shown in the figure change in response to the binding of each molecule?

IP3, nitric oxide, cAMP, and calcium ions are all examples of _______ that are used by signal transduction pathways.

To respond to a signal, a cell must have a(n) _______ molecule that can detect the signal.

Which statement about ligand‒receptor complexes is false?

Which statement about signal transduction in cells can be used to explain how specificity is achieved in a signal transduction pathway?

Studying Life

Small Molecules and the Chemistry of Life

Proteins, Carbohydrates, and Lipids

Nucleic Acids and the Origin of Life

Cells: the Working Units of Life

Cell Membranes

Energy, Enzymes, and Metabolism

Pathways That Harvest Chemical Energy

Photosynthesis: Energy From Sunlight

The Cell Cycle and Cell Division

Inheritance, Genes, and Chromosomes

Dna and Its Role in Heredity

From Dna to Protein: Gene Expression

Gene Mutation and Molecular Medicine

Regulation of Gene Expression

Genomes

Recombinant Dna and Biotechnology

Mechanisms of Evolution

Reconstructing and Using Phylogenies

Speciation

Evolution of Genes and Genomes

The History of Life on Earth

Bacteria, Archaea, and Viruses

The Origin and Diversification of Eukaryotes

Plants Without Seeds: From Water to Land

The Evolution of Seed Plants

The Evolution and Diversity of Fungi

Animal Origins and the Evolution of Body Plans

Protostome Animals

Deuterostome Animals

The Plant Body

Transport in Plants

Plant Nutrition

Regulation of Plant Growth

Reproduction in Flowering Plants

Plant Responses to Environmental Challenges

Physiology, Homeostasis, and Temperature Regulation

Animal Hormones

Immunology: Animal Defense Systems

Animal Reproduction

Animal Development

Neurons, Glia, and Nervous Systems

Sensory Systems

The Mammalian Nervous System: Structure and Higher Functions

Musculoskeletal Systems

Gas Exchange

Circulatory Systems

Nutrition, Digestion, and Absorption

Salt and Water Balance and Nitrogen Excretion

Animal Behavior

The Physical Environment and Biogeography of Life

Populations

Species Interactions

Communities

Ecosystems

A Changing Biosphere

Filters

Refer to the figure below. Inositol trisphosphate (IP₃) and calcium ions function as second messengers in the signal transduction pathway shown in the figure.Explain one similarity and one difference in the mechanisms of these two second messengers as components of this pathway.

The larger the dissociation constant K_Dis, the smaller will be

IP₃, nitric oxide, cAMP, and calcium ions are all examples of _______ that are used by signal transduction pathways.