Question 1

Which statement about intracellular receptors that respond to physical or chemical signals is false?

Accepted Answer

A)  Their ligands can be nonpolar molecules. 
B)  The estrogen receptor is intracellular. 
C)  Their chemical ligands are lipid-insoluble. 
D)  Light can excite intracellular receptors. 
E)  Intracellular receptors can be transcription factors. 
A)  Their ligands can be nonpolar molecules. 
B)  The estrogen receptor is intracellular. 
C)  Their chemical ligands are lipid-insoluble. 
D)  Light can excite intracellular receptors. 
E)  Intracellular receptors can be transcription factors.

Question 2

The membrane-lined tunnels that traverse the cell walls between plant cells are known as

Accepted Answer

A)  gap junctions. 
B)  plasmic junctions. 
C)  plasmodia. 
D)  plasmodesmata. 
E)  G protein-coupled receptors. 
A)  gap junctions. 
B)  plasmic junctions. 
C)  plasmodia. 
D)  plasmodesmata. 
E)  G protein-coupled receptors.

Question 3

Refer to the table below.   The table summarizes results of experiments using whole cells.Cells were either incubated without an enzyme (control) or incubated with an enzyme.Proteases degrade proteins, and glycosidases degrade oligosaccharides.Which hypothesis is supported by these results?

Accepted Answer

A)  Receptors for signal transduction pathways 1 and 2 bind the same ligands. 
B)  Receptors for signal transduction pathways 1 and 2 bind ligands that recognize glycoproteins. 
C)  Receptors for signal transduction pathways 1 and 2 bind ligands that recognize nonglycosylated proteins. 
D)  Pathway 1 involves a ligand that recognizes a nonglycosylated protein receptor, and pathway 2 involves a ligand that recognizes a glycoprotein receptor. 
E)  Pathway 1 involves a ligand that recognizes a glycoprotein receptor, and pathway 2 involves a ligand that recognizes a nonglycosylated protein receptor. 
A)  Receptors for signal transduction pathways 1 and 2 bind the same ligands. 
B)  Receptors for signal transduction pathways 1 and 2 bind ligands that recognize glycoproteins. 
C)  Receptors for signal transduction pathways 1 and 2 bind ligands that recognize nonglycosylated proteins. 
D)  Pathway 1 involves a ligand that recognizes a nonglycosylated protein receptor, and pathway 2 involves a ligand that recognizes a glycoprotein receptor. 
E)  Pathway 1 involves a ligand that recognizes a glycoprotein receptor, and pathway 2 involves a ligand that recognizes a nonglycosylated protein receptor.

Question 4

Some of the stem cells in bone become osteoclasts during differentiation.Researchers have shown that chemical signals called cytokines are released into the extracellular fluid by bone stem cells in response to environmental stimuli.The researchers also have shown that the cytokines induce these same bone stem cells to differentiate into osteoclasts.This example illustrates how a(n) _______ signal functions in the human body.

Accepted Answer

A)  autocrine 
B)  hormone 
C)  paracrine 
D)  juxtacrine 
E)  intracellular 
A)  autocrine 
B)  hormone 
C)  paracrine 
D)  juxtacrine 
E)  intracellular

Question 5

A molecule functioning as an antagonist binds to a(n)

Accepted Answer

A)  natural ligand. 
B)  artificial ligand, such as a drug. 
C)  adenosine molecule. 
D)  polar signal. 
E)  receptor protein. 
A)  natural ligand. 
B)  artificial ligand, such as a drug. 
C)  adenosine molecule. 
D)  polar signal. 
E)  receptor protein.

Question 6

Refer to the figure below.   A portion of a signal transduction pathway is shown in the figure.The molecule raf is a protein kinase.This molecule becomes activated when a GTP-ras complex binds to it.Which equation describes how activated raf transmits the signal in this pathway?

Accepted Answer

A)    ATP cAMP + PPi   
B)    cAMP AMP   
C)    Inactive enzyme + ATP active phosphorylated enzyme + ADP   
D)    Inactive phosphorylated enzyme + ADP inactive enzyme + ATP   
E)    Inactive enzyme + ADP active phosphorylated enzyme + ATP   
A)    ATP cAMP + PPi   
B)    cAMP AMP   
C)    Inactive enzyme + ATP active phosphorylated enzyme + ADP   
D)    Inactive phosphorylated enzyme + ADP inactive enzyme + ATP   
E)    Inactive enzyme + ADP active phosphorylated enzyme + ATP

Question 7

Refer to the table below.   The table summarizes characteristics of three compounds that relate to their function in two different signal transduction pathways.What can you infer about these three compounds from this information?

Accepted Answer

A)  The compounds X, Y, and Z have no structural features in common. 
B)  Compounds X and Y share some structural features but do not have much, if any, structural overlap with compound Z. 
C)  Compounds Y and Z share some structural features but do not have much, if any, structural overlap with compound X. 
D)  Compounds X and Z share some structural features but do not have much, if any, structural overlap with compound Y. 
E)  Compound Z shares some structural features with X and shares others with Y, but X and Y do not have much, if any, structural overlap with each other. 
A)  The compounds X, Y, and Z have no structural features in common. 
B)  Compounds X and Y share some structural features but do not have much, if any, structural overlap with compound Z. 
C)  Compounds Y and Z share some structural features but do not have much, if any, structural overlap with compound X. 
D)  Compounds X and Z share some structural features but do not have much, if any, structural overlap with compound Y. 
E)  Compound Z shares some structural features with X and shares others with Y, but X and Y do not have much, if any, structural overlap with each other.

Question 8

Which is a similarity between gap junctions and plasmodesmata?

Accepted Answer

A)  The connections between cells in both are lined by their fused plasma membranes. 
B)  Both structures are composed of connexons. 
C)  Both bring gases and nutrients to every cell through capillaries. 
D)  Both contain desmotubules derived from the endoplasmic reticulum. 
E)  The space available for diffusion within the channel is about the same. 
A)  The connections between cells in both are lined by their fused plasma membranes. 
B)  Both structures are composed of connexons. 
C)  Both bring gases and nutrients to every cell through capillaries. 
D)  Both contain desmotubules derived from the endoplasmic reticulum. 
E)  The space available for diffusion within the channel is about the same.

Question 9

A previously unknown chemical signal is discovered in mice.Five observations about this signal are listed.Which observation would serve as evidence in distinguishing whether this chemical signal should be classified as a juxtacrine or a paracrine signal?

Accepted Answer

A)  The signal molecule is a protein. 
B)  Cells responding to the signal have receptors specific to the signal. 
C)  Cells producing the signal are not affected by the signal molecule. 
D)  The signal molecule is not present in blood. 
E)  The signal molecule is not present in extracellular fluid. 
A)  The signal molecule is a protein. 
B)  Cells responding to the signal have receptors specific to the signal. 
C)  Cells producing the signal are not affected by the signal molecule. 
D)  The signal molecule is not present in blood. 
E)  The signal molecule is not present in extracellular fluid.

Question 10

Which are specialized cell junctions that allow neighboring cells to communicate directly with one another?

Accepted Answer

A)  Gated channels 
B)  Gap junctions 
C)  Cytoplasmic junctions 
D)  Ion channels 
E)  G proteins 
A)  Gated channels 
B)  Gap junctions 
C)  Cytoplasmic junctions 
D)  Ion channels 
E)  G proteins

Question 11

Refer to the figure below.   This figure is missing labels to show the types of enzymes catalyzing the forward and reverse reactions.The enzyme catalyzing the reaction producing the active form of the enzyme is a _______.

Accepted Answer

The answer of Refer to the figure below.  ...

Question 12

Second messengers

Accepted Answer

A)  are typically very specific in their activity. 
B)  are found in the cytoplasm. 
C)  are usually proteins. 
D)  do not amplify a signal. 
E)  are found in every signal transduction pathway. 
A)  are typically very specific in their activity. 
B)  are found in the cytoplasm. 
C)  are usually proteins. 
D)  do not amplify a signal. 
E)  are found in every signal transduction pathway.

Question 13

In order to respond to a signal, a cell must have a specific _______ that can detect the signal.

Accepted Answer

The answer of In order to respond to a signal,...

Question 14

Refer to the table below.   Listed are dissociation constants for five different ligands and their membrane receptors.The ligand with the highest affinity for its receptor is _______.

Accepted Answer

The answer of Refer to the table below.  ...

Question 15

Some tissues have only a few cells with the specific receptors needed for a signal response.How can the tissue respond most efficiently to that signal?

Accepted Answer

A)  Increase release of neurotransmitter. 
B)  Allow the signal to diffuse between cells via gap junctions. 
C)  Allow the circulatory system to carry the signal to other cells. 
D)  Increase gene expression for the receptor. 
E)  Increase the number of signaling molecules. 
A)  Increase release of neurotransmitter. 
B)  Allow the signal to diffuse between cells via gap junctions. 
C)  Allow the circulatory system to carry the signal to other cells. 
D)  Increase gene expression for the receptor. 
E)  Increase the number of signaling molecules.

Question 16

Refer to the figures below.   Chlamydomonas and Volvox are two algal genera in the phylum Chlorophyta.Which feature present in Volvox and absent in Chlamydomonas do scientists use as evidence to support their thinking about how multicellularity evolved?

Accepted Answer

A)  The ability to carry out photosynthesis 
B)  The ability to propel themselves through their environment 
C)  The ability of a cell to have more than one cellular phase 
D)  The ability of a cell to work cooperatively with other cells 
E)  The ability of a cell to change its function 
A)  The ability to carry out photosynthesis 
B)  The ability to propel themselves through their environment 
C)  The ability of a cell to have more than one cellular phase 
D)  The ability of a cell to work cooperatively with other cells 
E)  The ability of a cell to change its function

Question 17

The major difference between a cell that responds to a signal and one that does not is the presence of a

Accepted Answer

A)  DNA sequence that binds to the signal. 
B)  nearby blood vessel. 
C)  receptor. 
D)  second messenger. 
E)  transduction pathway. 
A)  DNA sequence that binds to the signal. 
B)  nearby blood vessel. 
C)  receptor. 
D)  second messenger. 
E)  transduction pathway.

Question 18

The membrane-lined tunnels called plamodesmata that connect adjacent plant cells

Accepted Answer

A)  have a large space for diffusion of cytoplasmic components between cells. 
B)  allow as much flow between cells as do gap junctions in animal cells. 
C)  contain channels made by connexons. 
D)  function primarily as tight junctions between cells. 
E)  have central tubes derived from the Golgi apparatus. 
A)  have a large space for diffusion of cytoplasmic components between cells. 
B)  allow as much flow between cells as do gap junctions in animal cells. 
C)  contain channels made by connexons. 
D)  function primarily as tight junctions between cells. 
E)  have central tubes derived from the Golgi apparatus.

Question 19

Plasmodesmata and gap junctions allow small molecules and ions to _______ rapidly between cells.

Accepted Answer

The answer of Plasmodesmata and gap junctions allow small molecules...

Question 20

A researcher working with mammalian kidney cells grown in culture observed that cells treated with a proteolytic enzyme (an enzyme that breaks down proteins) lost the ability to respond to the hormone vasopressin but not to the hormone aldosterone.Which is a reasonable explanation for this observation?

Accepted Answer

A)  The vasopressin receptor is a protein, whereas the aldosterone receptor is composed of either lipids or carbohydrates. 
B)  The cells lost the ability to synthesize the vasopressin receptor but retained the ability to synthesize the aldosterone receptor. 
C)  The vasopressin receptor is embedded in the cell membrane with an external portion that binds its ligand, whereas the aldosterone receptor is an intracellular receptor. 
D)  A debilitating mutation was introduced into the gene encoding the vasopressin receptor, but no such mutation affected the aldosterone receptor gene. 
E)  Vasopressin requires a receptor to stimulate a signal transduction pathway, whereas aldosterone can stimulate a signal transduction pathway without binding to a receptor. 
A)  The vasopressin receptor is a protein, whereas the aldosterone receptor is composed of either lipids or carbohydrates. 
B)  The cells lost the ability to synthesize the vasopressin receptor but retained the ability to synthesize the aldosterone receptor. 
C)  The vasopressin receptor is embedded in the cell membrane with an external portion that binds its ligand, whereas the aldosterone receptor is an intracellular receptor. 
D)  A debilitating mutation was introduced into the gene encoding the vasopressin receptor, but no such mutation affected the aldosterone receptor gene. 
E)  Vasopressin requires a receptor to stimulate a signal transduction pathway, whereas aldosterone can stimulate a signal transduction pathway without binding to a receptor.

Exam 7: Cell Communication and Multicellularity

Which statement about intracellular receptors that respond to physical or chemical signals is false?

The membrane-lined tunnels that traverse the cell walls between plant cells are known as

Refer to the table below. The table summarizes results of experiments using whole cells.Cells were either incubated without an enzyme (control) or incubated with an enzyme.Proteases degrade proteins, and glycosidases degrade oligosaccharides.Which hypothesis is supported by these results?

A molecule functioning as an antagonist binds to a(n)

Refer to the figure below. A portion of a signal transduction pathway is shown in the figure.The molecule raf is a protein kinase.This molecule becomes activated when a GTP-ras complex binds to it.Which equation describes how activated raf transmits the signal in this pathway?

Refer to the table below. The table summarizes characteristics of three compounds that relate to their function in two different signal transduction pathways.What can you infer about these three compounds from this information?

Which is a similarity between gap junctions and plasmodesmata?

A previously unknown chemical signal is discovered in mice.Five observations about this signal are listed.Which observation would serve as evidence in distinguishing whether this chemical signal should be classified as a juxtacrine or a paracrine signal?

Which are specialized cell junctions that allow neighboring cells to communicate directly with one another?

Refer to the figure below. This figure is missing labels to show the types of enzymes catalyzing the forward and reverse reactions.The enzyme catalyzing the reaction producing the active form of the enzyme is a _______.

Second messengers

In order to respond to a signal, a cell must have a specific _______ that can detect the signal.

Refer to the table below. Listed are dissociation constants for five different ligands and their membrane receptors.The ligand with the highest affinity for its receptor is _______.

Some tissues have only a few cells with the specific receptors needed for a signal response.How can the tissue respond most efficiently to that signal?

Refer to the figures below. Chlamydomonas and Volvox are two algal genera in the phylum Chlorophyta.Which feature present in Volvox and absent in Chlamydomonas do scientists use as evidence to support their thinking about how multicellularity evolved?

The major difference between a cell that responds to a signal and one that does not is the presence of a

The membrane-lined tunnels called plamodesmata that connect adjacent plant cells

Plasmodesmata and gap junctions allow small molecules and ions to _______ rapidly between cells.

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