Cell Communication

4/7/13 Cell Communication

session.masteringbiology.com/myct/assignmentPrintView?assignmentID=1937215 1/25

Cell Communication

Due: 1:00pm on Monday, April 8, 2013

Note: You will receive no credit for late submissions. To learn more, read your instructor's Grading Policy

Activity: Overview of Cell Signaling

Click here to complete this activity.

Then answer the questions.

Part A

Which of these is a receptor molecule?

ANSWER:

Correct

This is a receptor molecule.

Part B

A signal transduction pathway is initiated when a _____ binds to a receptor.

ANSWER:

Correct

The binding of a signal molecule to a receptor initiates a signal transduction pathway.

Part C

Biol 1002 - Spring 2013

Cell Communication Resources

D

A

B

C

E

signal molecule

G protein

calmodulin

cyclic AMP

tyrosine kinase

Signed in as Nora Trejos Help Close

http://session.masteringbiology.com/myct/assignmentPrintView?assignmentID=1937215#

http://session.masteringbiology.com/myct/assignmentPrintView?assignmentID=1937215

http://redirect.prod.mastering.pearsoncmg.com/redirect/helpLink?env=prod&productID=MasteringBiology&role=student&type=standalone&topicID=



Which of these is a signal molecule?

ANSWER:

Correct

This is a signal molecule.

Part D

A signal molecule is also known as a(n) _____.

ANSWER:

Correct

A ligand is a signal molecule.

Part E

Which of these is the second of the three stages of cell signaling?

ANSWER:

Correct

Transduction is the second of the three stages of cell signaling.

Activity: Reception

B

D

E

A

C

ligand

protein

key

initiator

receptor

gene activation

reception

binding of a neurotransmitter to a plasma membrane receptor

transduction

cell response





Part A

Which of these receptors is NOT a membrane receptor?

ANSWER:

Correct

This receptor is not associated with the plasma membrane.

Part B

Which of these is a G-protein-linked receptor?

ANSWER:

Correct

This is a G-protein-linked receptor.

Part C

Which of these is a receptor tyrosine kinase?

C

A

B

D

E

D

C

A

E

B





ANSWER:

Correct

This is a receptor tyrosine kinase.

Part D

Which of these is an ion-channel receptor?

ANSWER:

Correct

This receptor does form a channel.

Part E

The binding of signal molecules to _____ results in the phosphorylation of tyrosines.

ANSWER:

A

C

D

B

E

D

A

B

E

C



Correct

The binding of signal molecules to tyrosine-kinase receptors activates tyrosine-kinase enzymes, which phosphorylate tyrosines.

Part F

Which of these receptor molecules would allow Na+ to flow into the cell?

ANSWER:

Correct

This is an ion-channel receptor.

Part G

Which of these extracellular signal molecules could diffuse through a plasma membrane and bind to an intracellular receptor?

ANSWER:

Correct

Nonpolar molecules can diffuse through the plasma membrane and bind to intracellular receptors.

Part H

A(n) _____ is an example of a signal molecule that can bind to an intracellular receptor and thereby cause a gene to be turned on or off.

ANSWER:

D

B

C

E

A

B

D

E

A

C

starch

glycerol

estrogen

glucose

cellulose



Correct

Steroids bind to intracellular receptors, which can then bind to, and regulate, the expression of genes.

Part I

_____ is a signal molecule that binds to an intracellular receptor

ANSWER:

Correct

Steroids are nonpolar and can diffuse through the plasma membrane.

Part J

Thyroid hormones bind to _____ receptors.

ANSWER:

Correct

Thyroid hormones are able to pass through the plasma membrane.

Chapter 11 Pre-Test Question 5

Part A

What is the function of tyrosine-kinase receptors?

Hint 1.

steroid

ion

protein

carbohydrate

nucleic acid

C

B

D

A

E

intracellular

plasma membrane ion-channel

tyrosine-kinase

G-protein-linked

steroid



Remember the properties of a kinase.

ANSWER:

Correct

Phosphorylated tyrosine-kinase receptors then interact with relay proteins within the cell.


Part A

To what does the term "ligand" refer in cell biology?

Hint 1.

To ligate means to tie, or join.

ANSWER:

Correct

Ligands are the small signaling molecules that bind specifically to corresponding protein-receptor molecules.

Activity: Signal Transduction Pathways



Part A

Which of these acts as a second messenger?

enzymatic degrading of GTP to GDP

enzymatic hydrolyzing of the signaling molecule shortly after its arrival

enzymatic phosphorylation of tyrosine in the receptor protein

allowing specific ions to enter the cell after ligand binding

binding to nonpolar signaling molecules such as nitric oxide or the steroid hormones

any small molecule that can bind in a specific manner to a larger one

the change in shape that occurs when a signaling molecule binds to its receptor

the bond that forms between a signaling molecule and its receptor

the target cell of a signal molecule

a molecule that can occupy a receptor site while not activating the receptor





ANSWER:

Correct

This is a second messenger.

Part B

Which of these is responsible for initiating a signal transduction pathway?

ANSWER:

Correct

This is a signal molecule. The attachment of a signal molecule to a plasma membrane receptor initiates a signal transduction pathway.

Part C

What role does a transcription factor play in a signal transduction pathway?

ANSWER:

C

D

E

B

A

A

B

C

D

E

By binding to a plasma membrane receptor it initiates a cascade.

It relays a signal from the cytoplasm to the plasma membrane.

It activates relay proteins.

By binding to DNA it triggers the transcription of a specific gene.

It is a plasma membrane protein that binds signal molecules.



Correct

This is the function of a transcription factor.

Part D

In this animation, which of the following, when activated by a signal transduction pathway, moved from the cytoplasm to the nucleus of a cell?To view the animation, click here. Then click on the image to start the animation.

ANSWER:

Correct

Activated transcription factors trigger transcription.

Part E

Which of these is a membrane receptor?

ANSWER:

Correct

This is a receptor molecule.

Part F

A signal transduction pathway is initiated when a _____ binds to a receptor.

ANSWER:

relay protein

DNA

plasma membrane receptor protein

signal molecule

transcription factor

A

B

C

D

E

G protein

tyrosine kinase

calmodulin

signal molecule

cyclic AMP




Correct

The binding of a signal molecule to a receptor initiates a signal transduction pathway.

Part G

Which of these acts as a second messenger?

ANSWER:

Correct

Cyclic AMP can act as second messengers.

Part H

Calcium ions that act as second messengers are stored in _____.

ANSWER:

Correct

The ER stores calcium ions.

Part I

_____ catalyzes the production of _____, which then opens an ion channel that releases _____ into the cell's cytoplasm.

ANSWER:

Correct

Phospholipase C cleaves IP3 from a membrane protein, and IP3 then binds to a calcium channel on the ER.

Part J

A protein kinase activating many other protein kinases is an example of _____.

ANSWER:

G-protein-linked receptor

protein kinase

adenylyl kinase

cyclic AMP

G protein

lysosomes

endoplasmic reticula

chloroplasts

mitochondria

peroxisomes

Phospholipase C ... IP3 .... Ca2+

Adenylyl cyclase ... cyclic AMP ... Ca2+

Adenylyl cyclase ... IP3 .... Ca2+

Phospholipase C ... cyclic AMP ... Ca2+

Protein kinase ... PIP2 ... Na+



Correct

By activating many other molecules the initial signal is amplified.


Part A

Which of the following is a substance that acts at a long distance from the site at which it is secreted?

Hint 1.

Consider which of the following does not act locally.

ANSWER:

Correct

Both animals and plants use hormones for signaling at greater distances.

Cell Signaling: Reception

The process by which a signal is converted to a specific cellular response involves three stages:

1. reception of a signaling molecule2. transduction of the signal3. response to the signal

The diagram below shows a general cell signaling pathway. In this tutorial, you will demonstrate your understanding of signal reception. Keep in mind that asignal is only received by target cells that have receptors for that particular signaling molecule.

mutualism

amplification

a cellular response

sensitization

deactivation

paracrine signal

local regulator

neurotransmitter

synaptic signal

hormone



Part A - Intracellular receptors

Cortisol is a steroid hormone that can pass through the plasma membrane. Complete the flowchart describing the interaction of cortisol withintracellular receptors.

Drag the labels to their appropriate locations in the flowchart. Some labels will not be used.

Hint 1. Steroid hormones

Steroid hormones are chemical signaling molecules. Because they are usually small and hydrophobic, steroid hormones can readily passthrough a cell’s plasma membrane. The receptors for steroid hormones are usually located in the cytoplasm of target cells.

Hint 2. Definition of transcription factor

A transcription factor is a regulatory protein that binds to DNA and affects the transcription of specific genes.

Hint 3. What is the signaling mechanism of some steroid hormones?

The diagram below shows a steroid hormone interacting with an intracellular receptor.

Drag the labels to their appropriate locations next to the diagram.

ANSWER:



ANSWER:

Correct

Cortisol is a small, hydrophobic steroid hormone that can pass through the plasma membrane of cells. In target cells, cortisol binds to theintracellular receptor protein in the cytoplasm, forming a hormone-receptor complex. The hormone-receptor complex then moves into the nucleusand acts as a transcription factor, binding to specific genes and activating their transcription into mRNA. The mRNA that is produced is eventuallytranslated into specific proteins.Proteins produced in response to the cortisol signal function in the stress response. For example, some of these proteins aid in elevating glucoselevels in the blood, helping an animal to meet the demands of starvation or intense physical activity.

Part B - Comparing plasma membrane receptors

Unlike steroid hormones, signaling molecules that are large and/or hydrophilic cannot pass through the cell’s plasma membrane and therefore mustbind extracellularly to receptor molecules in the plasma membrane. Two types of signal receptors embedded in the cell's plasma membrane are Gprotein-coupled receptors and receptor tyrosine kinases. Classify each phrase by whether it applies to G protein-coupled receptors only, receptortyrosine kinases only, both receptors, or neither receptor.

Drag each phrase to the appropriate bin.

Hint 1. G protein-coupled receptors

A G protein-coupled receptor is a plasma membrane receptor composed of seven alpha helices that span the plasma membrane. As its namesuggests, a G protein-coupled receptor acts in conjunction with a G protein.The diagram below shows a G protein-coupled receptor in the absence of a signaling molecule. In the presence of a signaling molecule, the Gprotein-coupled receptor binds the G protein and activates it. The activated G protein then activates an associated enzyme, which can triggerthe next step in the signaling pathway.



Hint 2. How do G protein-coupled receptors function?

Which statements describe how G protein-coupled receptors function?

Select the three that apply.

ANSWER:

Hint 3. Receptor tyrosine kinases

Receptor tyrosine kinases are receptors that exhibit enzymatic activity. The diagram below depicts a common structure of receptor tyrosinekinases. In the absence of a signaling molecule, the receptors exist as individual proteins, as shown here. In the presence of a signalingmolecule, the proteins associate closely with each other (dimerize), prompting the transfer of phosphate groups from ATP to tyrosines. Otherrelay proteins bind to the phosphorylated tyrosines, become activated, and trigger transduction pathways that lead to cellular responses.

Hint 4. How do receptor tyrosine kinases function?

Which statements describe how receptor tyrosine kinases function?

Select the three that apply.

ANSWER:

Hint 5. Can you match terms related to receptors to their definitions?

Drag the terms on the left to the appropriate blanks on the right to complete the sentences.

ANSWER:

The binding of the signaling molecule opens or closes an ion channel.

The signaling molecule binds extracellularly to the G protein-coupled receptor.

When GDP is bound to a G protein, the G protein is inactive.

When GTP is bound to a G protein, the G protein is active.

The binding of the signaling molecules opens or closes an ion channel.

When signaling molecules bind, dimerization of monomer subunits occurs.

Receptor tyrosine kinases transfer phosphate groups from ATP to tyrosines.

The signaling molecules bind extracellularly to the receptor tyrosine kinases.



ANSWER:

Correct

Both G protein-coupled receptors and receptor tyrosine kinases are transmembrane receptors that have a binding domain located on theextracellular side of the plasma membrane. The binding of a signaling molecule to these receptors is the first step in a signaling pathway.However, what happens after a signaling molecule binds is different for each receptor.An activated G protein-coupled receptor activates a G protein inside the cell, which involves the release of GDP and the binding of GTP. Theactivated G protein then activates an associated enzyme, leading to a cellular response.Receptor tyrosine kinases form dimers after binding signaling molecules. The tyrosines are then phosphorylated, fully activating the receptor.Each phosphorylated tyrosine can bind a relay protein, each of which can trigger a transduction pathway. In this way, a single signaling-moleculebinding event can trigger multiple signal transduction pathways and thus multiple cellular responses.

Part C - Reception of the histamine signal

Histamine is a chemical substance released in inflammatory and allergic responses. The histamine H1 receptor on target cells is a G protein-coupledreceptor that activates phospholipase C in response to the binding of histamine.



Which statements are true about the binding of histamine to the histamine H1 receptor? Select all that apply.

Hint 1. Can you match terms related to cell signaling to their definitions?


ANSWER:

Hint 2. What is the likely mechanism of histamine signal reception?

Keep in mind that the H1 receptor is a G protein-coupled receptor that indirectly activates the enzyme phospholipase C.

Rank the steps from the first step through the last step.

ANSWER:

ANSWER:



Correct

When histamine encounters a target cell, it binds extracellularly to the H1 receptor, causing a change in the shape of the receptor. This change inshape allows the G protein to bind to the H1 receptor, causing a GTP molecule to displace a GDP molecule and activating the G protein. Theactive G protein dissociates from the H1 receptor and binds to the enzyme phospholipase C, activating it. The active phospholipase C triggers acellular response. The G protein then functions as a GTPase and hydrolyzes the GTP to GDP. The G protein dissociates from the enzyme and isinactive again and ready for reuse.

Cell Signaling: Transduction and Response

The process by which a signal is converted to a specific cellular response involves three stages:

1. reception of a signaling molecule2. transduction of the signal3. response to the signal

The diagram below shows a general cell signaling pathway. In this tutorial, you will demonstrate your understanding of signal transduction and cellularresponse to a signal. Keep in mind that a signal is only transduced into a cellular response by target cells with receptors for that particular signalingmolecule.

Histamine diffuses across the plasma membrane to bind to the H1 receptor.

Histamine binds extracellularly to the H1 receptor.

When histamine binds to the H1 receptor, the receptor undergoes a conformation change and binds the inactive G protein.

Histamine binds intracellularly to the inactive G protein, activating the G protein.

Once the G protein is active, it binds to the enzyme phospholipase C, activating it.

Histamine is likely hydrophilic.



Part A - Overview of cell signaling

Cell signaling involves converting extracellular signals to specific responses inside the target cell. Different molecules are involved at each stage of theprocess. In this activity, you will sort items based on which stage they are involved in: reception, transduction, or response.

Drag each item to the appropriate bin.

Hint 1. What do different terms associated with cell signaling mean?


ANSWER:

Hint 2. Which molecules are involved in the transduction stage of cell signaling?

Signal transduction pathways use many different molecules and ions in relaying a signal.

Which of the following molecules and ions participate in signal transduction pathways? Select the four that apply.

ANSWER:



ANSWER:

Correct

Receptor proteins (located in the plasma membrane or inside the cell) bind signaling molecules. The reception of the signal causes a shapechange in the receptor molecule, to which other molecules inside the cell respond. The message is then relayed through signal transduction,

which may involve a phosphorylation cascade or second messengers such as cAMP, Ca2+, or IP3. Possible responses to the signal may includesynthesis of a particular protein or regulation of a particular enzyme.

Part B - Transduction of the histamine signal

Histamine is a chemical substance released in inflammatory and allergic responses. The histamine H1 receptor is a G protein-coupled receptor thatactivates phospholipase C in response to the binding of histamine.

Complete the flowchart showing the process of histamine signal transduction from the H1 receptor.

Drag the labels to their appropriate locations in the flowchart. Some labels will not be used.

Hint 1. Formation of DAG and IP3

Both G protein-coupled receptors and receptor tyrosine kinases can initiate a pathway that uses the second messengers DAG and IP3. In thispathway, reception of the signaling molecule leads to the activation of the enzyme phospholipase C. Phospholipase C cleaves a membranephospholipid called PIP2 into DAG and IP3.

Hint 2. What are the descriptions of molecules involved in signal transduction pathways?

Drag the terms on the left to the appropriate blanks in the sentences on the right.

ANSWER:

Ca2+

cAMP

IP3

G protein-coupled receptor

adenylyl cyclase



Hint 3. What is the mechanism of the histamine signal transduction pathway?

The diagram below shows the general signal transduction pathway that is initiated by the binding of histamine at the H1 receptor. Read thediagram clockwise from the top left.

Drag the labels to their appropriate locations on the diagram below. Labels may be used once, more than once, or not at all.

ANSWER:

ANSWER:



Correct

After the reception of the histamine signaling molecule, the active G protein activates the enzyme phospholipase C. Phospholipase C cleavesPIP2 into DAG and IP3. IP3 diffuses through the cytosol and binds to an IP3-gated calcium channel in the ER membrane, causing it to open. As a

result, Ca2+ ions flow out of the ER and into the cytosol. The increase in the calcium ion concentration in the cytosol helps activate the cellularresponse.

Signal transduction pathways that involve phosphorylation cascades or multiple second messengers, such as histamine’s signal transductionpathway, enable a signal to be amplified and regulated at different points. Similarly, multistep pathways can facilitate the coordination of cellularresponses to multiple signals.

Part C - Cellular response to the histamine signal

The histamine H1 receptor is one of several existing histamine G protein-coupled receptors. Depending on many factors, including the type of receptor,histamine can trigger a variety of responses, including vasodilation, smooth muscle contraction, stimulation of gastric secretion, cardiac stimulation,and increased vascular permeability (causing runny nose and watery eyes).

Which of the following could account for the different cellular responses to histamine? Select all that apply.

Hint 1. Visualizing different responses to a signaling molecule

Consider how the cells in the diagrams below respond to the same signaling molecule. The purple and teal shapes represent different sets ofproteins.



Hint 2. What are the differences in the pathways?

In the following diagrams of four signaling pathways, how many different relay molecules respond to the same signaling molecule?

Count only the relay molecules that respond to the red signaling molecule. Enter your answer numerically.

ANSWER:

ANSWER:

Correct

When histamine binds to a histamine receptor, the specific cellular response that results is determined by the following factors:

the type of histamine receptorthe type of cell in which the receptor is locatedthe enzyme that is activated by the G protein associated with the receptorthe types of second messengers involved in the signal transduction pathwaythe proteins activated by the second messengers

Signaling molecules can trigger a multitude of cellular responses, which may ultimately affect the transcription of genes, the activity of proteins, orcell growth and division.

Activity: Build a Signaling Pathway


9

the cell type in which the histamine receptor is located

the type of signaling molecule

the types of relay molecules within the cell

the type of second messengers involved in the signal transduction pathway

the enzyme that is activated by the G protein associated with the receptor






Part A

Which of these is a logical signal transduction pathway?

ANSWER:

Correct

This is a logical sequence.

Activity: Cellular Responses



Part A

The cleavage of glycogen by glycogen phosphorylase releases _____.

ANSWER:

Correct

Glycogen is a polysaccharide composed of glucose monomers.

Part B

Epinephrine acts as a signal molecule that attaches to _____ proteins.

ANSWER:

An intracellular receptor activates phospholipase C, which cleaves a membrane protein to form IP3, which then activates the opening of anER channel protein, which releases cyclic AMP into the cytoplasm, where it binds to an intracellular enzyme that carries out a response.

An ion-channel receptor opens, allowing a steroid hormone to enter the cell; the steroid hormone then activates protein kinases that convertGTP to GDP, which binds to an intracellular enzyme that carries out a response.

A G-protein-linked receptor activates G protein, which activates phospholipase C, which cleaves a membrane lipid to form IP3, which binds toa calcium channel on the ER, which opens to release calcium ions into the cytoplasm, which bind to an intracellular enzyme that carries outa response.

A receptor tyrosine kinase activates adenylyl cyclase, which activates phospholipase C, which converts ATP into cyclic AMP, which bindsto an intracellular enzyme that carries out a response.

cellulose

nothing: glycogen phosphorylase cannot cleave glycogen

glucose-1-phosphate

fructose-1-phosphate

galactose-1-phosphate





Correct

Epinephrine acts via G-protein-linked receptors.

Part C

Which of these is a receptor for calcium ions?

ANSWER:

Correct

Calmodulin is a calcium ion receptor.

Part D

Which of these is NOT correct?

ANSWER:

Correct

Calcium binds to calmodulin.

Part E

A toxin that inhibits the production of GTP would interfere with the function of a signal transduction pathway that is initiated by the binding of a signalmolecule to _____ receptors.

ANSWER:

Correct

GTP activates G proteins.

G-protein-linked receptor

nuclear receptor

ion-channel receptor

intracellular receptor

receptor tyrosine kinase

IP3

adenylyl cyclase

PIP2

G protein

calmodulin

Tyrosine-kinase receptors consist of two polypeptides that join when activated by a signal molecule.

Cyclic AMP binds to calmodulin.

Kinases are enzymes that phosphorylate other molecules.

Phospholipase C catalyzes the formation of IP3.

Ion channels are found on both the plasma membrane and the endoplasmic reticulum.

ion-channel

G-protein-linked

receptor tyrosine kinase

intracellular

steroid



Misconception Question 51

Part A

What are the functions of signal transduction pathways?

Select all that apply.

ANSWER:

Correct

Signal transduction pathways perform all of these functions. Read about signal amplification and the specificity of cell signaling.

Misconception Question 53

Part A

Select the statement that correctly distinguishes between relay proteins and second messengers in signal transduction pathways.

ANSWER:

Correct

Read about signal transduction pathways, including relay proteins and second messengers.

Chapter 11 Question 41

Part A

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because

ANSWER:

Correct

Score Summary:

Your score on this assignment is 100%.You received 13.01 out of a possible total of 13 points.

Signal transduction pathways amplify the effect of a signal molecule.

Signal transduction pathways convert a signal on a cell’s surface to a specific cellular response.

Signal transduction pathways allow different types of cells to respond differently to the same signal molecule.

Relay proteins are the “first messengers,” the extracellular signaling molecules that bind to the membrane receptor. The signal transductionpathways are then formed by the second messengers, which are the relay molecules that respond to the first messengers.

Signal transduction pathways are multistep pathways in which relay proteins and second messengers alternate.

Signal transduction pathways are multistep pathways that include relay proteins and small, nonprotein, water-soluble molecules or ionscalled second messengers.

the number of molecules used is small and fixed.

they are species specific.

they counter the harmful effects of phosphatases.

they amplify the original signal manyfold.

they always lead to the same cellular response.

Documents

Cell Communication