chapter 11: Cell Communication (MasteringBiology- Pearson)

D

Which of these acts as a second messenger?

at the cytosol surface

A major group of G protein-coupled receptors contains seven transmembrane α helices. 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 face or on the cytosol face of the membrane. The loop on the cytosol side between helices 5 and 6 is usually substantially longer than the others. Where would you expect to find the carboxyl end?

amplification

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

ligand

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

signal molecule

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

G-protein-linked

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 signal molecule to _____ receptors.

steroid

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.

lysis of the cell

Apoptosis involves all but which of the following?

ligand-gated ion channel

Binding of a signaling molecule to which type of receptor leads directly to a change in the distribution of ions on opposite sides of the membrane?

cAMP

Caffeine is an inhibitor of phosphodiesterase. Therefore, the cells of a person who has recently consumed coffee would have increased levels of _____.

endoplasmic reticula

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

Reception: G protein-coupled receptor Receptor Tyrosine Kinase Signaling Molecule Transduction: Phosphorylation Cascade Second Messenger Adenylyl Cyclase IP3, Ca2+, cAMP Response: Protein Synthesis

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

during apoptosis, cellular agents chop up the DNA and fragment the organelles and other cytoplasmic components of a cell

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.

cAMP

Consider this pathway: epinephrine → G protein-coupled receptor → G protein → adenylyl cyclase → cAMP. Identify the second messenger.

1. Cortisol passes through the plasma membrane into the cytoplasm 2. Cortisol-receptor complex forms in the cytoplasm 3. Cortisol-receptor complex enters the nucleus where it binds to genes 4. Cortisol-receptor complex acts as a transcription factor 5. The transcribed mRNA is translated into a specific protein

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

Viagra inhibits the hydrolysis of cGMP to GMP

Cyclic GMP, or cGMP, acts as a signaling molecule whose effects include relaxation of smooth muscle cells in artery walls. In the penis, this signaling pathway and the resulting dilation of blood vessels leads to an erection. Select the correct statement about the effect of Viagra on this signaling pathway.

transcription factors

Dioxin, produced as a by-product of various industrial chemical processes, is suspected of contributing to the development of cancer and birth defects in animals and humans. It apparently acts by entering cells by simple diffusion and binding to proteins in the cytoplasm, then altering the pattern of gene expression. Which of the following are likely to be the cytoplasmic proteins to which dioxin binds?

G-protein-linked receptor

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

having multiple steps provides for greater possible amplification of a signal

For the greatest advantage of multiple steps in a transduction pathway is:

hydrolyzes GTP to GDP thus shutting down the pathway

GTPase activity is important in the regulation of signal transduction because it _____.

1) Enzyme cleaves PIP2, forming DAG and IP3 2)IP3 binds to a ligand-gated ion channel in the ER membrane 3) Calcium ions flow through the ligan-gated ion channel 4) Calcium ion concentration increases in the cytosol 5) Calcium ions activate a protein, leading to a cellular response

Histamine is a chemical substance released in inflammatory and allergic responses. The histamine H1 receptor is a G protein-coupled receptor that activates phospholipase C in response to the binding of histamine. Complete the flowchart showing the process of histamine signal transduction from 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 -Once the G protein is active, it binds to the enzyme phospholipase C, activating it -Histamine is likely hydrophilic

Histamine is a chemical substance released in inflammatory and allergic responses. The histamine H1 receptor on target cells is a G protein-coupled receptor 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?

signals would continue to be sent as there is no mechanism to turn off the signal

In a phosphorylation cascade (transduction pathway), a series of different molecules in a cell signaling pathway are phosphorylated. Each molecule adds a phosphate group to the next one in line. Protein phosphatases are enzymes that dephosphorylate each molecule returning the previous one to its inactive form. Use information from the figure to select which sentence best describes what would occur if the protein phosphatases were inhibited.

neurotransmitters

In the figure, the dots in the space between the two structures represent which of the following?

intracellular receptors are present only in target cells

Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells because _____.

If the patient's cancer cells have excessive levels of HER2

Particular receptor tyrosine kinases (RTKs) that promote excessive cell division are found at high levels on various cancer cells. A protein, Herceptin, has been found to bind to an RTK known as HER2. HER2 is sometimes excessive in cancer cells. This information can now be utilized in breast cancer treatment if which of the following is true?

they amplify the original signal manyfold

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

activation of G protein-coupled receptors

Protein phosphorylation is commonly involved with all of the following except _____.

signal transduction pathways are multistep pathways that include relay proteins and small, nonprotein, water-soluble molecules or ions called second messengers

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

dimerization and phosphorylation

The activation of receptor tyrosine kinases is characterized by _____.

C

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

the basic effect of the cholera toxin is signal amplification

The cholera bacterium Vibrio cholerae produces an enzyme toxin that chemically modifies a G protein involved in regulating salt and water secretion in intestinal cells. Stuck in its active form, the modified G protein stimulates the production of a high concentration of cAMP, which causes the intestinal cells to secrete large amounts of salts into the intestines, with water following by osmosis. An infected person quickly develops profuse diarrhea and if left untreated can soon die from the loss of water and salts. What is the basic effect of the cholera toxin?

glucose-1-phosphate

The cleavage of glycogen by glycogen phosphorylase releases _____.

inactivate protein kinases and turn off the signal transduction

The function of phosphatases in signal transduction is best described as to _____.

-the cell type in which the histamine receptor is located -the enzyme that is activated by the G protein associated with the receptor -the types of relay molecules within the cell -the type of second messengers involved in the signal transduction pathway

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?

intracellular

Thyroid hormones bind to _____ receptors.

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

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

G-protein: interact directly with G proteins Receptor tryosine kinases: catalyzes the transfer of a phosphate group t o the receptor, binding of the signaling molecule forms a dimer Both: binding site for signaling molecule is located on the extracellular side of cell, receptor is locate in plasma membrane Neither: binding of the signaling molecule allows ions to flow through a channel in the receptor

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

=Signal transduction pathways amplify the effect of a signal molecule =Signal transduction pathways allow different types of cells to respond differently to the same signal molecule =Signal transduction pathways convert a signal on a cell's surface to a specific cellular response

What are the functions of signal transduction pathways?

controlled cell suicide

What is apoptosis?

they might not be able to multiply in response to growth factors from nearby cells

What is most likely to happen to an animal's target cells that lack receptors for local regulators?

enzymatic phosphorylation of tyrosine in the receptor protein

What is the function of tyrosine-kinase receptors?

by binding to DNA it triggers the transcription of a specific gene

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

signal molecule

When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?

glycogen breakdown was observed only when epinephrine was administered to intact cells

Which observation suggested to Sutherland the involvement of a second messenger in epinephrine's effect on liver cells?

calcium ion and cAMP

Which of the following are among the most common second messengers?

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

Which of the following describes the events of apoptosis?

GTPase activity and hydrolysis of GTP to GDP

Which of the following is a correct association?

hormone

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

paracrine signaling

Which of the following is characterized by a cell releasing a signal molecule into the environment, followed by a number of cells in the immediate vicinity responding?

protein kinase activity

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

signal transduction molecules identified in distantly related organisms are similar

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

the molecular details of cell signaling are quite similar in organisms whose last common ancestor was a billion years ago

Which of the following provides molecular evidence that signal transduction pathways evolved early in the history of life?

-diffusion of a signaling molecule across the plasma membrane → binding of the signaling molecule to its receptor → movement of the signaling molecule-receptor complex into the nucleus → transcription -binding of a signaling molecule to its receptor → G protein activation → phospholipase C activation → IP3 production → increase in cytoplasmic calcium concentration -binding of a signaling molecule to its receptor → G protein activation → adenylyl cyclase activation → cAMP production → protein phosphorylation -binding of a growth factor to its receptor → phosphorylation cascade → activation of transcription factor → transcription

Which of the following sequences is correct? (All of these choices are correct)

synaptic

Which of the following types of signaling is represented in the figure?

cyclic AMP

Which of these acts as a second messenger?

estrogen

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

Cyclic AMP binds to calmodulin

Which of these is NOT correct?

A

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

B

Which of these is a membrane receptor?

B

Which of these is a receptor cell?

C

Which of these is a receptor tyrosine kinase?

A

Which of these is a signal molecule?

calmodulin

Which of these is activated by calcium ions?

D

Which of these is an ion-channel receptor?

A

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

transduction

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

D

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

E

Which of these receptors is NOT a membrane receptor?

protein kinases activate enzymes by phosphorylating or adding phosphate groups to them. Protein phosphatases dephosphorylate or remove phosphate groups from enzymes, including protein kinases

Which statement correctly distinguishes the roles of protein kinases and protein phosphatases in signal transduction pathways?

each step in a cascade produces a large number of activated products, causing signal amplification as the cascade progresses

Why are there often so many steps between the original signal event and the cell's response?

the transduction process is unique to each cell type; to respond to a signal, different cells require only a similar membrane receptor

Why can a signaling molecule cause different responses in different cells?

lysosomal enzymes exiting the dying cell would damage surrounding cells

Why is apoptosis potentially threatening to the healthy "neighbors" of a dying cell?

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

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

D

_____ is a signal molecule that binds to an intracellular receptor.