AP Biology CH 11

Which of the following is a substance that acts at a long distance from the site at which it is secreted? View Available Hint(s) local regulator synaptic signal neurotransmitter hormone paracrine signal

hormone

Thyroid hormones bind to _____ receptors.

intracellular

A G-protein receptor with GTP bound to it _____.

is in its active state

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

ligand

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?

ligand-gated ion channels

Which of these is activated by calcium ions? PIP2 IP3 adenylyl cyclase G protein calmodulin

calmodulin

Put the steps of the process of signal transduction in the order they occur: 1. A conformational change in the signal-receptor complex activates an enzyme. 2. Protein kinases are activated. 3. A signal molecule binds to a receptor. 4. Target proteins are phosphorylated. 5. Second messenger molecules are released.

3,1,5,2,4

What is apoptosis?

controlled cell suicide

Which of these extracellular signal molecules could diffuse through a plasma membrane and bind to an intracellular receptor? cellulose glycerol estrogen glucose starch

estrogen because its nonpolar

The cleavage of glycogen by glycogen phosphorylase releases _____.

glucose-1-phosphate

Classify each phrase by whether it applies to G protein-coupled receptors only, receptor tyrosine kinases only, both receptors, or neither receptor. binding of the signaling molecule allows ions to flow through a channel in the receptor interact directly with G proteins catalyzes the transfer of a phosphate group to the receptor binding site for signaling molecule is located on the extracellular side of the cell binding of the signaling molecule forms a dimer receptor is located in the plasma membrane

G protein-coupled receptors: interact directly with G proteins receptor tyrosine kinases: catalyzes the transfer of a phosphate group to the receptor, binding of the signaling molecule forms a dimer both: site for signaling molecule is located on the extracellular side of the cell, receptor is located in the plasma membrane neither: binding of the signaling molecule allows ions to flow through a channel in the receptor

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

G-protein-linked receptor

you know what to do.

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. (JUST REWRITE)

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.

g-protein-linked

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

The physical form of the signal changes from one form to another.

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. View Available Hint(s) a. the cell type in which the histamine receptor is located b. the types of relay molecules within the cell c. the type of signaling molecule d. the type of second messengers involved in the signal transduction pathway e. the enzyme that is activated by the G protein associated with the receptor

a, b, d, e

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

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

Which statement correctly distinguishes the roles of protein kinases and protein phosphatases in signal transduction pathways? a. Protein kinases activate enzymes by phosphorylating or adding phosphate groups to them. Protein phosphatases dephosphorylate or remove phosphate groups from enzymes, including protein kinases. b. Protein kinases are involved in signal transduction in unicellular eukaryotes such as yeast. Protein phosphatases are involved in signal transduction in multicellular eukaryotes. c. Protein kinases are more critical than protein phosphatases to signal transduction enzymes.

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

Select the statement that correctly distinguishes between relay proteins and second messengers in signal transduction pathways. a. Signal transduction pathways are multistep pathways that include relay proteins and small, nonprotein, water-soluble molecules or ions called second messengers. b. Relay proteins are the "first messengers," the extracellular signaling molecules that bind to the membrane receptor. The signal transduction pathways are then formed by the second messengers, which are the relay molecules that respond to the first messengers. c. Signal transduction pathways are multistep pathways in which relay proteins and second messengers alternate.

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

Which of the following provides molecular evidence that signal transduction pathways evolved early in the history of life? View Available Hint(s) a. The molecular details of cell signaling are quite similar in organisms whose last common ancestor was a billion years ago. b. Cell signaling is observed in organisms that do not utilize sexual reproduction. c. Simple forms of life, such as prokaryotic cells, utilize cell signaling. d. The pathways in primitive organisms, such as bacteria, are short, whereas those in advanced forms, such as mammals, are long. e. Receptor molecules have been identified in preparations of fossilized organisms billions of years old.

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

Which of the following is true of steroid receptors? a. The receptor may be inside the nucleus of a target cell. b. The unbound steroid receptors are quickly recycled by lysosomes. c. Steroid receptors are typically bound to the external surface of the nuclear membrane. d. The receptor molecules are themselves lipids or glycolipids.

a. The receptor may be inside the nucleus of a target cell.

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. a. Viagra inhibits the hydrolysis of cGMP to GMP. b. Viagra increases the rate of hydrolysis of cGMP to GMP. c. Viagra prevents the formation of cGMP.

a. Viagra inhibits the hydrolysis of cGMP to GMP.

Hormones are chemical substances produced in one organ that are released into the bloodstream and affect the function of a target organ. For the target organ to respond to a particular hormone, it must _____. a. have receptors that recognize and bind the hormone molecule b. be from the same cell type as the organ that produced the hormone c. experience an imbalance that disrupts its normal function d. modify its plasma membrane to alter the hormone entering the cytoplasm

a. have receptors that recognize and bind the hormone molecule

What are the functions of signal transduction pathways? Select all that apply. 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.

all

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

amplification

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

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

Which statements are true about the binding of histamine to the histamine H1 receptor? Select all that apply. View Available Hint(s) a. Histamine diffuses across the plasma membrane to bind to the H1 receptor. b. Histamine binds extracellularly to the H1 receptor. c. When histamine binds to the H1 receptor, the receptor undergoes a conformation change and binds the inactive G protein. d. Histamine binds intracellularly to the inactive G protein, activating the G protein. e. Once the G protein is active, it binds to the enzyme phospholipase C, activating it. f. Histamine is likely hydrophilic.

b, c, e, f

Why are there often so many steps between the original signal event and the cell's response? View Available Hint(s) a. Long, highly specific pathways minimize the possibility that a relay molecule accidentally could activate a pathway leading to a secondary response. b. Each step in a cascade produces a large number of activated products, causing signal amplification as the cascade progresses. c. The accumulation of genetic mutations over time has added redundant steps to the pathway. d. Lengthy pathways provide the opportunity for the initial pathway molecules to recycle back to inactive forms should additional signaling molecules be present. e. Each transduction is a checkpoint.

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

Which of the following poses the best evidence that cell-signaling pathways evolved early in the history of life? a. Most signals in all types of cells are received by cell surface receptors. b. Signal transduction molecules identified in distantly related organisms are similar. c. Bacteria and yeast cells signal each other in a process called quorum sensing. d. Cell-signaling pathways are seen in "primitive" cells such as bacteria and yeast.

b. Signal transduction molecules identified in distantly related organisms are similar.

Which of the following describes the events of apoptosis? a. The cell's nucleus and organelles are lysed, then the cell enlarges and bursts. b. 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. c. The cell dies, it is lysed, its organelles are phagocytized, and its contents are recycled. d. The cell's DNA and organelles become fragmented, the cell dies, and it is phagocytized.

b. 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.

Protein kinase is an enzyme that _____. a. serves as a receptor for various signal molecules b. activates or inactivates other proteins by adding a phosphate group to them c. functions as a second messenger molecule d. produces second messenger molecules

b. activates or inactivates other proteins by adding a phosphate group to them

Transcription factors _____. a. regulate the synthesis of lipids in the cytoplasm b. control gene expression c. regulate the synthesis of DNA in response to a signal d. transcribe ATP into cAMP

b. control gene expression

Which of the following is characteristic of a steroid hormone action? a. protein phosphorylation b. internal receptor binding c. second messenger activation d. cell-surface receptor binding

b. internal receptor binding

Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells because _____. a. only in target cells is testosterone able to initiate the phosphorylation cascade leading to activated transcription factor b. intracellular receptors are present only in target cells c. only target cells possess the cytosolic enzymes that transduce the testosterone d. only target cells retain the appropriate DNA segments

b. intracellular receptors are present only in target cells

Apoptosis involves all but which of the following? a. fragmentation of the DNA b. lysis of the cell c. digestion of cellular contents by scavenger cells d. activation of cellular enzymes

b. lysis of the cell

In general, a signal transmitted via phosphorylation of a series of proteins _____. a. generates ATP in the process of signal transduction b. results in a conformational change to each protein c. activates a transcription event d. requires binding of a hormone to an intracellular receptor

b. results in a conformational change to each protein

The receptors for steroid hormones are located inside the cell instead of on the membrane surface like most other signal receptors. This is not a problem for steroids because _____. a. the receptors can be readily stimulated to exit and relocate on the membrane surface b. steroid hormones are lipid soluble, so they can readily diffuse through the lipid bilayer of the cell membrane c. steroids do not directly affect cells but instead alter the chemistry of blood plasma d. steroids must first bond to a steroid activator, forming a complex that then binds to the cell surface

b. steroid hormones are lipid soluble, so they can readily diffuse through the lipid bilayer of the cell membrane

At puberty, an adolescent female body changes in both structure and function of several organ systems, primarily under the influence of changing concentrations of estrogens and other steroid hormones. How can one hormone, such as estrogen, mediate so many effects? a. Each cell responds in the same way when steroids bind to the cell surface. b. Estrogen is produced in very large concentration by nearly every tissue of the body. c. Estrogen binds to specific receptors inside many kinds of cells, each with different responses. d. Estrogen is kept away from the surface of any cells not able to bind it at the surface.

c. Estrogen binds to specific receptors inside many kinds of cells, each with different responses.

Which of the following is a correct association? a. adenylyl cyclase activity and the conversion of cAMP to AMP b. phosphodiesterase activity and the removal of phosphate groups c. GTPase activity and hydrolysis of GTP to GDP d. kinase activity and the addition of a tyrosine

c. GTPase activity and hydrolysis of GTP to GDP

Which of the following statements would explain what would occur as a result of the signal pathway represented by the diagram? a. DNA levels would increase in the nucleus as a result of the binding of the hormone-receptor complex with the DNA. b. Transfer RNA (t-RNA) would accumulate in high levels because it is not required for protein synthesis. c. Messenger RNA (m-RNA) levels would increase in order to be translated into the protein required by the cell. d. Ribosomal RNA (r-RNA) levels would increase because ribosomes are specific for the messenger RNA (m-RNA) with which they bind during transcription of the polypeptide.

c. Messenger RNA (m-RNA) levels would increase in order to be translated into the protein required by the cell.

In which of the following ways do plant hormones differ from hormones in animals? a. Animal hormones are primarily for mating and embryonic development. b. Animal hormones are only local regulators. c. Plant hormones most often travel in air as a gas. d. Plant hormones are typically released into the soil.

c. Plant hormones most often travel in air as a gas.

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? a. The basic effect of the cholera toxin is premature termination of a signaling pathway. b. The basic effect of the cholera toxin is loss of specificity of the response of intestinal cells to a signaling molecule. c. The basic effect of the cholera toxin is signal amplification.

c. The basic effect of the cholera toxin is signal amplification.

Protein phosphorylation is commonly involved with all of the following EXCEPT _____. a. activation of protein kinase molecules b. regulation of transcription by extracellular signaling molecules c. activation of G protein-coupled receptors d. enzyme activation

c. activation of G protein-coupled receptors

Testosterone functions inside a cell by _____. a. coordinating a phosphorylation cascade that increases spermatogenesis b. acting as a steroid signal receptor that activates ion channel proteins c. binding with a receptor protein that enters the nucleus and activates specific genes d. acting as a signal receptor that activates tyrosine kinases

c. binding with a receptor protein that enters the nucleus and activates specific genes

Sutherland discovered that the signaling molecule epinephrine _____. a. interacts directly with glycogen phosphorylase b. brings about a decrease in levels of cAMP as a result of bypassing the plasma membrane c. elevates cytosolic concentrations of cyclic AMP d. causes lower blood glucose by binding to liver cells

c. elevates cytosolic concentrations of cyclic AMP

In signal transduction, phosphatases _____. a. prevent a protein kinase from being reused when there is another extracellular signal b. amplify the second messengers such as cAMP c. inactivate protein kinases and turn off the signal transduction d. move the phosphate group of the transduction pathway to the next molecule of a series

c. inactivate protein kinases and turn off the signal transduction

Which of the following would be inhibited by a drug that specifically blocks the addition of phosphate groups to proteins? a. adenylyl cyclase activity b. ligand-gated ion channel signaling c. receptor tyrosine kinase activity d. G protein-coupled receptor binding

c. receptor tyrosine kinase activity

Consider this pathway: epinephrine → G protein-coupled receptor → G protein → adenylyl cyclase → cAMP. The second messenger in this pathway is _____.

cAMP

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

cortisol passes through the plasma membrane into the cytoplasm, cortisol-receptor complex forms in the cytoplasm, cortisol-receptor complex enters the nucleus where it binds to genes, cortisol-receptor complex acts as a transcription factor, the transcribed mRNA is translated into a specific protein

Which of these acts as a second messenger? protein kinase G protein adenylyl kinase cyclic AMP G-protein-linked receptor

cyclic AMP

two common second messengers

cyclic AMP and calcium ions

What role does a transcription factor play in a signal transduction pathway? a. By binding to a plasma membrane receptor it initiates a cascade. b. It relays a signal from the cytoplasm to the plasma membrane. c. It activates relay proteins. d. By binding to DNA it triggers the transcription of a specific gene. e. It is a plasma membrane protein that binds signal molecules.

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

_____ catalyzes the production of _____, which then opens an ion channel that releases _____ into the cell's cytoplasm. a. Protein kinase ... PIP2 ... Na+ b. Adenylyl cyclase ... cyclic AMP ... Ca2+ c. Adenylyl cyclase ... IP3 .... Ca2+ d. Phospholipase C ... IP3 .... Ca2+ e. Phospholipase C ... cyclic AMP ... Ca2+

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

Which of the following statements is true of signal molecules? a. When signal molecules first bind to receptor tyrosine kinases, the receptors phosphorylate a number of nearby molecules. b. In most cases, signal molecules interact with the cell at the plasma membrane, enter the cell, and eventually enter the nucleus. c. In response to some G protein-mediated signals, a special type of lipid molecule associated with the plasma membrane is cleaved to form IP3 and calcium. d. Protein kinase A activation is one possible result of signal molecules binding to G protein-coupled receptors.

d. Protein kinase A activation is one possible result of signal molecules binding to G protein-coupled receptors.

Why can a signaling molecule cause different responses in different cells? View Available Hint(s) a. Different cells have membrane receptors that bind to different sides of the signaling molecule. b. The transduction pathway in cells has a variable length. c. Different cells possess different enzymes, which modify the signaling molecule into different molecules after it has arrived. d. The transduction process is unique to each cell type; to respond to a signal, different cells require only a similar membrane receptor. e. All of the above are correct.

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

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because they _____. a. counter the harmful effects of phosphatases b. always lead to the same cellular response c. are species specific d. amplify the original signal many times

d. amplify the original signal many times

Which of the following amino acids are most frequently phosphorylated by protein kinases in the cytoplasm during signal transduction? a. glycine and histidine b. tyrosines c. glycine and glutamic acid d. serine and threonine

d. serine and threonine

Which of the following sequences is correct? View Available Hint(s) a. binding of a signaling molecule to its receptor → G protein activation → adenylyl cyclase activation → cAMP production → protein phosphorylation b. binding of a growth factor to its receptor → phosphorylation cascade → activation of transcription factor → transcription c. 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 d. binding of a signaling molecule to its receptor → G protein activation → phospholipase C activation → IP3 production → increase in cytoplasmic calcium concentration e. All of the choices are correct.

e

Which of these is NOT correct? a. Tyrosine-kinase receptors consist of two polypeptides that join when activated by a signal molecule. b. Ion channels are found on both the plasma membrane and the endoplasmic reticulum. c. Kinases are enzymes that phosphorylate other molecules. d. Phospholipase C catalyzes the formation of IP3. e. Cyclic AMP binds to calmodulin.

e. Cyclic AMP binds to calmodulin.

What is the function of tyrosine-kinase receptors? View Available Hint(s) a. enzymatic hydrolyzing of the signaling molecule shortly after its arrival b. enzymatic degrading of GTP to GDP c. binding to nonpolar signaling molecules such as nitric oxide or the steroid hormones d. allowing specific ions to enter the cell after ligand binding e. enzymatic phosphorylation of tyrosine in the receptor protein

e. enzymatic phosphorylation of tyrosine in the receptor protein

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

endoplasmic reticula

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

paracrine signaling

Three stages of cell signaling

reception, transduction, response

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.

reception: signaling molecule, g-protein coupled receptor, receptor tyrosine kinase transduction: adenylyl cyclase, phosphorylation cascade, second messenger, Ca+2, cAMP, IP3 response: protein synthesis

One of the major categories of receptors in the plasma membrane reacts by forming dimers, adding phosphate groups, and then activating relay proteins. Which type does this?

receptor tyrosine kinases

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

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?

signal molecule

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.

steroid

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? enhancers growth factor receptors nucleosomes transcription factors DNA polymerases

transcription factors