ch 9 cell communication

The system of communication between cells through signaling pathways is called homeostasis.

a. True

b. False

b. False

 In the liver, the enzyme glycogen phosphorylase catalyzes the breakdown of glucose.

a. True

b. False

b. False

Steroid hormones, such as testosterone and estrogen, are polar signaling molecules

a. True

b. False

b. False

After the binding of a signaling molecule to a surface receptor, the signaling molecule does not enter the cell.

a. True

b. False

a. True

After signal transduction has run its course, receptor molecules are removed from the surface by endocytosis; one

possible fate of the receptor is to be separated from its signaling molecule and returned to the cell surface.

a. True

b. False

a. True

G-protein-coupled receptors are found in both prokaryotes and eukaryotes.

a. True

b. False

b. False

 In plants, the IP3/DAG pathways control the organism's responses to water loss and changes in light intensity.

a. True

b. False

True

Steroid hormones are nonpolar molecules derived from cholesterol.

a. True

b. False

True

In breast cancer, ERα is often lost, which increases cell proliferation.

a. True

b. False

False

Cross-talk between second messenger pathways is probably involved in particular types of olfactory signal

transduction in many animals.

a. True

b. False

True

 In order for a target cell to receive a signal, it must possess a

____ specific to the signaling molecule.

a. glycolipid

b. glycoprotein

c. receptor

d. transfer protein

e. hormone

c. receptor

 Adjacent animal cells utilize

____

to rapidly communicate with each other.

a. gap junctions

b. plasmodesmata

c. hormones

d. desmosomes

e. neurotransmitters

a. gap junctions

Adjacent plant cells utilize

____

to rapidly communicate with each other.

a. gap junctions

b. plasmodesmata

c. transport proteins

d. desmosomes

e. neurotransmitters

b. plasmodesmata

 How do cells in the body of a multicellular organism communicate with each other?

a. by way of signaling molecules that interact with specific receptors

b. through long projections that directly connect cells to each other

c. through electrical signals passed between a cell and its external environment

d. by the transport of ions between cells in different parts of the organism

e. by the transport of ions in water

a. by way of signaling molecules that interact with specific receptors

Substance B is synthesized in neurons, travels through gap junctions, and triggers the transduction of an

electrochemical signal. This is an example of ____.

a. autocrine signaling

b. paracrine signaling

c. long-distance signaling

d. local signaling

e. communication by direct contact

e. communication by direct contact

Substance A is synthesized in the liver, travels through the circulatory system bound to a carrier protein, and causes a

change in gene expression in a target cell. This is an example of ____.

a. autocrine signaling

b. paracrine signaling

c. long-distance signaling

d. local signaling

e. communication by direct contact

c. long-distance signaling

In order for a cell to respond to the signaling molecule epinephrine, it must have ____.

a. ion channels

b. a lipid bilayer through which epinephrine can pass

c. receptors with an epinephrine binding site on the cytoplasmic side of the plasma membrane

d. receptors with an epinephrine binding site on the plasma membrane surface

e. nuclear membrane receptors

d. receptors with an epinephrine binding site on the plasma membrane surface

 Receptors for polar molecules are found ____, while receptors for nonpolar molecules are located ____.

a. on the cell surface; within the cell

b. within the cell; on the cell surface

c. on the cell surface; on the nuclear membrane

d. on the nuclear membrane; on the cell surface

e. on the cell surface; within the lipid bilayer

a. on the cell surface; within the cell

Nonpolar signaling molecules enter the cell by ____.

a. facilitated diffusion

b. simple diffusion

c. osmosis

d. active transport

e. receptor-mediated endocytosis

b. simple diffusion

An example of a nonpolar signaling molecule is ____.

a. epinephrine

b. insulin

c. testosterone

d. growth factors

e. neurotransmitters

c. testosterone

How does a cell surface receptor respond to the binding of a signaling molecule?

a. The cell surface receptor denatures.

b. The signal is transduced through the plasma membrane and into the cell.

c. The receptor relays a signal to another location on the cell surface.

d. The cell surface receptor flips through the membrane to the inside of the cell.

e. Polarization of the cell surface changes.

b. The signal is transduced through the plasma membrane and into the cell.

The overall process by which information carried by a signaling molecule is translated into changes that occur inside

the cell is called signal ____.

a. digestion

b. digression

c. induction

d. interaction

e. transduction

e. transduction

 You have recently identified a molecule you believe to be a signaling molecule associated with signal transduction.

All you know about this molecule is that it is hydrophilic; therefore, you expect it to interact with a receptor ____.

a. on the cell surface

b. within the cytoplasm of the cell

c. in the nucleus of the cell

d. on the cytoplasmic surface of the plasma membrane

e. associated with the endoplasmic reticulum

a. on the cell surface

. In the 1950s, Earl Sutherland and colleagues discovered that epinephrine ____.

a. triggers the release of a second messenger which leads to the hydrolysis of glycogen to glucose

b. triggers the release of a second messenger which lowers blood glucose by causing it to bind to liver cells

c. interacts directly with the enzyme glycogen phosphorylase

d. interacts directly with the cell membrane to help transport glucose into the cell

e. is a signaling molecule that does not require a cell surface receptor

a. triggers the release of a second messenger which leads to the hydrolysis of glycogen to glucose

In general, a cell receiving a message undergoes three stages of cell signaling. What are these stages?

a. paracrine, autocrine, and local

b. signal reception, signal transduction, and cellular response

c. signal reception, nucleus disintegration, and apoptosis

d. signal reception, cellular response, and cell division

e. the alpha, beta, and gamma

b. signal reception, signal transduction, and cellular response

A pathway for cell growth control is conserved between Drosophila and humans, indicating that the pathway is ____.

a. also found in prokaryotes

b. also found in all animals

c. at least 800 million years old

d. at least 3.8 billion years old

e. at least 8 million years old

c. at least 800 million years old

 In the process of quorum sensing, bacteria release signaling molecules in

____

concentrations as cell density ____.

a. increasing; decreases

b. increasing; increases

c. decreasing; increases

d. decreasing; decreases

e. constant; increases

b. increasing; increases

Quorum sensing ____.

a. allows receptors from different parts of the cell to work together to elicit a response

b. allows receptors from different parts of the body to work together to elicit a response

c. uses multiple cellular pathways to elicit a specific response

d. is a type of communication between unicellular organisms

e. is a type of cell communication between multicellular organisms

d. is a type of communication between unicellular organisms

The evolution of which class of molecules played an important role in the development of multicellular organisms?

a. G proteins

b. protein kinases

c. second messengers

d. ligand-gated ion channels

e. steroid hormones

b. protein kinases

The two major categories of extracellular signaling molecules that bind to cell surface receptors are ____.

a. peptide hormones and steroid hormones

b. steroid hormones and neurotransmitters

c. neurotransmitters and vitamins

d. growth hormones and vitamins

e. peptide hormones and neurotransmitters

e. peptide hormones and neurotransmitters

Neurotransmitters are molecules released by ____.

a. gonads

b. polar hormones

c. peptide hormones

d. cells in the blood

e. neurons

e. neurons

The surface receptors that recognize and bind signaling molecules are ____.

a. glycoproteins

b. glycolipids

c. phospholipids

d. promoters

e. ligands

a. glycoproteins

The recognition of a chemical signal by a receptor protein in the membrane is most similar to ____.

a. mRNA specifying the sequence of amino acids in a polypeptide

b. binding of a specific substrate to the active site of an enzyme

c. turning on gene transcription

d. allosteric regulation of proteins

e. an enzyme requiring a specific optimum pH and temperature for activity

b. binding of a specific substrate to the active site of an enzyme

The last protein in a signaling pathway is called the ____.

a. target protein

b. final acceptor

c. electron acceptor

d. second messenger

e. effector protein

a. target protein

 Amplification of a signal increases as the ____.

a. number of enzyme-catalyzed steps increases

b. number of enzyme-catalyzed steps decreases

c. volume of the cell increases

d. volume of the cell decreases

e. rate of reaction of the rate-limiting reaction increases

a. number of enzyme-catalyzed steps increases

 In the first step of signal transduction, what is the trigger for the cellular response?

a. target protein

b. kinase

c. ligand

d. second messenger

e. effector

c. ligand

What is the second step of signal transduction?

a. reception

b. transduction

c. differentiation

d. division

e. response

b. transduction

 Protein kinases ____.

a. add phosphate groups to proteins

b. bind cGMP

c. stimulate adenylyl cyclase

d. polymerize amino acids

e. hydrolyze proteins

a. add phosphate groups to proteins

 The effects of protein kinases are reversed by another group of enzymes called ____.

a. hydrolases

b. catalases

c. isomerases

d. phosphatases

e. proteases

d. phosphatases

Once transduction of a signal is complete, the receptor and its bound signaling molecule are removed from the cell

surface by ____.

a. hydrolysis

b. diffusion

c. endocytosis

d. pinocytosis

e. exocytosis

c. endocytosis

The protein kinase activity of the receptor tyrosine kinase (RTK) is located

____ region of the protein.

a. on the extracellular

b. on the cytoplasmic

c. within the hydrophobic

d. in the nuclear

e. in the inactive

b. on the cytoplasmic

During autophosphorylation, RTKs add phosphate groups to which amino acids?

a. serine

b. glycine

c. threonine

d. tryptophan

e. tyrosine

e. tyrosine

What happens immediately after a signaling molecule binds to an RTK?

a. receptor dimerization

b. receptor trimerization

c. receptor denaturation

d. receptor polymerization

e. receptor hydrolysis

a. receptor dimerization

Structurally similar RTKs have been found in all multicellular animals, suggesting that ____.

a. RTK genes are resistant to mutation

b. RTKs evolved relatively early in the history of animals

c. RTKs evolved from G proteins

d. RTKs are not involved in vital processes in animals

e. RTKs have evolved independently of each other in animals

b. RTKs evolved relatively early in the history of animals

The insulin receptor is an example of a(n) ____.

a. G-protein-coupled receptor

b. hydrophobic receptor

c. hormone receptor

d. receptor tyrosine kinase

e. ion channel receptor

d. receptor tyrosine kinase

 Substance E is made in the pancreas, travels through the blood, and binds to a surface receptor on a target cell. After

dimerization and autophosphorylation, the receptor activates a signaling protein. Substance E is therefore the ligand for

____.

a. a receptor tyrosine kinase

b. a G-protein-coupled receptor

c. a hormone receptor

d. a ligand-gated ion channel

e. guanylyl cyclase

a. a receptor tyrosine kinase

Arrange the events in the pathway activated by G-protein-coupled receptors (GPCRs) in the correct order.

1. Activation of effector

2. Activation of protein kinases

3. Receptor binds first messenger

4. Production of second messenger

5. Activation of G protein

a. 1→3→5→2→4

b. 2→3→5→4→1

c. 3→1→5→4→2

d. 3→5→1→4→2

e. 3→5→2→4→1

d. 3→5→1→4→2

Inactive G proteins are ____.

a. bound to GMP

b. bound to GDP

c. bound to GTP

d. phosphorylated

e. unphosphorylated

b. bound to GDP

Activated G proteins ____.

a. trigger endocytosis of the G-protein-coupled receptor

b. bind to second messengers

c. separate into two parts

d. activate a kinase

e. inhibit guanylyl cyclase

c. separate into two parts

How many transmembrane domains are present in a G-protein-coupled receptor?

a. one

b. three

c. five

d. seven

e. nine

d. seven

 Many of the different types of GPCRs in humans function to ____.

a. distinguish different volatile molecules for odor recognition

b. regulate metabolism by sensing and responding to changes in glucose levels

c. regulate liver function by responding to different macromolecules

d. aid in memory by binding to neurotransmitters in the amygdala

e. trigger the fight of flight response by binding to hormones in the hypothalamus

a. distinguish different volatile molecules for odor recognition

More than 60% of all prescribed drugs target ____, due to their wide physiological impact.

a. receptor tyrosine kinases

b. hormone receptors

c. guanylyl cyclase

d. ligand-gated ion channels

e. G-protein-coupled receptors

e. G-protein-coupled receptors

 G proteins are inactivated when ____.

a. GDP is converted to GTP

b. GTP is converted to GDP

c. the G protein rebinds the receptor

d. the G protein is released from the receptor

e. the receptor is broken down

b. GTP is converted to GDP

Many signal transduction pathways utilize second messengers to ____.

a. transport a signal through the lipid bilayer of the plasma membrane

b. relay a signal from the outside of the cell to the inside

c. relay a signal from the inside of the cell to the outside

d. decrease the message once the signaling molecules have left the receptor

e. relay the message from the inner surface of the plasma membrane throughout the cytoplasm

e. relay the message from the inner surface of the plasma membrane throughout the cytoplasm

The amino acid targets of protein kinases in all GPCR pathways are ____.

a. serine and glycine

b. serine and tyrosine

c. serine and threonine

d. glycine and tyrosine

e. glycine and threonine

c. serine and threonine

Which molecule is a common second messenger?

a. cGTP

b. cATP

c. PIP2

d. diacylglycerol

e. Ras

d. diacylglycerol

 In the cAMP pathway, the G protein activates ____.

a. adenylyl cyclase

b. diacylglycerol

c. phospholipase C

d. inositol triphosphate

e. phosphodiesterase

a. adenylyl cyclase

Once activated, cAMP is quickly degraded to AMP by ____, switching off the signal pathway.

a. adenylyl cyclase

b. diacylglycerol

c. phospholipase C

d. acetylcholinesterase

e. phosphodiesterase

e. phosphodiesterase

In the IP3/DAG pathway, what is the effector molecule?

a. IP3

b. DAG

c. PIP2

d. phospholipase C

e. calcium

d. phospholipase C

 Substance C is secreted from a neuron, and binds to its receptor on a nearby cell, triggering an increase in intracellular

cAMP. Substance C is therefore a ligand for a ____.

a. a receptor tyrosine kinase

b. a G-protein-coupled receptor

c. a hormone receptor

d. a ligand-gated ion channel

e. guanylyl cyclase

b. a G-protein-coupled receptor

Ras proteins are of interest to researchers because of their role in ____.

a. reproduction

b. linking plant hormones to germination

c. the development of many types of cancer

d. relieving cluster headaches

e. eliciting the fight-or-flight response

c. the development of many types of cancer

 Inactive Ras is bound to receptor tyrosine kinases by ____.

a. G proteins

b. adapter proteins

c. phosphate bonds

d. peptide tethers

e. GDP

b. adapter proteins

Activated Ras ____.

a. activates MAP kinase (MAP K)

b. opens a calcium channel

c. triggers gene transcription

d. binds DNA

e. triggers the secretion of growth factors

a. activates MAP kinase (MAP K)

Acetylcholine, a neurotransmitter, binds to ____.

a. receptor tyrosine kinases

b. ligand-gated ion channels

c. adenylyl cyclase

d. MAPK

e. G-coupled protein receptors

b. ligand-gated ion channels

 Which cellular response follows activation of a ligand-gated ion channel?

a. direct regulation of gene expression

b. generation of an electrical signal

c. activation of a phosphorylation cascade

d. activation of a second messenger pathway

e. direct activation of a kinase

b. generation of an electrical signal

 A neuron synthesizes and secretes substance D, which binds to a receptor on the neuron cell membrane, triggering an

influx of calcium. Substance D therefore is a ligand for a ____.

a. a receptor tyrosine kinase

b. a G-protein-coupled receptor

c. a hormone receptor

d. a ligand-gated ion channel

e. guanylyl cyclase

d. a ligand-gated ion channel

 Steroid and thyroid hormones do not bind to membrane surface receptors because they ____.

a. are small enough to pass directly through the membrane

b. are soluble in the lipid bilayer

c. pass through special membrane channels

d. are water-soluble

e. dissolve in the cholesterol present in cell membranes

b. are soluble in the lipid bilayer

Steroid hormones ____.

a. are proteins

b. include testosterone, estrogens, and cortisol

c. never activate second messengers

d. never alter membrane transport of ions

e. are large nonpolar molecules

b. include testosterone, estrogens, and cortisol

Why are steroid hormones bound to carrier proteins in the blood?

a. to prevent them from entering non-target cells

b. to keep them in an inactivate state

c. to mask hydrophobic groups on the steroids to allow for circulation in the blood

d. to help them bind to surface receptors and trigger a cellular response

e. to help them bind to surface receptors and trigger endocytosis

c. to mask hydrophobic groups on the steroids to allow for circulation in the blood

 How do cells distinguish between estrogen and testosterone?

a. only male cells respond to testosterone and female cells respond to estrogen

b. estrogen is hydrophilic and binds to surface receptors, while testosterone is hydrophobic and binds to internal

receptors

c. estrogen and testosterone have similar functional groups but different basic structures that are easily

distinguished by their individual receptors

d. estrogen and testosterone have the same basic structures, but different side chains that are easily distinguished

by their individual receptors

e. estrogen and testosterone bind to different carrier proteins, which help receptors distinguish between the two

molecules

d. estrogen and testosterone have the same basic structures, but different side chains that are easily distinguished

Estrogen receptor (ER) α typically ____, while ERβ typically ____.

a. stimulates DNA binding; inhibits DNA binding

b. stimulates cell proliferation; inhibits cell proliferation

c. stimulates channel opening; inhibits channel opening

d. inhibits DNA binding; stimulates DNA binding

e. inhibits cell proliferation; stimulates cell proliferation

b. stimulates cell proliferation; inhibits cell proliferation

 Researchers have determined that the growth of hormone-responsive breast cancer cells depends upon ____.

a. the relative concentrations of ERα and ERβ in the tumor cells

b. the ability of ERβ to stimulate cancer cell growth

c. the ability of ERα to inhibit cancer cell growth

d. whether DNA binding sites exists for ERα, but not ERβ

e. the relative concentrations of estrogen and testosterone in brea

a. the relative concentrations of ERα and ERβ in the tumor cells

Hormone receptors are comprised of two domains, the hormone binding domain and the ____, which triggers the

cellular response.

a. gene activation domain

b. DNA-binding domain

c. phosphorylation domain

d. kinase domain

e. phosphatase domain

b. DNA-binding domain

 Substance A is secreted by the liver, travels through the circulatory system bound to a carrier protein and causes a

change in gene expression in its target cell. Substance A is therefore a ligand for ____.

a. a receptor tyrosine kinase

b. a G-protein-coupled receptor

c. a steroid hormone receptor

d. a ligand-gated ion channel

e. guanylyl cyclase

c. a steroid hormone receptor

Nitric oxide (NO) binds to an ____.

a. internal receptor and activates a second messenger cascade

b. internal receptor and triggers a phosphorylation cascade

c. external receptor and activates a second messenger cascade

d. external receptor and triggers a phosphorylation cascade

e. external receptor and opens a ligand-gated ion channel.

a. internal receptor and activates a second messenger cascade

 NO can only function as a paracrine regulator because____.

a. it is hydrophilic and cannot travel free in the blood

b. it is hydrophobic and cannot travel free in the blood

c. it is rapidly converted into nitrates and nitrites

d. its receptors are rapidly turned over

e. its receptors are immediately internalized when the ligand binds

c. it is rapidly converted into nitrates and nitrites

How is the NO pathway manipulated by Viagra to treat erectile dysfunction?

a. NO synthesis is decreased

b. NO synthesis is increased

c. the enzyme catalyzed by NO is stabilized

d. the enzyme catalyzed by NO is inhibited

e. the breakdown of cGMP is inhibited

e. the breakdown of cGMP is inhibited

 NO binds to and activates____ to trigger its cellular response.

a. receptor tyrosine kinase

b. G-protein coupled receptors

c. MAPK

d. adenylyl cyclase

e. guanylyl cyclase

e. guanylyl cyclase

 Communication and integration of responses between simultaneously occurring cell signaling pathways is called

____.

a. mutualistic responding

b. effector coordination

c. cross-talk

d. amplification

e. signal transduction

c. cross-talk

 Hormone-independent steroid hormone receptor activation is an example of ____.

a. allosteric activation

b. gene regulation

c. receptor integration

d. protein mutation

e. cross-talk

e. cross-talk