Deck 9: Cell Communication

Question 1

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

Answer 1

False

Question 2

Steroid hormones are nonpolar molecules derived from cholesterol.

Answer 2

True

Question 3

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

Answer 3

C

Question 4

Adjacent animal cells utilize ____ to rapidly communicate with each other.

A) gap junctions
B) plasmodesmata
C) hormones
D) desmosomes
E) neurotransmitters

Question 5

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

Question 6

Adjacent plant cells utilize ____ to rapidly communicate with each other.

A) gap junctions
B) plasmodesmata
C) transport proteins
D) desmosomes
E) neurotransmitters

Question 7

An example of a nonpolar signaling molecule is ____.

A) epinephrine
B) insulin
C) testosterone
D) growth factors
E) neurotransmitters

Question 8

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

Question 9

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

Question 10

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

Question 11

Nonpolar signaling molecules enter the cell by ____.

A) facilitated diffusion
B) simple diffusion
C) osmosis
D) active transport
E) receptor-mediated endocytosis

Question 12

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

Question 13

An active phosphatase adds phosphate groups to other molecules.

Question 14

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

Question 15

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

Question 16

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

Question 17

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

Question 18

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

Question 19

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

Question 20

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

Question 21

Neurotransmitters are molecules released by ____.

A) gonads
B) polar hormones
C) peptide hormones
D) cells in the blood
E) neurons

Question 22

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

A) hydrolases
B) catalases
C) isomerases
D) phosphatases
E) proteases

Question 23

Cell signaling pathways evolved ____.

A) thousands of years ago
B) in multicellular organisms
C) hundreds of millions of years ago
D) tens of billions of years ago
E) 1 million years ago

Question 24

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

Question 25

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

Question 26

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

A) triggers the release of a second messenger that leads to the hydrolysis of glycogen to glucose
B) triggers the release of a second messenger that 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

Question 27

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

Question 28

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

Question 29

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

Question 30

What is the second step of signal transduction?

A) reception
B) transduction
C) differentiation
D) division
E) response

Question 31

Dictyostelium amoebas gather to form a fruiting body in a process similar to ____.

A) G-protein-coupled signaling
B) quorum sensing
C) a phosphorylation cascade
D) paracrine signaling
E) autocrine signaling

Question 32

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.

Question 33

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

Question 34

Protein kinases ____.

A) add phosphate groups to proteins
B) bind cGMP
C) stimulate adenylyl cyclase
D) polymerize amino acids
E) hydrolyze proteins

Question 35

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

Question 36

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

Question 37

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

A) glycoproteins
B) glycolipids
C) phospholipids
D) promoters
E) ligands

Question 38

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

Question 39

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

Question 40

Signaling molecules bind to the ____ region of a receptor tyrosine kinase.

A) intracellular
B) hydrophobic
C) extracellular
D) cytoplasmic
E) intramembrane

Question 41

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

Question 42

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

Question 43

Which molecule is a common second messenger?

A) cGTP
B) cATP
C) PIP₂
D) diacylglycerol
E) Ras

Question 44

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

Question 45

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

Question 46

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

Question 47

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

Question 48

In the cAMP pathway, the G protein activates ____.

A) adenylyl cyclase
B) diacylglycerol
C) phospholipase C
D) inositol triphosphate
E) phosphodiesterase

Question 49

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

A) one
B) three
C) five
D) seven
E) nine

Question 50

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

A) IP₃
B) DAG
C) PIP₂
D) phospholipase C
E) calcium

Question 51

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

Question 52

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

Question 53

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

Question 54

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

Question 55

Inactive G proteins are ____.

A) bound to GMP
B) bound to GDP
C) bound to GTP
D) phosphorylated
E) unphosphorylated

Question 56

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

A) serine
B) glycine
C) threonine
D) tryptophan
E) tyrosine

Question 57

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

Question 58

Arrange the events in the pathway activated by G-protein-coupled receptors (GPCRs) in the correct order.
Activation of effector
Activation of protein kinases
Receptor binds first messenger
Production of second messenger
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

Question 59

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

Question 60

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

Question 61

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

Question 62

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

Question 63

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

Question 64

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

Question 65

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

Question 66

Inactive Ras is bound to receptor tyrosine kinases by ____.

A) G proteins
B) adapter proteins
C) phosphate bonds
D) peptide tethers
E) GDP

Question 67

How do cells distinguish between estrogen and testosterone?

A) Only male cells respond to testosterone, and female cells respond to estrogen.
B) Eestrogen is hydrophilic and binds to surface receptors, while testosterone is hydrophobic and binds to internal receptors.
C) Eestrogen 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.

Question 68

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

Question 69

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

Question 70

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

Question 71

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

Question 72

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

Question 73

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.

Question 74

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

Question 75

Acetylcholine, a neurotransmitter, binds to ____.

A) receptor tyrosine kinases
B) ligand-gated ion channels
C) adenylyl cyclase
D) MAPK
E) G-coupled protein receptors

Question 76

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

Question 77

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

Question 78

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

Question 79

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

Question 80

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 breast tissue