Deck 9: Cell Communication

Question 1

Enzymatic receptors typically activate intracellular proteins by ____________.

A)charging
B)energy
C)binding
D)phosphorylation

Answer 1

D

Question 2

A small number of surface receptors can ultimately generate a large intracellular response,as each step of the pathway is often expanded by signal _________.

A)amplification
B)transduction
C)dampening
D)splitting

Answer 2

A

Question 3

All of the following statements about chemically-gated ion channels are true except

A)their amino acid chains wind back and forth across the membrane.
B)they close in response to binding of the signal molecule.
C)a pore exists in the center of the protein.
D)the pore connects the extracellular fluid with the cytoplasm.
E)the pore is big enough for ions to pass through it.

Answer 3

B

Question 4

Adjacent cells can signal others by direct contact,while nearby cells that are not touching can communicate by the release of __________ signals.

A)autocrine
B)neurosecretory
C)peptide
D)paracrine

Question 5

Endocrine signaling involves the release of __________.

A)neurotransmitters
B)hormones
C)peptides
D)cells

Question 6

Hormones are an example of intercellular communication known as _____________ signaling.

A)neural
B)endocrine
C)paracrine
D)autocrine

Question 7

Tight and anchoring _______ cause cells to adhere tightly to each other.

A)cells
B)proteins
C)signals
D)junctions

Question 8

Synaptic signaling requires which of the following to be released into the synaptic gap?

A)hormones
B)internal receptors
C)genes
D)neurotransmitters
E)lipids

Question 9

Signals with short-lived,local effects are called

A)direct contact.
B)endocrine signals.
C)paracrine signals.
D)synaptic signals.
E)light signals.

Question 10

The molecules that convert extracellular signals into intracellular ones are

A)neurotransmitters.
B)peptide hormones.
C)cell surface receptors.
D)growth factor proteins.
E)genes.

Question 11

Chemically-gated ion ________ open or close when signal molecules bind to the channel,allowing specific ions to diffuse through the channel.

A)channels
B)molecules
C)species
D)membranes

Question 12

Located on or within the cell are _________ proteins,each of which has a three dimensional shape complementary to that of a specific signal molecule.

A)amplification
B)monoclonal
C)transmembranal
D)receptor
E)messenger

Question 13

The class of cell surface receptors that acts indirectly on plasma membrane-bound enzymes or ion channels is called

A)G-protein-coupled receptors.
B)gated ion channels.
C)enzymatic receptors.
D)second messenger receptors.

Question 14

___________ among cells is a hallmark of multicellular organisms.

A)Communication
B)Transport
C)Linkage
D)Identity

Question 15

Specific protein receptors are present for all of the following except

A)signal amplification.
B)signal transduction.
C)intracellular receptors binding to DNA.
D)signaling to other cells.
E)cell junctions.

Question 16

Which of the following is considered to be a second messenger?

A)cAMP
B)Ca⁺⁺ ions
C)diacyl glycerol (DAG)
D)inositol-1,4,5-triphosphate (IP₃)
E)phospholipase C

Question 17

The space into which neurotransmitters are released is called a chemical

A)synapse.
B)junction.
C)channel.
D)desmosome.
E)vesiclE.

Question 18

Protein kinases,enzymes which add phosphate groups to proteins,are an example of ______________ receptors.

A)enzymatic
B)extracellular
C)phosphogenic
D)ATP

Question 19

Signal molecules activate intracellular receptors in

A)chromosomes.
B)vesicles.
C)target cells.
D)skin cells.
E)surface cells.

Question 20

Communication between cells can occur by all of the following basic mechanisms except

A)direct contact.
B)intracellular signaling.
C)paracrine signaling.
D)endocrine signaling.
E)synaptic signaling.

Question 21

A researcher is investigating several MHC proteins.That means she is

A)studying proteins similar to G-protein-coupled receptors.
B)studying proteins that provide surface markers for distinguishing between "self" and "non-self" cells.
C)studying proteins that are commonly used to detect human blood groups (A,B,AB,and O).
D)studying proteins that act as second messengers.

Question 22

A biochemist is designing a new drug that will mimic the shape and function of a particular signal molecule.Therefore she must produce a molecule that will bind to the receptor protein and

A)induce a change in the receptor molecule shape,which will ultimately prevent a cellular response.
B)induce a change in the receptor molecule shape,which will ultimately produce a cellular response.
C)induce a change in the phospholipid bilayer that causes a polar reversal allowing the molecules to be endocytosed.
D)produce a cellular response by altering the Na⁺/K⁺ pump located near the receptor site.

Question 23

What characteristics do all cell surface receptors share?

A)They are composed of hydrophilic proteins.
B)They all must bind to a molecule to be activated.
C)They all result in creation of an ion channel.
D)They include the activation of a G protein.

Question 24

Some enzymatic receptors and most G-protein-coupled receptors carry the signal molecule's message into the target cell by utilizing other substances within the cytoplasm commonly called

A)genes.
B)intracellular receptors.
C)enzymes.
D)second messengers.
E)first messengers.

Question 25

Which pair are examples of second messengers?

A)sodium,potassium ions
B)amino acids,proteins
C)steroids,lipids
D)sugars,starches
E)cAMP,calcium ions

Question 26

In the digestive tract adjacent cells develop connections to form a sheet that prevents leakage of small molecules.These connections between cells are called

A)communicating junctions.
B)desmosomes.
C)gap junctions.
D)ion gates.
E)tight junctions.

Question 27

A team of researchers at a pesticide company are working produce a new rodent poison to address a growing problem of rat infestations at an old waterfront warehouse.The researchers are developing a poison that will cause the junctions between intestinal cells to break down.The poison will be incorporated into grain and left where the rodents will feed on it.Which of the following describes the most likely effect of this poison?

A)The gap junctions will break down resulting in leaks in the digestive tract.
B)The tight junctions will break down resulting in leaks in the digestive tract.
C)The gap junctions will break down and interfere with absorption of nutrients.
D)The tight junctions will break down and interfere with absorption of nutrients.

Question 28

You are having lunch with an elderly friend when suddenly he begins to experience chest pain and tightness.He reaches into his pocket,gets out one of his nitroglycerin tablets and quickly takes it.After the episode passes,your friend asks you how the nitroglycerin helps his angina.You explain that nitroglycerin gets converted by cells to NO causing the smooth muscle cells of the blood vessel to relax and increase blood flow to the heart.He pushes you for a more detailed explanation,so you explain further that

A)NO activates guanylyl cyclase,which catalyzes the synthesis of cGMP,which acts as an intracellular messenger in a pathway leading to smooth muscle relaxation.
B)NO activates a protein kinase which catalyzes the synthesis of cGMP,which acts as an intracellular messenger in a pathway leading to smooth muscle relaxation.
C)NO inhibits guanylyl cyclase,which allows the build up of cGMP,which acts as an intracellular messenger in a pathway leading to smooth muscle relaxation.
D)NO activates cGMP,which catalyzes the synthesis of guanylyl cyclase,which acts as an intracellular messenger in a pathway leading to smooth muscle relaxation.

Question 29

A small number of surface receptors can ultimately generate a large intracellular response,as each step of the pathway is often expanded by

A)enzymatic receptors.
B)gated ion channels.
C)signal amplification.
D)G-protein-coupled receptors.

Question 30

Signal molecules on a cell membrane interact with molecules on a neighboring cell membrane.

A)paracrine signaling
B)direct contact
C)endocrine signaling
D)synaptic signaling

Question 31

Long-lived;affects cells very distant from the releasing cell.

A)paracrine signaling
B)direct contact
C)endocrine signaling
D)synaptic signaling

Question 32

Which of the following is not part of the cell communication system in animal cells?

A)gap junctions
B)plasmodesmata
C)tight junctions
D)desmosomes

Question 33

A researcher is trying to produce a new cancer drug to be tested on small tumors.The tumor has to be localized in a small area of the body and cannot have metastasized (spread to other areas of the body).Furthermore,this drug must prohibit the signaling from one tumor cell to another tumor cell.Given the above information,this new drug will prohibit

A)direct physical contact between tumor cells.
B)autocrine signaling between tumor cells.
C)paracrine signaling between tumor cells.
D)endocrine signalizing between tumor cells.

Question 34

Which of following statements about G proteins associated with G-protein-coupled receptors is false?

A)G proteins provide a link between the receptor and effector protein.
B)G proteins can propagate the signal by either the G _$\alpha$ or the G _{$\beta$ $\gamma$} components.
C)G proteins are heterotrimeriC.
D)Associated G proteins become active by exchanging GTP for GDP.
E)Activated G protein diffuses away from the receptor.

Question 35

G-protein-coupled receptors are the largest family of cell surface receptors.Each receptor passes through the plasma membrane

A)three times.
B)four times.
C)five times.
D)six times.
E)seven times.

Question 36

Some plant cells have their cytoplasms linked,which permits small molecules and ions to pass from one cell to the other.These areas of cytoplasmic linkages are called

A)gap junctions.
B)anchoring junctions.
C)tight junctions.
D)plasmodesmata.
E)adherens junctions.

Question 37

Chemically-gated ion channels are receptor proteins through which ions pass.A cell biologist has blocked these channels in a lab rat's liver tissue by using a chemical that

A)prohibits binding of a signal molecule.
B)prohibits ions from entering the cell via active transport.
C)causes ions to move in the opposite direction of the ion gradient.
D)prohibits second messenger signaling.

Question 38

Most cells are in physical contact with other cells at all times by forming permanent connections called

A)cell junctions.
B)gated ion channels.
C)enzymatic receptors.
D)G-protein-coupled receptors.
E)cell surface markers.

Question 39

In plants,cell-cell junctions can only occur at gaps in the cell walls through cytoplasmic connections that form across the plasma membranes of the touching cells.These junctions are called

A)desmosomes.
B)tight junctions.
C)plasmodesmata.
D)the cellulose matrix.
E)adhering junctions.

Question 40

Small molecules or ions can pass from one cell to another through

A)tight junctions.
B)gap junctions.
C)diffusion spheres.
D)desmosomes.
E)adherens junctions.

Question 41

You are performing an experiment to assay phosphorylation of a substrate by a protein kinase.Based on the data in the table below,what do these experimental results suggest?

A)GTP is not required for phosphorylation.
B)The substrate can undergo autophosphorylation.
C)The substrate is not required for phosphorylation.
D)The protein kinase is required for phosphorylation.

Question 42

You are planning to perform some protein-protein interaction studies to identify a receptor for a steroid hormone you have been working on.With which of the following types of cell extracts should you begin?

A)plasma membrane
B)extracellular
C)cytoplasmic
D)nuclear

Question 43

A mutation that affects Ca⁺⁺ binding to calmodulin is most likely to interfere with which aspect of a signal transduction pathway?

A)the flow of Ca⁺⁺ ions through ion channel receptors
B)the cellular response to the second messenger
C)MAP kinase cascade
D)G protein activity

Question 44

The protein SOS is a guanine nucleotide exchange factor for Ras.SOS helps facilitate the exchange of GDP for GTP.What would be the effect of a mutation that inhibits the interaction between SOS and Ras?

A)GTP would remain bound to Ras,thereby disrupting downstream signaling events.
B)GDP would remain bound to Ras,thereby disrupting downstream signaling events.
C)GTP would remain bound to Ras,leading to overstimulation of the Ras pathway.
D)GDP would remain bound to Ras,leading to overstimulation of the Ras pathway.

Question 45

You have identified a novel cytoplasmic protein.Sequence analysis revealed the presence of a number of serine/threonine phosphorylation motifs.Based on this data,you hypothesize that this protein may be a substrate for a

A)protein kinase.
B)receptor tyrosine kinase.
C)G-protein-coupled receptor.
D)phosphotyrosine adapter protein.

Question 46

A mutation in the DNA binding domain of a steroid hormone receptor is most likely to affect the

A)conformational change of the receptor.
B)binding of the hormone to the receptor.
C)translocation of the receptor to the nucleus.
D)cellular response to the hormone.

Question 47

The protein Sonic Hedgehog (SHH)plays a role in specifying the identity of digits (such as fingers,etc. )in mammals.Several digits arise directly from cells that both express and respond to secreted SHH.In this case,SHH is acting as

A)a direct contact signal.
B)an endocrine signal.
C)a paracrine signal.
D)an autocrine signal.

Question 48

Why is phosphorylation-dephosphorylation commonly used to regulate signal transduction pathways?

A)Phosphate groups are efficient second messengers.
B)Protein kinases and phosphatases are abundant in most cells.
C)The hydrolysis of bound GTP results in GDP and P_i.
D)The addition or removal of a phosphate group can expose or hide potential binding sites in proteins.

Question 49

Which of the following proteins phosphorylates MAP kinase kinase?

A)MAP kinase
B)MAP kinase kinase
C)MAP kinase kinase kinase
D)MAP phosphatase

Question 50

Short-lived,causing local effects.

A)paracrine signaling
B)direct contact
C)endocrine signaling
D)synaptic signaling

Question 51

You are studying the effect of a secreted signal molecule on the activity of a cytoplasmic enzyme.Prior studies have shown the signal molecule is required for enzyme activity.You add the signal molecule to a test tube solution containing both the enzyme and its substrate.After incubating the solution,you assay for the reaction product as a measure of enzyme activity,however,no product was detected.By comparison,when you add the signal molecule to a vial containing intact cells,you are able to detect the reaction product.Which of the following statements is inconsistent with these experimental results?

A)The cells express a receptor for the signal molecule.
B)There is no direct interaction between the signal molecule and enzyme.
C)The cells facilitate a direct protein-protein interaction between the signal molecule and enzyme.
D)Binding of the signal molecule to its receptor initiates a signal transduction pathway leading to enzymatic activity.

Question 52

Short lived;used by nerve cells.

A)paracrine signaling
B)direct contact
C)endocrine signaling
D)synaptic signaling

Question 53

If the effector protein phospholipase C failed to cleave phosphatidylinositol-4,5-bisphosphate (PIP₂),the action of which of the following molecules would be affected?

A)cAMP
B)calmodulin
C)protein kinase A (PKA)
D)protein kinase C (PKC)

Question 54

Vasopressin is a hormone that is primarily released when the body is low on water.Release of vasopressin causes the kidneys to conserve water by concentrating urine and decreasing urine output.However,vasopressin also has additional functions in other tissues such as the brain and blood vessels,which are not directly involved in urine production.How could it be possible for vasopressin to trigger different responses in different tissues?

A)Vasopressin can bind to,and act on,different receptor subtypes,leading to different cellular responses in different tissues.
B)Vasopressin can be released at different times to result in different effects.
C)Because vasopressin is a hormone,it can be sent to specific regions of the body leading to specific effects.

Question 55

Leptin is a hormone that is produced by fat cells and plays a role in body metabolism and obesity.Studies have demonstrated that when obese mice are injected with leptin they quickly lose their excess weight.Interestingly,however,many overweight people have high levels of leptin in their bloodstream.Which of the following explanations is most consistent with this observation?

A)Paracrine signaling may be disrupted in obese people with high levels of leptin.
B)Obese people who have high levels of leptin may have a defective leptin receptor.
C)The form of leptin released by obese people may lack protein kinase activity.
D)In obese people with high levels of leptin,the leptin is binding to the wrong receptor.

Question 56

Your research project involves the characterization of a particular signal transduction pathway.Specifically,you have been studying a receptor tyrosine kinase and protein X,which initiates downstream events.You are certain that protein X is part of the signal transduction pathway,but have been unable to identify a direct protein-protein interaction between the receptor tyrosine kinase and the protein X.What should you do next?

A)Try to identify a coactivator protein.
B)Try to identify proteins that act downstream of protein X.
C)Try to identify an adapter protein that can interact with both the receptor and protein X.
D)Confirm the interaction between the receptor tyrosine kinase and its signal molecule.

Question 57

Thyroid hormone is a steroid hormone that can exert various effects depending on the type of tissue in which it is expressed.This action may be due to the presence of different subtypes of intracellular receptors or

A)coactivators.
B)cell surface receptors.
C)protein response factors.
D)G protein activity.