Deck 7: Cell Signaling and Communication

Question 1

Which of the following is not a common type of receptor?

A) Ion channel
B) Protein kinase
C) G protein-linked receptor
D) Cytoplasmic receptor
E) Adenylyl cyclase

Answer 1

E

Question 2

Which of the following statements about cell signaling in voles is false?

A) A signal transduction pathway can bring about changes in behavior.
B) Oxytocin and vasopressin are signals that induce bonding and caring behaviors in voles.
C) Oxytocin acts as a signal for premating behaviors.
D) The interaction of the receptor and the signal causes the receptor to change shape.
E) Although oxytocin and vasopressin are widely circulated in the bloodstream, they only bind to a few cell types.

Answer 2

C

Question 3

Plasmodesmata and gap junctions

A) allow small molecules and ions to pass rapidly between cells.
B) are both membrane-lined channels.
C) are channels about 1 mm in diameter.
D) are present only once per cell.
E) are involved in cell recognition.

Answer 3

A

Question 4

Which of the following is not a consequence of a signal binding to a receptor?

A) Activation of receptor enzyme activity
B) Diffusion of the receptor in the plasma membrane
C) Change in conformation of the receptor protein
D) Breakdown of the receptor to amino acids
E) Release of the signal from the receptor

Question 5

Signals reach target cells in multicellular organisms via _______ and _______.

A) circulation; diffusion
B) conduction; diffusion
C) circulation; perspiration
D) chaperon trafficking; transmembrane transport
E) cytoskeletal trafficking; perfusion

Question 6

The signals that bind to receptors on nearby cells are known as

A) paracrine signals.
B) parasitic signals.
C) autocrine signals.
D) hormones.
E) responders.

Question 7

What is the correct order for the following events in the interaction of a cell with a signal? (1) Alteration of cell function; (2) signal binds to receptor; (3) signal released from source; (4) signal transduction.

A) 1234
B) 2314
C) 3214
D) 3241
E) 3421

Question 8

The first component of a signal transduction pathway is a(n)

A) paracrine molecule.
B) responder.
C) receptor.
D) hormone.
E) effector molecule.

Question 9

The major difference between a cell that responds to a signal and one that does not is the presence of a

A) DNA sequence that binds to the signal.
B) nearby blood vessel.
C) receptor.
D) second messenger.
E) transduction pathway.

Question 10

Steroid hormones such as estrogen act on target cells by

A) initiating second messenger activity.
B) binding to membrane proteins.
C) initiating gene expression.
D) activating enzymes.
E) binding to membrane lipids.

Question 11

Which of the following is not a second messenger?

A) Calcium ion
B) Inositol trisphosphate
C) ATP
D) Cyclic AMP
E) Diacylglycerol

Question 12

Cells receive which of the following signals?

A) Light
B) Sound
C) Odorants
D) Hormones
E) All of the above

Question 13

Which of the following statements is false?

A) Plants respond to light as a signal.
B) The environment experienced by a cell deep inside a large multicellular organism is very different from the external environment.
C) Some plants are capable of responding to temperature fluctuations.
D) Some cells can self-stimulate cell division by making their own division signals.
E) None of the above

Question 14

Which of the following is not true of a protein kinase cascade?

A) The signal is amplified.
B) A second messenger is formed.
C) Target proteins are phosphorylated.
D) The cascade ends up at the mitochondrion.
E) The cascade begins at the plasma membrane.

Question 15

A nonpolar molecule such as a steroid hormone usually binds to a

A) cytoplasmic receptor.
B) protein kinase.
C) ion channel.
D) phospholipid.
E) second messenger.

Question 16

Why do some signals ("first messengers") trigger "second messengers" to activate target cells?

A) The first messenger requires activation by ATP.
B) The first messenger is not water soluble.
C) The first messenger binds to many types of cells.
D) The first messenger cannot cross the plasma membrane.
E) There are no receptors for the first messenger.

Question 17

The signals that bind to receptors of the same cell that made them are known as

A) paracrine signals.
B) parasitic signals.
C) autocrine signals.
D) hormones.
E) responders.

Question 18

Which of the following statements is true?

A) Eukaryotic, but not prokaryotic, cells process information from their environment.
B) Prokaryotic, but not eukaryotic, cells process information from their environment.
C) The mere presence of a signal will cause a cell to respond to it.
D) Light can be a signal.
E) Sense organs allow cells to respond to physical signals but not chemical signals.

Question 19

Most of the chemical signals coming to a cell deep inside a multicellular organism come from

A) the external environment.
B) the lymphatic system.
C) other cells.
D) the nervous system.
E) None of the above

Question 20

To respond to a signal, a cell must have a(n) _______ molecule that can detect the signal.

A) paracrine
B) receptor
C) autocrine
D) responder
E) All of the above

Question 21

The receptor of estrogen

A) is an ion channel receptor.
B) is a protein kinase receptor.
C) exists within the plasma membrane.
D) exists within the cytoplasm.
E) None of the above

Question 22

Which of the following is true?

A) For most ligand-receptor complexes, binding is favored.
B) Ligand-receptor interactions are reversible.
C) Many drugs that alter human behavior prevent binding of receptors' specific ligands.
D) Both a and b
E) All of the above

Question 23

Which of the following is most likely to involve the circulatory system?

A) Paracrine signals
B) Parasitic signals
C) Autocrine signals
D) Hormones
E) Responders

Question 24

In the E. coli signal transduction pathway, changes in the aqueous media cause part of the receptor to undergo a change in

A) responder.
B) conformation.
C) hormonal activity.
D) amplification.
E) extracellular environment.

Question 25

In the E. coli signaling transduction pathway, which of the following is true about the OmpR protein?

A) When phosphorylated, it acts as a transcription factor for OmpC.
B) It exists both inside and outside the cell membrane.
C) It is a receptor.
D) Both a and b
E) All of the above

Question 26

The second component of a signal transduction pathway is known as a

A) receptor.
B) hormone.
C) responder.
D) transducer.
E) None of the above

Question 27

The conformational change in EnvZ causes it to become a(n)

A) autocrine receptor.
B) responder.
C) ligand.
D) protein kinase.
E) phosphate group.

Question 28

In general, all cell signaling causes

A) increased expression of genes.
B) an influx of ions.
C) protein kinase activity.
D) G protein activation.
E) a change in receptor conformation.

Question 29

The transmembrane protein EnvZ in a signal transduction pathway found in E. coli is an example of a(n)

A) autocrine molecule.
B) transductor.
C) responder.
D) hormone.
E) None of the above

Question 30

In the E. coli signal transduction pathway, which of the following protein molecules acts as the responder?

A) OmpR
B) EnvZ
C) SORp
D) Autocrine
E) None of the above

Question 31

Caffeine mimics the molecular structure of

A) paracrine.
B) aspirin.
C) adenosine.
D) autocrine.
E) None of the above

Question 32

The phosphorylation and change in shape of the responder in the E. coli signaling transduction pathway is a key event in signaling for which of the following reasons?

A) The signal that originally was on the outside of the cell has been transduced to a protein that exists totally within the cell's cytoplasm.
B) The signal has been amplified.
C) The altered responder can bind to DNA and stimulate transcription of one or more genes.
D) Both a and c
E) All of the above

Question 33

Which of the following is false?

A) Cells are bombarded with numerous signals, but they respond to only a few.
B) A cell's receptors determine whether or not the cell will respond to a signal.
C) Receptor proteins are very specific.
D) There are only a few kinds of signal receptor proteins.
E) None of the above

Question 34

In order, from start to finish, the basic steps of a signal transduction pathway are

A) signal, responder, receptor, effects.
B) receptor, signal, responder, effects.
C) signal, receptor, responder, effects.
D) signal, receiver, responder, effects.
E) None of the above

Question 35

Signals that travel to distant cells through the circulatory system are known as

A) paracrine signals.
B) parasitic signals.
C) autocrine signals.
D) hormones.
E) responders.

Question 36

In what way do ligand-receptor interactions differ from enzyme-substrate reactions?

A) The ligand signal is not usually metabolized into useful products.
B) Receptor-ligand interactions do not obey the laws of mass action.
C) Inhibitors never bind to the ligand-binding site.
D) Reversibility never occurs in the ligand-receptor interaction.
E) The enzyme-substrate reaction and the ligand-receptor interaction do not differ.

Question 37

Signal molecules can be divided into two general classes according to their receptors. What are these two kinds of receptors?

A) Plasma membrane and ion channel
B) Plasma membrane and protein kinase
C) Ion channel and protein kinase
D) G protein-linked and protein kinase
E) None of the above

Question 38

A molecule that binds to the particular three-dimensional structure of another molecule's receptor site is known as a(n)

A) responder.
B) receptor.
C) ligand.
D) ion channel.
E) filament.

Question 39

Which of the following is true about EnvZ?

A) It phosphorylates itself during signal transduction.
B) It has domains on both the inside and the outside of the cell.
C) It acts as a responder.
D) Both a and b
E) All of the above

Question 40

In the E. coli signaling transduction pathway, which of the following is true about OmpC?

A) It is a transcription factor.
B) It can insert itself into the outer membrane, resulting in the eventual restoration of homeostasis.
C) It phosphorylates other proteins.
D) It is a receptor.
E) None of the above

Question 41

Second messengers

A) are typically very specific in their activity.
B) do not amplify a signal.
C) have enzymatic activity.
D) can be derived from lipids.
E) All of the above

Question 42

Which molecule acts as a second messenger in the cascade by which epinephrine stimulates the activation of the enzyme glycogen phosphorylase?

A) Adenosine
B) Caffeine
C) Citric acid
D) Cyclic AMP
E) Adenylyl cyclase

Question 43

During what part of the signal transduction pathway is Ras activated?

A) Early in the pathway
B) Around the midpoint
C) Late in the pathway
D) All along the pathway
E) None of the above

Question 44

Which of the following is true about the abnormal form of Ras found in bladder cancer cells?

A) Because it is inactive, it is unable to inhibit growth factors.
B) It is always active because it is continuously bound to GTP.
C) If it were inhibited, cells would continue to divide.
D) It acts as an ion channel receptor.
E) It stimulates epinephrine.

Question 45

How does a protein kinase cascade amplify an intercellular signal?

A) Protein kinase opens cell junctions, amplifying the intercellular signal.
B) The activated G protein binds and activates a second protein, amplifying the signal.
C) Nitric oxide opens cell channels, which allows protein kinase molecules to move quickly from cell to cell.
D) Second messengers create shortcuts that create multiple cascades.
E) One activated receptor kinase molecule can trigger the activation of thousands of proteins.

Question 46

Which of the following is true?

A) Direct transduction is more common than indirect transduction.
B) In indirect transduction, second messengers mediate the interaction between the receptor and the cell's response.
C) Amplification never occurs via second messengers.
D) Indirect transduction occurs at the plasma membrane.
E) All of the above

Question 47

Vitamin A is a relatively small, lipid-soluble molecule that can behave as a hormone. Its receptor

A) is an ion channel receptor.
B) is a protein kinase receptor.
C) involves a G protein.
D) is not connected to the plasma membrane.
E) does not exist; vitamin A does not have a receptor.

Question 48

Which of the following statements is true?

A) G proteins contain only one important binding site.
B) When a G protein binds to an activated receptor protein, ADP is exchanged for ATP.
C) G protein receptors are single proteins that have seven distinct regions that pass through the phospholipid bilayer of the cell membrane.
D) G proteins can only activate effector proteins; they cannot inhibit them.
E) None of the above

Question 49

Which of the following strongly binds to the acetylcholine receptor?

A) Estrogen
B) Acetylcholine
C) Sodium
D) OmpC
E) Protein kinases

Question 50

A benefit of the many steps involved in protein kinase cascades is that they allow for

A) some specificity of the response.
B) amplification of the signal.
C) information to be communicated to the nucleus.
D) variation in the response.
E) All of the above

Question 51

Which of the following molecules has an ion channel receptor?

A) Insulin
B) Estrogen
C) Acetylcholine
D) Lithium
E) None of the above

Question 52

For a G protein to play its part in moving events forward in a signal pathway,

A) GDP must be released, and a GTP must occupy the nucleotide-binding site.
B) GTP must be released, and a GDP must occupy the nucleotide-binding site.
C) cGMP must occupy the otherwise empty nucleotide-binding site.
D) cGMP must leave the otherwise occupied nucleotide-binding site.
E) None of the above

Question 53

Which of the following statements about the insulin receptor is false?

A) It autophosphorylates.
B) It requires binding by two insulin molecules to be activated.
C) It catalyzes the phosphorylation of insulin response substrates.
D) It is located entirely within the cytoplasm.
E) None of the above

Question 54

If a G protein were unable to release its bound nucleo­tide but could hydrolyze it, signal transduction would

A) cease.
B) be continuous.
C) be unaffected.
D) be constantly switching on and off.
E) be unpredictable.

Question 55

After the GTP-bound subunit of the G protein separates from the rest of the G protein, it travels until it encounters

A) an activator.
B) a receptor.
C) an effector protein.
D) a protein kinase.
E) another G protein.

Question 56

Which of the following is true about acetylcholine?

A) It binds to a sodium channel receptor.
B) It acts as a neurotransmitter.
C) The binding of two molecules of acetylcholine to a receptor are required to open the channel.
D) It moves against the concentration gradient.
E) All of the above

Question 57

Which of the following would likely not be observed in a person injected with epinephrine?

A) Contraction of muscles surrounding the blood vessels that line the digestive tract
B) Increased activity of heart muscle
C) Increased glucose mobilization
D) Activation of G proteins
E) All of the above would occur.

Question 58

Which of the following molecules has a protein kinase receptor?

A) Insulin
B) Estrogen
C) Acetylcholine
D) Sodium
E) G proteins

Question 59

If a G protein were able to release its bound nucleotide but not to hydrolyze it, signal transduction would

A) cease.
B) be continuous.
C) be unaffected.
D) be constantly switching on and off.
E) be unpredictable.

Question 60

What is the G protein that has been found in many human bladder cancers?

A) Acetylcholine
B) Rap
C) Ras
D) Rats
E) None of the above

Question 61

Which of the following statements is true?

A) Some mammals have over 1,000 genes for odor signal receptors.
B) The signal transduction pathway triggered by odorant molecules results in the opening of ion channels.
C) Each of the thousands of neurons in the nose expresses one of the odor signal receptors.
D) Odorant receptors are G protein-linked.
E) All of the above

Question 62

Which of the following about nitric oxide is true?

A) Because it is chemically stable, it is able to travel relatively long distances.
B) It does not diffuse readily.
C) It is released by nitroglycerin, resulting in the relaxation of blood vessels.
D) Calcium ions inhibit the enzyme that catalyzes nitric oxide.
E) All of the above

Question 63

Which of the following statements is false?

A) Calcium ions can stimulate their own release from intracellular stores.
B) The opening of calcium channels takes place relatively slowly, from seconds to minutes.
C) Calcium ions can act as second messengers.
D) The entry of a sperm into an egg causes a massive opening of calcium channels.
E) Increases in calcium can result in the activation of protein kinase C.

Question 64

Lithium can be effective in the treatment of bipolar disorder because it

A) opens up the lithium ion channel.
B) acts as a second messenger accelerating the IP₃/DAG signal transduction pathway.
C) inhibits G protein activation of phospholipase C and inhibits synthesis of IP₃.
D) changes the osmotic balance of cells.
E) acts as a neurotransmitter.

Question 65

Increased synthesis of phosphodiesterase would lead to

A) decreased concentration of cyclic AMP.
B) increased concentration of cyclic AMP.
C) increased concentration of calmodium.
D) decreased concentration of calmodium.
E) inhibition of adenylyl cyclase.

Question 66

Gap junctions transverse the gap between plasma membranes of two cells by means of

A) plasmodesmata.
B) desmosomes.
C) connexons.
D) cyclic AMP.
E) direct transduction.

Question 67

Which of the following is not involved in the signaling cascade after the odorant molecule binds to its receptor?

A) Activation of a G protein
B) Cyclic AMP used as a second messenger
C) Nitric oxide used as second messenger
D) Gated opening of ion channels
E) All of the above are involved in the signaling cascade.

Question 68

Which of the following are specialized cell junctions that allow neighboring cells to communicate directly?

A) Tight junctions
B) Gap junctions
C) Desmosomes
D) Ion channels
E) G proteins

Question 69

Viagra, used to treat erectile dysfunction, acts by means of the release of the second messenger

A) cyclic AMP.
B) calcium ion.
C) nitric oxide.
D) calmodulin.
E) acetylcholine.

Question 70

Which of the following represents the correct ordering of the molecules that are activated by a single molecule of epinephrine, from highest number of molecules to lowest number of molecules?

A) cAMP, protein kinase A, phosphorylase kinase, glycogen phosphorylase
B) Glycogen phosphorylase, phosphorylase kinase, protein kinase A, cAMP
C) cAMP, phosphorylase kinase, glycogen phosphorylase, protein kinase A
D) Glycogen phosphorylase, cAMP, protein kinase A, phosphorylase kinase
E) Phosphorylase kinase, glycogen phosphorylase, cAMP, protein kinase A

Question 71

In gap junctions, the channel pores permit the transport of

A) small signal molecules.
B) ions.
C) proteins.
D) Both a and b
E) All of the above

Question 72

Which of the following statements about gap junctions is true?

A) They generally occupy less than 5 percent of the area of the plasma membrane.
B) They are specialized structures that permit metabolic cooperation among the linked cells.
C) They occur only in plants.
D) They are made of G proteins.
E) All of the above

Question 73

Which of the following statements about cyclic AMP is false?

A) It can bind to, and thus open, ion channels in some sensory cells.
B) In some circumstances it can bind to a protein kinase in the cytoplasm.
C) The enzyme adenylyl cyclase catalyzes its formation from ATP.
D) It is a second messenger.
E) It has enzymatic activity.

Question 74

Which of the following statements is false?

A) Diacylglycerol can act as a second messenger.
B) Inositol triphosphate can act as a second messenger.
C) Protein kinase C can phosphorylate a wide variety of proteins.
D) Inositol triphosphate remains bound to the membrane after phospholipase C catalyzes its formation.
E) Inositol triphosphate can open an ion channel, releasing calcium into the cytoplasm.

Question 75

IP₃ is released into the cytoplasm when PIP2 is hydrolyzed. IP₃

A) opens Ca²⁺ channels.
B) closes Ca²⁺ channels.
C) stimulates G protein activation of phospholipase C.
D) activates cyclic AMP.
E) produces calcium-binding protein S4.

Question 76

Which of the following statements is true?

A) Most cells are in contact with their neighbors.
B) Tight junctions are specialized for intercellular communication.
C) Desmosomes are specialized for intercellular communication.
D) Gap junctions are channels between adjacent cells.
E) All of the above

Question 77

Which of the following statements about calcium is true?

A) Calcium ions are more concentrated inside than outside the cell.
B) Active transport maintains the concentration difference of calcium ions.
C) A cell can increase intracellular concentrations of calcium by making more calcium.
D) IP₃ is the only signal that causes calcium channels to open.
E) It inhibits cell division in fertilized eggs.

Question 78

The concentration of cAMP in a cell is increased by

A) phosphodiesterase.
B) cGMP.
C) a protein kinase.
D) a second messenger.
E) a G protein.

Question 79

The G protein-mediated cascade stimulated by epine­phrine results in the phosphorylation of two key enzymes. The eventual results of this phosphorylation are the _______ of glycogen synthase and the _______ of glycogen phosphorylase.

A) stimulation; stimulation
B) stimulation; inhibition
C) inhibition; stimulation
D) inhibition; inhibition
E) inhibition; introversion

Question 80

The hydrolysis of PIP2 results in

A) inositol triphosphate and diacylglycerol.
B) inositol triphosphate and cyclic AMP.
C) two second messengers.
D) Both a and c
E) Both b and c