Deck 6: Cell Communication

Question 1

Hormones produced by endocrine glands are typically transported to target cells:

A) across a synapse.
B) in the blood.
C) in interstitial fluid.
D) via direct contact.
E) through the air.

Answer 1

B

Question 2

Which of the following is NOT an example of an enzyme-linked receptor?

A) a tyrosine kinase
B) the brassinolide receptor
C) the GABA receptor
D) the ethylene receptor
E) a histidine kinase

Answer 2

C

Question 3

An example of a neurotransmitter that opens ligand-gated sodium channels is:

A) GABA.
B) acetylcholine.
C) ecdysone.
D) NO.
E) cortisol.

Answer 3

B

Question 4

In contrast to a G protein-linked receptor and an enzyme-linked receptor, a channel-linked receptor:

A) is located on the cell surface.
B) is composed of seven alpha helices.
C) couples signaling molecules to signal transduction pathways.
D) is a ligand-gated channel.
E) functions as a tyrosine kinase.

Question 5

Which of the following lists the correct sequence of events involved in cell signaling?

A) amplifying, signal transducing, receiving, responding
B) signal transducing, sending, receiving, terminating
C) sending, signal transducing, receiving, amplifying
D) receiving, sending, signal transducing, responding
E) sending, receiving, signal transducing, responding

Question 6

The outer part of a G protein receptor binds __________, and its inner part binds __________.

A) the signaling molecule; tyrosine kinase
B) the signaling molecule; a G protein
C) G protein; tyrosine kinase
D) G protein; an ion channel
E) an ion channel; a G protein

Question 7

Which of the following statements concerning receptors is FALSE?

A) They are found inside the cell and on the cell surface.
B) They are proteins or glycoproteins.
C) They are also called ligands.
D) They are highly selective.
E) They are activated by binding to a signaling molecule.

Question 8

When acetylcholine binds its receptor on the surface of a muscle cell, which of the following happens next?

A) G protein is activated.
B) Tyrosine kinase is activated.
C) Tyrosine is phosphorylated.
D) A neurotransmitter crosses the synapse.
E) A sodium gate opens.

Question 9

Quorum sensing would most likely occur when:

A) Dictyostelium senses cyclic AMP.
B) tobacco plants are attacked by insects.
C) bacteria reach a certain critical concentration.
D) predator insects eat herbivorous insects.
E) insulin binds to target cells.

Question 10

As a result of receptor up-regulation:

A) the number of genes that code for a receptor increases.
B) the sensitivity of a cell to a hormone decreases.
C) the number of receptors decreases.
D) the concentration of hormone molecules in the blood increases.
E) a hormone's signal is amplified.

Question 11

A receptor in plant cells that responds to red light is:

A) brassinolide.
B) diacylglycerol.
C) rhodopsin.
D) cryptochrome.
E) phytochrome.

Question 12

An example of a signaling molecule that binds with a receptor on the cell surface is:

A) insulin.
B) ecdysone.
C) Vitamin D.
D) Vitamin A.
E) nitric oxide.

Question 13

Which of the following is released by cells lining blood vessels and causes a decrease in blood pressure?

A) histamine
B) acetylcholine
C) cyclic AMP
D) nitric oxide
E) prostaglandin

Question 14

Which of the following statements concerning intracellular receptors is FALSE?

A) Their ligands are hydrophobic.
B) Most are transcription factors.
C) Some are located in the cytosol.
D) After binding their ligand, they move out of the cell.
E) Some are bound to DNA.

Question 15

Which of the following would most likely diffuse across a synapse?

A) insulin
B) NO
C) histamine
D) acetylcholine
E) prostaglandins

Question 16

Which of the following is stored in cells of the immune system and released during an allergic reaction?

A) nitric oxide
B) a growth factor
C) histamine
D) a prostaglandin
E) a neurotransmitter

Question 17

Under which of the following situations would receptor down-regulation most likely occur?

A) The concentration of a neurotransmitter is too low.
B) The concentration of a hormone is too high.
C) The number of receptors in the plasma membrane is too low.
D) The number of G proteins is too high.
E) The cell is unable to manufacture cyclic AMP.

Question 18

Paracrine signaling is different from other types of signaling in that the signaling molecule:

A) is produced by endocrine glands.
B) binds to a receptor.
C) is secreted by neurons.
D) is transported in the blood.
E) acts on nearby cells.

Question 19

One difference between the ion channel-linked receptors for GABA and acetylcholine is that when GABA binds its receptor:

A) muscle contraction is inhibited.
B) sodium ions enter the cell.
C) muscle contraction is stimulated.
D) neural signaling is inhibited.
E) chloride ions rush out of the neuron.

Question 20

A receptor on the cell surface usually has several domains.The function of the external domain is:

A) transmitting the signal to the inside of the cell.
B) holding the receptor within the membrane.
C) attaching the receptor to the DNA.
D) functioning as an enzyme.
E) binding the signaling molecule.

Question 21

Adenylyl cyclase is activated directly by:

A) a G protein subunit bound to GTP.
B) a G protein subunit bound to GDP.
C) cAMP.
D) a protein kinase.
E) a hormone.

Question 22

What activates protein kinase C?

A) IP₃
B) DAG
C) cAMP
D) PIP₂
E) calcium ions

Question 23

In the cAMP signal transduction pathway, once a protein kinase is activated, which of the following happens next?

A) G protein is activated.
B) Adenylyl cyclase is activated.
C) GDP is replaced by GTP.
D) cAMP is converted to ATP.
E) The protein kinase activates a cellular response.

Question 24

Calmodulin is a:

A) hormone.
B) calcium-binding protein.
C) phosphatase.
D) protein kinase.
E) phospholipase.

Question 25

In the signal transduction pathway involving cAMP, once cAMP is formed, it then activates:

A) protein kinase A.
B) adenylyl cyclase.
C) G protein.
D) protein kinase C.
E) IP₃.

Question 26

The main signaling cascade for cell division and differentiation is the __________ cascade.

A) phospholipase C
B) MAP kinase
C) phosphoinositol
D) cAMP
E) calcium-calmodulin

Question 27

When a receptor binds to its G protein, which of the following happens next?

A) The signaling molecule binds to the receptor.
B) The G protein activates an enzyme.
C) The three G protein subunits come together.
D) GTP is replaced by GDP.
E) GDP is replaced by GTP.

Question 28

Which of the following statements concerning Ras proteins is FALSE?

A) They are inactivated when phosphorylated.
B) They are G proteins.
C) They are active when bound to GTP.
D) They are activated by tyrosine kinase receptors.
E) They include MAP kinases.

Question 29

Which of the following statements concerning calmodulin is FALSE?

A) It activates protein kinases.
B) It activates phosphatases.
C) It is a protein.
D) It is found in all eukaryotic cells studied.
E) It binds a maximum of three calcium ions.

Question 30

A protein kinase catalyzes the reaction in which:

A) a protein loses a phosphate group.
B) a protein is phosphorylated.
C) G protein is activated.
D) ATP is converted to cAMP.
E) GTP is converted to GDP.

Question 31

Phospholipase C catalyzes the reaction in which:

A) IP₃ is converted to DAG.
B) PIP₂ is split.
C) a protein kinase is activated.
D) calcium ions are released from the ER.
E) DAG is converted to PIP₂.

Question 32

Adenylyl cyclase catalyzes the reaction in which:

A) a protein is phosphorylated.
B) ATP is converted to cAMP.
C) GTP is converted to GDP.
D) PIP₂ is split.
E) calcium ions bind calmodulin.

Question 33

In the IP₃ pathway, what is the function of IP₃?

A) activate protein kinase C
B) activate phospholipase C
C) phosphorylate a protein
D) bind calcium channels in the ER
E) activate adenylyl cyclase

Question 34

A molecule that is a first messenger but not a second messenger is:

A) cyclic AMP.
B) G protein.
C) adenylyl cyclase.
D) protein kinase.
E) acetylcholine.

Question 35

Which of the following statements concerning G protein is FALSE?

A) Its subunits can separate.
B) One subunit is a GTPase.
C) One subunit binds GTP.
D) One subunit binds GDP.
E) One subunit binds ATP.

Question 36

You conduct an experiment in which you inactivate Ras proteins in fibroblast cells.Which of the following is the most immediate consequence of this procedure?

A) The fibroblasts synthesized excess G protein.
B) The fibroblasts synthesized excess DAG.
C) The fibroblasts no longer responded to calmodulin.
D) The fibroblases no longer synthesized DNA in response to growth factors.
E) The fibroblasts divided uncontrollably.

Question 37

In the phospholipase C signal transduction pathway, which are second messengers?

A) phospholipase C and G protein
B) PIP₂ and IP₃
C) cAMP and IP₃
D) phospholipase C and protein kinase A
E) IP₃ and DAG

Question 38

A major group of enzyme-linked receptors are:

A) phospholipases.
B) adenylyl cyclases.
C) tyrosine kinases.
D) G proteins.
E) ion channels.

Question 39

An example of a second messenger is:

A) protein kinase A.
B) an ion channel.
C) cyclic AMP.
D) GABA.
E) insulin.

Question 40

Which of the following statements concerning calcium ions is FALSE?

A) They are involved in fertilization, blood clotting, and microtubule disassembly.
B) Their concentration in the cytosol rises when Ca²⁺ gates open in the ER.
C) Their concentration in the cytosol is usually higher than in the extracellular fluid.
D) They can act by themselves, without binding to calmodulin.
E) They can exert an effect after binding to calmodulin.

Question 41

When signal molecules bind to two tyrosine kinase receptors, the receptors move closer to each other and form a monomer.
__________________

Question 42

Compare and contrast local regulators, neurotransmitters, and hormones.

Question 43

Which of the following statements concerning intracellular receptors is FALSE?

A) Some bind hydrophobic signaling molecules.
B) Some function as transcription factors.
C) They diffuse across the plasma membrane of target cells.
D) The ligand-receptor complex can activate genes.
E) The ligand-receptor complex can inactivate genes.

Question 44

In what part of the cell does a polar signaling molecule bind its receptor? A nonpolar signaling molecule? Explain your reasoning.

Question 45

The function of scaffolding proteins is to:

A) phosphorylate proteins in a cascade.
B) dephosphorylate proteins in a cascade.
C) convert ATP and GTP to cAMP and cGMP, respectively.
D) regulate the MAP kinase pathway.
E) stimulate the release of calcium ions from the ER.

Question 46

When an enzyme linked receptor is activated, a conformational change activates the extracellular kinases.
__________________

Question 47

Why is it important for cells to be able to communicate with one another? List the main steps involved in cell signaling.

Question 48

What is calmodulin, and what role does it play in signal transduction?

Question 49

Insulin stimulates cells to take in glucose by facillitated diffusion, so insulin receptor-down regulation increases the ability of cells to take in glucose.
__________________

Question 50

Choanoflagellates have been important for the study of cell communication evolution because choanoflagellates have:

A) signal transduction pathways unlike those in other bacteria.
B) signaling molecules similar to those of other protists.
C) signal transduction pathways that interfere with the cells they infect.
D) protein kinases similar to those in animals.
E) G proteins different from those in prokaryotes.

Question 51

The cholera toxin causes a(n) __________ of chloride channels in cells of the intestine and the resulting __________.

A) closing; loss of blood
B) closing; movement of neutrophils toward the bacterium
C) opening; assembly of microtubules
D) opening; gain of water
E) opening; loss of water

Question 52

Which of the following responses involves the activation of ion channels?

A) Ras pathway activation of microfilament assembly in neutrophils
B) steroid hormone regulation of gene expression
C) Ras pathway activation of genes for cell division
D) peptide-stimulated assembly of microtubule assembly in neutrophils
E) serotonin-stimulated transmission of a neural impulse

Question 53

When a signaling molecule binds to a G protein linked receptor, the ligand-receptor complex associates with GDP protein and causes GDP to be replaced by GTP.
__________________

Question 54

Integrins are unusual in that they:

A) are steroids.
B) are specific transmembrane proteins.
C) respond to information received from inside and outside the cell.
D) stimulate both the Ras pathway as well as the IP₃ pathway.
E) are found only in Arabidopsis thaliana.

Question 55

Phosphodiesterase catalyzes the conversion of:

A) a protein to a phosphorylated protein.
B) GDP to GTP.
C) cAMP to AMP.
D) IP₃ to PIP₂.
E) calcium to calcium-calmodulin.

Question 56

What is the difference between a first messenger and a second messenger? Give an example of each.

Question 57

The outer part of the enzyme linked receptor has a binding site for a signaling molecule, and the part of the receptor that extends into the cytosol has a binding site for a specific G protein.
__________________

Question 58

All of the following are examples of signal termination EXCEPT:

A) one cAMP molecule activating many protein kinases.
B) phosphodiesterase converting cGMP to GTP.
C) GTPase converting GTP to GDP.
D) the inactivation of G protein by the cholera toxin.
E) phosphatase removing the phosphate group from a protein.

Question 59

Ion channels are found in the plasma membranes of neurons and muscle cells.
__________________

Question 60

When food is abundant , the cellular slime mold secretes cAMP into the environment to signal the formation of a multicellular slug-shaped colony.
__________________

Question 61

What is meant by signal amplification? Give two examples.

Question 62

MATCHING
Match receptor with activated state.Answers should be used more than once.
a.Ion channel linked receptor
c.Enzyme linked receptor
b.G protein linked receptor
DAG is the second messenger.

Question 63

MATCHING
Match receptor with activated state.Answers should be used more than once.
a.Ion channel linked receptor
c.Enzyme linked receptor
b.G protein linked receptor
Protein kinase sites are active.

Question 64

Injecting fibroblasts with anti-Ras antibodies that inactivate Ras proteins increases cell division response to growth factors.
__________________

Question 65

Compare and contrast the signal transduction pathway involving cAMP with that involving phospholipids.

Question 66

Barbituates and benzodiazpine drugs bind to GABA receptors to open chloride channels, inhibit neural impulse, and induce tranquility.
__________________

Question 67

MATCHING
Match receptor with activated state.Answers should be used more than once.
a.Ion channel linked receptor
c.Enzyme linked receptor
b.G protein linked receptor
Phosphate comes from ATP.

Question 68

MATCHING
Match receptor with activated state.Answers should be used more than once.
a.Ion channel linked receptor
c.Enzyme linked receptor
b.G protein linked receptor
GDP is replaced with GTP.

Question 69

Scaffold proteins organize groups of intracellular signaling kinases into signaling complexes.
__________________

Question 70

MATCHING
Match receptor with activated state.Answers should be used more than once.
a.Ion channel linked receptor
c.Enzyme linked receptor
b.G protein linked receptor
Sodium ions enter the cell.

Question 71

Compare and contrast the structure and function of ion channel-linked receptors, G protein-linked receptors, and enzyme-linked receptors.In general, how do they differ from intracellular receptors?

Question 72

MATCHING
Match receptor with activated state.Answers should be used more than once.
a.Ion channel linked receptor
c.Enzyme linked receptor
b.G protein linked receptor
Explain the differences between receptor up-regulation and down-regulation including the conditions under which a cell would use one rather than the other.

Question 73

Give some examples showing how cells respond to signals.How are signals terminated?