Deck 6: Cell Communication

Question 1

How is paracrine signaling different from other types of signaling?

A) The signaling molecule are hormones.
B) The signaling molecules release neurotransmitters.
C) The signaling molecules are displayed on the cell surface.
D) The signaling molecules are transferred by electrical signals.
E) The signaling molecule diffused through interstitial fluid, acting on nearby cells.

Answer 1

E

Question 2

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

A) It function is as an enzyme.
B) It attaches the receptor to the DNA.
C) It holds the receptor within the membrane.
D) It transmits the signal to the inside of the cell.
E) It is the docking site for a signaling molecule.

Answer 2

E

Question 3

During enzyme-linked reception, signal molecules bind to two tyrosine kinase receptors. The receptor proteins move closer together in the plasma membrane and pair, forming a(n) ____.

A) gate
B) dimer
C) pathway
D) polypeptide chain
E) protein kinase cascade

Answer 3

B

Question 4

Which neurotransmitter opens ligand-gated sodium channels?

A) GABA
B) cortisol
C) ecdysone
D) acetylcholine
E) brassinosteroid

Question 5

The outer part of a G protein receptor binds to a(n) ____, and its inner part binds to a(n) ____.

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

Question 6

How are hormones produced by endocrine glands typically transported to target cells?

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

Question 7

Most intracellular receptors are what type of protein?

A) DNA
B) steroids
C) enzymes
D) neurotransmitters
E) transcription factors

Question 8

Which receptor in plant cells is activated by red light?

A) rhodopsin
B) diacylglycerol
C) acetylcholine
D) phytochrome
E) cryptochrome

Question 9

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

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

Question 10

What can happen when GABA binds to its receptor?

A) Neural signaling is inhibited.
B) Sodium ions enter the cell.
C) New signals are transmitted.
D) Muscle contraction is stimulated.
E) Enzyme-linked receptors are activated.

Question 11

Which list describes the correct sequence of events involved in cell signaling?

A) signal transduction, reception, signal transmission, response
B) response, signal transduction, signal transmission, reception
C) signal transmission, signal transduction, reception, response
D) reception, signal transmission, response, signal transduction
E) signal transmission, reception, signal transduction, response

Question 12

What type of cells must receive, relay, and respond to the information signaled?

A) GABA
B) integrins
C) target cells
D) local regulators
E) neurotransmitters

Question 13

Suppose that acetylcholine binds its receptor on the surface of a muscle cell. What happens next?

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

Question 14

Which statement about receptors is false ?

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

Question 15

How are brassinosteroids different from animal steroid hormones?

A) BRs regulate only cell division.
B) BRs are enzyme-linked receptors.
C) BRs bind with intracellular receptors.
D) BRs have a histidine kinase that extends into the cell.
E) BRs bind with a protein kinase receptor in the plasma membrane.

Question 16

What type of chemical compound diffuses across synapses?

A) neurons
B) hormones
C) nitric oxide
D) prostaglandins
E) neurotransmitters

Question 17

How many times do G protein-linked receptors loop back and forth through the plasma membrane?

A) once
B) twice
C) three
D) seven
E) eleven

Question 18

What is typically the result of receptor up-regulation?

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

Question 19

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

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

Question 20

Typically, the gate of an ion channel remains closed until a(n) ____ binds to the receptor.

A) ligand
B) enzyme
C) G protein
D) target cell
E) first messenger

Question 21

During signal transduction of a G protein, the first messenger binds to the receptor, and the G protein is activated. What happens next?

A) formation of cAMP
B) cellular response
C) activation of protein kinase
D) activation of adenylyl cyclase
E) phosphorylation of the G protein

Question 22

What enzyme splits a membrane phospholipid into inositol trisphosphate (IP3) and diacylglycerol (DAG)?

A) phospholipase C
B) protein kinase C
C) adenylyl cyclase
D) protein kinase A
E) phosphodiesterase

Question 23

What type of protein can transduce a signal in two directions?

A) integrins
B) G proteins
C) Ras proteins
D) scaffold proteins
E) phosphorylated proteins

Question 24

The hydrolysis of GTP to GDP deactivates the ____.

A) cAMP
B) G protein
C) Ras protein
D) ligand-gated channel
E) protein kinase pathway

Question 25

In the cAMP signal transduction pathway, a protein kinase is activated. What happens next/

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

Question 26

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

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

Question 27

Which is a major group of enzyme-linked receptors?

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

Question 28

During signal transduction involving G protein and cAMP, what do protein kinases add to target proteins?

A) enzyme
B) substrates
C) calmodulin
D) calcium ions
E) phosphate groups

Question 29

Phosphodiesterase catalyzes the conversion of:

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

Question 30

Which statement about 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 31

Phospholipase C catalyzes the reaction in which:

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

Question 32

What is calmodulin?

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

Question 33

What activates protein kinase C?

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

Question 34

Where are calcium ions stored before a signaling pathway releases them into the cytosol?

A) nucleus
B) ribosome
C) lysosome
D) plasma membrane
E) endoplasmic reticulum

Question 35

Scaffold proteins ensure that signals are relayed ____.

A) slowly
B) efficiently
C) inaccurately
D) methodically
E) simultaneously

Question 36

Which is an example of a second messenger?

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

Question 37

Many intracellular receptors are transcription factors; when activated, they activate or repress specific _____ .

A) genes
B) neurons
C) kinases
D) enyzmes
E) ribosomes

Question 38

Adenylyl cyclase catalyzes the reaction in which:

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

Question 39

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 40

Which molecule is a first messenger but not a second messenger?

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

Question 41

Which statement about Ras proteins is false ?

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

Question 42

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 43

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

Question 44

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 divide uncontrollably.
B) The fibroblasts synthesize excess DAG.
C) The fibroblasts synthesize excess G protein.
D) The fibroblasts no longer respond to calmodulin.
E) The fibroblasts no longer synthesize DNA in response to growth factors.

Question 45

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

Question 46

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

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

Question 47

Compare and contrast local regulators, neurotransmitters, and hormones.

Question 48

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

Question 49

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 50

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

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

Question 51

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

Question 52

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

Question 53

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

Question 54

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

Question 55

What is the process in which one activated receptor can give rise to thousands of final products?

A) signal transcription
B) signal transmission
C) signal transduction
D) signal termination
E) signal amplification

Question 56

What happens when Ras proteins become stuck in their "on" state?

A) Cellar responses are slowed.
B) Additional ions are catalyzed.
C) There is unregulated cell division.
D) There is an increase in protein synthesis.
E) Ligand-gated channels close off the membrane.

Question 57

Which MAP kinase was found to be a signaling molecule for oocyte maturation in mice?

A) Mek and Raf
B) Ras 1 and ERK 2
C) Raf 1 and Raf 2
D) Mek and ERK2
E) ERK 1 and ERK 2

Question 58

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

Question 59

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

Question 60

Which MAP protein kinase is the last to be activated in the MAP kinase pathway?

A) Ras
B) Raf
C) ERK
D) Mek
E) tyrosine

Question 62

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 63

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

Question 64

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

Question 65

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

Question 66

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

Question 67

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 68

What is meant by signal amplification? Provide two examples.

Question 69

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