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CHAPTER 7—CELL COMMUNICATION
MULTIPLE CHOICE
1. In order for a cell to receive a signal, it must possess an appropriate ____.
a.
glycolipid
b.
glycoprotein
c.
receptor
d.
transfer protein
e.
hormone
2. When a cell binds a signal molecule, it may affect ____.
a.
gene activity
b.
protein synthesis
c.
cell division
d.
secretion
e.
all of these
3. Cells CANNOT communicate with each other by means of _______.
a.
gap junctions.
b.
plasmodesmata
c.
a molecule that diffuses through the extracellular fluid.
d.
desmosomes.
e.
hormones
4. Adjacent animal cells utilize ____ to rapidly communicate with each other.
a.
gap junctions
b.
plasmodesmata
c.
hormones
d.
desmosomes
e.
neurotransmitters
5. Adjacent plant cells utilize ____ to rapidly communicate with each other.
a.
gap junctions
b.
plasmodesmata
c.
transport proteins
d.
desmosomes
e.
neurotransmitters
6. In order for a cell to respond to the signaling molecule epinephrine, it must ____.
a.
have ion channels
b.
have a lipid bilayer that allows the response to occur
c.
have receptors exposed on the inner plasma membrane surface
d.
have receptors exposed on the plasma membrane surface
e.
have nuclear membrane receptors
7. 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 membrane interior
8. Nonpolar signal molecules enter the cell by ____.
a.
facilitated diffusion
b.
simple diffusion
c.
osmosis
d.
active transport
e.
receptor-mediated endocytosis
9. Examples of nonpolar signal molecules include ____.
a.
epinephrine
b.
insulin
c.
estrogen and testosterone
d.
growth factors
e.
neurotransmitters
10. What is the response of a cell surface receptor to the binding of a signal molecule?
a.
The cell surface receptor denatures.
b.
The signal is transduced through the plasma membrane into the cell.
c.
The receptor relays a signal to another location of 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.
11. The overall process in which information carried by a signal molecule is translated into changes that
occur inside the cell is called ____.
a.
signal digestion
b.
signal digression.
c.
signal induction
d.
signal interaction
e.
signal transduction
12. You have recently identified a molecule you believe to be a signal molecule associated with signal
transduction. All you know about this signal molecule is that chemically it is hydrophilic. As a result
you expect it to interact with ____.
a.
a receptor on the cell surface
b.
a receptor within the cytoplasm of the cell
c.
a receptor in the nucleus of the cell
d.
a receptor on the cytoplasmic surface of the plasma membrane
e.
a receptor associated with the endoplasmic reticulum
13. 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 within a cell
d.
by the transport of ions between cells in different parts of the organism
e.
by the transport of ions in water
14. In the 1950s, Earl Sutherland and colleagues discovered that epinephrine ____.
a.
leads to release of a second messenger that ultimately results in hydrolysis of glycogen to
glucose
b.
leads to 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
15. The two major categories of extracellular signal 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
16. In the process of quorum sensing, bacteria release signal molecules in _____ concentration as cell
density _____.
a.
increasing; decreases
d.
decreasing; decreases
b.
increasing; increases
e.
a constant; increases
c.
decreasing; increases
17. A pathway for cell growth control is conserved between Drosophila and humans, indicating that the
pathway is _______.
a.
also found in prokaryotes
d.
at least 3.8 billion years old
b.
also found in all animals
e.
at least 8 million years old
c.
at least 800 million years old
18. Neurotransmitters are molecules released by ____.
a.
gonads
b.
polar hormones
c.
peptide hormones
d.
cells in the blood
e.
neurons
19. The surface receptors that recognize and bind signal molecules are ____.
a.
glycoproteins
b.
glycolipids
c.
phospholipids
d.
promoters
e.
cadherins
20. As you recall, a single enzyme molecule may catalyze a reaction many times. In signal transduction
pathways, which may utilize several enzymes, the result is _________.
a.
amplification of the final product
b.
denaturation of non-essential proteins
c.
hydrolysis of signal molecules
d.
transformational modification of the receptor
e.
change in cell membrane permeability
21. Recognition of a chemical signal by a receptor protein in a membrane is most similar to ____.
a.
mRNA specifying the sequence of amino acids in a specific metabolic pathway operating
in an organelle
b.
binding of a specific substrate to the active site of an enzyme
c.
turning on transcription of a gene
d.
allosteric regulation of proteins
e.
an enzyme requiring a specific optimum pH and temperature for activity
22. In most cases, protein kinases ____.
a.
add phosphate groups to proteins
b.
bind cGMP
c.
stimulate adenylyl cyclase
d.
polymerize amino acids
e.
hydrolyze proteins
23. The effects of protein kinases are reversed by another group of enzymes called ____.
a.
hydrolases
b.
catalases
c.
isomerases
d.
phosphatases
e.
proteases
24. Once transduction of a signal is complete, the receptor and its bound signal molecule are removed
from the cell surface by ____.
a.
hydrolysis
b.
diffusion
c.
endocytosis
d.
pinocytosis
e.
exocytosis
25. The protein kinase activity of the receptor protein-tyrosine kinase is located ____.
a.
on the extracellular surface of the membrane
b.
on the cytoplasmic side of the cell membrane
c.
within the hydrophobic portion of the lipid bilayer
d.
in the nuclear membrane
e.
in the cystol
26. Receptor protein-tyrosine kinases add phosphate groups to which amino acid on the receptor?
a.
serine
b.
glycine
c.
threonine
d.
tryptophan
e.
tyrosine
27. What is the immediate result once a signal molecule binds to a receptor protein-tyrosine kinase?
a.
receptor dimerization
b.
receptor trimerization
c.
receptor denaturation
d.
receptor polymerization
e.
receptor hydrolysis
28. Structurally similar receptor tyrosine kinases have been found in all multicellular animals. This
suggests 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 cannot be involved in processes vital to animals
e.
RTKs have evolved independently of each other in animals
29. The receptors for a group of peptide signaling molecules known as growth factors are typically ____.
a.
receptor tyrosine kinases
b.
cyclic AMP
c.
neurotransmitters
d.
G protein-linked receptors
e.
ligand-gated ion channels
30. Which one of the following would be the most likely result of a peptide growth factor binding to its
receptor?
a.
phosphorylase activity
b.
adenylyl cyclase activity
c.
protein kinase activity
d.
GTPase activity
e.
protein phosphatase activity
31. The toxin of Vibrio cholerae causes severe diarrhea because it ____.
a.
modifies DAG and activates a cascade of protein kinases
b.
activates phospholipase to produce inositol triphosphate
c.
decreases the cytosolic concentration of Ca++
d.
modifies a G protein involved in regulating salt and water secretion
e.
binds with adenylyl cyclase and triggers formation of cAMP
32. Which one of the following is a common second messenger?
a.
cGTP
b.
cMHC
c.
cATP
d.
cAMP
e.
cGDP
33. 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 a cell membrane to the outside of the cell
d.
decrease the message once the signal molecules have left the receptor
e.
relay the message from the inner surface of the plasma membrane throughout the
cytoplasm
34. In the cAMP pathway, the G protein activates ____.
a.
adenylyl cyclase
b.
diacylglycerol (DAG)
c.
phospholipase C
d.
inositol triphosphate
e.
phosphodiesterase
35. Once activated, cAMP is quickly degraded to AMP by ____ which results in switching off the signal
pathway.
a.
adenylyl cyclase
b.
diacylglycerol (DAG)
c.
phospholipase C
d.
acetylcholinesterase
e.
phosphodiesterase
36. Ras proteins are of interest to researchers because ____.
a.
of their role in reproduction
d.
of their role in relieving cluster headaches
b.
of their role in liking plant hormones to
germination
e.
of their role in bringing about the fight –
or-flight response
c.
of their role in the development of many
types of cancer
37. Aequorin, a protein produced by jellyfish and ctenophores, can be used to detect the release of Ca2+ ,
an important control element in many eukaryotic cells, into the cytosol by
a.
releasing a burst of light.
b.
depolarizing the cell membrane.
c.
causing a conformational change in the shape of G proteins.
d.
phosphorylating tyrosine.
e.
More than one answer is correct.
38. The reason that some individual hormones have so many different effects is that
a.
they influence gene transcription.
b.
they trigger a second messenger system that produces a cascade effect.
c.
there are a great many different cells in different tissues that have specific receptors for the
hormone.
d.
the hormone is carried throughout the body and only a small amount is needed to produce
its effect.
e.
they are polar molecules.
39. Steroid hormones and thyroid hormones do not require a membrane receptor 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 of the membranes.
40. 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.
41. When a ___ hormone carrier protein complex contacts the surface of a cell, the hormone is released
and penetrates directly through the plasma membrane.
a.
peptide
b.
steroid
c.
protein
d.
peptide and protein
e.
peptide, steroid, and protein
42. Various viruses support their propagation by activating ____ kinase cascades in cells they infect.
a.
MAP
d.
GTP
b.
cAMP
e.
cytoplasmic
c.
steroid hormone
43. A common second messenger molecule is
a.
a steroid compound.
b.
cyclic AMP.
c.
ADP.
d.
prostaglandin.
e.
intermedin.
44. 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
45. How a male rat behaves toward a female has been shown to alter ____ in her brain, presumably then
activating ___ receptors in some neurons.
a.
peptide hormones; neurotransmitter
d.
neurotransmitter release; testosterone
b.
neurotransmitter release; steroid hormone
e.
neurotransmitter release; peptide hormone
c.
cAMP kinases; steroid hormone
46. In general, a cell receiving a message undergoes three stages of cell signaling. The stages are ____.
a.
the paracrine, autocrine, and local stages.
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 stages
47. The insulin receptor is an example of ____.
a.
a G protein coupled receptor
b.
a hydrophobic receptor
c.
a hormone receptor
d.
a receptor tyrosine kinase
e.
an ion channel receptor
Select the Exception
48. Cells communicate with each other by various mechanisms. All of the following are examples of ways
cells communicate EXCEPT ____.
a.
gap junctions
b.
transfer chain proteins
c.
recognition of specific membrane surface molecules
d.
cell adhesion molecules
e.
chemical messengers
49. Each of the following is a type of cell surface receptor EXCEPT ____.
a.
receptor tyrosine kinases
b.
enzyme-linked receptors
c.
G protein coupled receptors
d.
steroid hormone receptors
e.
chemically-gated ion channels
50. Binding of the peptide hormone insulin to its receptor tyrosine kinase results in each of the following
cellular activities EXCEPT ____.
a.
cell division
b.
glucose uptake
c.
regulation of metabolic reactions
d.
cell growth
e.
photosynthesis
51. All of the following are true of cell communication systems EXCEPT ____.
a.
cell signaling occurred early in the evolution of life
b.
communicating cells may be found far apart or adjacent to each other
c.
most signal receptors are found bound to the outer nuclear membrane
d.
protein phosphorylation is a major mechanism of signal transduction
e.
in response to a signal, a cell can impact transcription of RNA
52. Each of the following are steps in the receptor kinase signaling pathway EXCEPT ____.
a.
a signal molecule binds to a membrane receptor protein
b.
protein kinase is activated
c.
GTP donates a phosphate group to an inactive protein kinase
d.
a specific protein is activated via phosphorylation
e.
a cellular response is initiated
53. All of the following statements apply to G proteins EXCEPT ____.
a.
G proteins transmit a signal from the cell surface to the interior of the cell
b.
all G proteins have a similar structure
c.
G proteins do not use a second messenger but transmit the signal directly to the nucleus
d.
G proteins act to amplify the signal creating a cascade response in the cell
e.
G proteins are the target of toxins released by some pathogenic bacteria
OTHER
54. Arrange the following steps in the pathway activated by G protein-coupled receptors. Write the letter
of the first step next to 1 and the letter of the last step next to 5.
A.
Activation of effector
B.
Activation of protein kinases
C.
Receptor binds first messenger
D.
Production of second messenger
E.
Activation of G protein
1.
2.
3.
4.
5.
ANS:
SHORT ANSWER
55. Why is it so necessary for cells to communicate with each other in a regulated way?
56. Why is cell communication considered evolutionarily ancient?
57. What is the function of signal transduction?
58. How does a signal molecule bring about specific changes in the cell to which it binds?
59. Amplification is an important characteristic of signal transduction pathways involving surface
receptors. What is amplification and how is it accomplished in the cell?
60. How does cAMP regulate levels of glucose in mammals?
162
MATCHING
Labeling
Label the following components of a surface receptor.
61. extracellular signal molecule
62. site triggering cellular response, when activated
63. transmembrane segment
64. cytoplasmic segment
65. extracellular segment of receptor
66. signal binding site
MODIFIED TRUE/FALSE
If the statement is true, answer "T". If the statement is false, answer "F" and make it correct by
changing the underlined word(s) and writing the correct word(s) in the answer blank(s).
67. The system of communication between cells through signaling pathways is called homeostasis.
68. In the liver, the enzyme glycogen phosphorylase catalyzes the breakdown of glucose.
69. Typically, the signal binding site of a glycoprotein is non-specific.
70. In the binding of a signal molecule to a surface receptor, the signal molecule does not enter the cell.
71. G protein-coupled receptors are found in prokaryotes and eukaryotes.
72. Steroid hormones are nonpolar molecules derived from cholesterol.
73. Cross-talk between second messenger pathways is probably involved in particular types of olfactory
signal transduction in many animals.
ESSAY
74. Differentiate between reception, transduction and response in cell signaling and provide an example.
75. Describe the molecules and processes involved in cell communication control of blood sugar.
