Chapter 13 Signal-Transduction Pathways
Matching Questions
Use the following to answer questions 1–10:
Choose the correct answer from the list below. Not all of the answers will be used.
a) protein kinase A (PKA)
b) calmodulin
c) fatty acids
d) proto-oncogene
e) R2C2
f) R1C2
g) cAMP
h) phospholipase C
i) protein kinase C (PKC)
j) epinephrine
k) oncogene
l) small G proteins
1.
____________ The primary messenger responsible for the “fight or flight” response.
2.
The enzyme that becomes active when bound to cAMP is ____________.
Ans: a
Section: 13.2
3.
____________ The and subunits of heterotrimeric G proteins are anchored to the cell
membrane by being covalently linked to these types of molecules.
Ans: c
Section: 13.2
4.
The ____________ enzyme becomes active when bound to Ca2+ and diacylglycerol.
Ans: i
Section: 13.2
5.
The inactive form of protein kinase A is ____________.
Ans: e
6.
Ras is a member of the ____________ family of proteins.
Ans: l
Section: 13.3
7.
____________ A gene that leads to the transformation of susceptible cell types into cell types
with cancer-like characteristics.
Ans: k
Section: 13.6
Ans: j
Section: 13.2
Chapter 13 Signal Transduction Pathways
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8.
The ____________ protein binds to calcium ions and serves as a Ca2+ sensor in eukaryotic cells.
9.
The ____________ molecule functions as a secondary messenger.
Ans: g
Section: 13.2
10.
____________ The enzyme that catalyzes the cleavage of PIP2.
Ans: h
Section: 13.2
Fill–in-the-Blank Questions
11.
Protein kinase A phosphorylates serine and residues.
Ans: threonine Section: 13.2
12.
is the membrane protein that catalyzes the conversion of ATP to cAMP.
Ans: Adenylate cyclase Section: 13.2
13.
The cytosolic side, or β subunit, of the insulin receptor is a kinase.
Ans: tyrosine Section: 13.4
14.
The receptor undergoes dimerization and cross-phosphorylation when activated.
Ans: EGF Section: 13.3
15.
is a secondary messenger and is abbreviated IP3.
Ans: Inositol 1,4,5-trisphosphate Section: 13.1
16.
7TM is an abbreviation for receptors.
Ans: seven-transmembrane-helix Section: 13.2
17.
binds to β-andrenergic receptors.
Ans: Epinephrine or adrenaline Section: 13.2
18.
The binding of IP3 to the IP3 receptor results in the release of from the endoplasmic
reticulum.
Ans: calcium ions Section: 13.2
19.
When activated, the insulin receptor results in the mobilization of transporters to the cell
surface.
Ans: glucose Section: 13.4
20.
The is a calcium-binding unit in many proteins and is characterized by a helix-loop-helix
structure.
Ans: EF hand Section: 13.5
Ans: b
Section: 13.5
Chapter 13 Signal Transduction Pathways
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Multiple-Choice Questions
21.
Most signal molecules:
A)
easily diffuse through the membrane and bind to a receptor in the cytoplasm.
B)
bind to membrane receptors and transmit information across a membrane without
traversing the membrane.
C)
carry out functions in the nucleus after binding to a receptor in the cell membrane.
D)
A and C.
E)
A, B, and C.
22.
Examples of second messengers include:
A)
cAMP.
B)
calcium ion.
C)
diacylglycerol.
D)
A and B.
E)
A, B, and C.
Ans: E Section: 13.1
23.
Advantages of second messengers include:
A)
the signal can be amplified by making many second messengers.
B)
can freely diffuse to other sites within the cell.
C)
a few common second messengers can be used in multiple signaling pathways.
D)
All of the above.
E)
None of the above.
Ans: D Section: 13.1
24.
Which of the following amino acids can be phosphorylated?
A)
tyrosine, serine, threonine
B)
tyrosine, serine, tryptophan
C)
serine, threonine, asparagine
D)
histidine, serine, phenylalanine
E)
tyrosine, methionine, tryptophan
Ans: A Sections: 13.2 and 13.3
25.
Which form of the guanyl nucleotide is bound in the unactivated state?
GTP
GDP
GMP
dGTP
None of the above.
Ans: B Section: 13.2
26.
The mechanism by which insulin-signaling processes might be terminated includes:
A)
change in temperature.
B)
the aggregation of all protein subunits.
C)
protein dephosphorylation by phosphatases.
D)
All of the above.
E)
None of the above.
Ans: C Section: 13.4
Ans: B Section: 13.1
Chapter 13 Signal Transduction Pathways
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27.
How does the binding of a hormone to a receptor activate a G-protein?
A)
It causes an exchange of GTP for bound GDP.
B)
It causes the γ subunit to be released from binding to the β subunit.
C)
It causes an exchange of GDP for bound GTP.
D)
A and B.
E)
None of the above.
28.
Why is bound GTP considered a “clock”?
A)
It behaves in specific time intervals.
B)
GTP is exchanged for GDP after binding to adenylate cyclase.
C)
The G receptors have intrinsic GTPase activity, hydrolyzing GTP to GDP and Pi.
D)
All of the above.
E)
None of the above.
Ans: C Section: 13.2
29.
The enzyme responsible for induction of the phosphoinositide cascade is:
A)
phospholipase C.
B)
phospholipase A.
C)
C-dependent protein (CDP).
D)
All of the above.
E)
None of the above.
Ans: A Section: 13.2
30.
What are the two messenger products formed by cleavage of PIP2?
A)
diacylglyercol and inositol 1,4,5-triphosphate
B)
diacylglyercol and inositol 1,3,5-triphosphate
C)
diacylglyercol and inositol 1,3-diphosphate
D)
diacylglyercol phosphate and inositol 1,4,5-trisphosphate
E)
None of the above.
Ans: A Section: 13.2
31.
How is calmodulin activated?
A)
by binding of both calcium and potassium
B)
by binding Ca2+ when the cytosolic concentration is raised
C)
by binding to a positively charged helix on another protein
D)
All of the above.
E)
None of the above.
Ans: B Section: 13.5
32.
Cross-phosphorylation is possible when two receptor proteins with kinase domains
A)
are cleaved.
B)
form dimers.
C)
are internalized into organelles.
D)
All of the above.
E)
None of the above.
Ans: B Section: 13.4
Ans: A Section: 13.1
Chapter 13 Signal Transduction Pathways
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33.
Example(s) of disease(s) caused by altered G-protein activity include
A)
whooping cough.
B)
cholera.
C)
diabetes.
D)
A and B.
E)
B and C.
34.
______________ may be effective anti-cancer drugs.
A)
Monoclonal antibodies against offending receptors
B)
EGF mimics
C)
Protein kinase inhibitors
D)
All of the above.
E)
Both A and C.
Ans: C Section: 13.6
35.
When insulin binds to its receptor, which of the following occurs?
A)
A PIP2-dependent kinase is activated.
B)
Calmodulin binds to Ca2+.
C)
Sos stimulates the exchange of GTP for GDP.
D)
All of the above.
E)
None of the above.
Ans: A Section: 13.4
36.
Which of the five steps in the generalized scheme of transduction pathways is defective in
Cushing Syndrome?
A)
termination
B)
release of primary messenger
C)
relay of information by second messenger
D)
reception of primary messenger
E)
activation of effectors
Ans: E Section: 13.2
37.
That Gα subunits have intrinsic GTPase activity is important in which of the five steps in the
generalized scheme of transduction pathways?
A)
termination
B)
release of primary messenger
C)
relay of information by second messenger
D)
reception of primary messenger
E)
activation of effectors
Ans: A Section: 13.2
Ans: D Sections: 13.2
Chapter 13 Signal Transduction Pathways
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38.
The cleavage of PIP2 is important in which of the five steps in the generalized scheme of
transduction pathways?
A)
termination
B)
release of primary messenger
C)
relay of information by second messenger
D)
reception of primary messenger
E)
activation of effectors
39.
7TM proteins action is important in which of the five steps in the generalized scheme of
transduction pathways?
A)
termination
B)
release of primary messenger
C)
relay of information by second messenger
D)
reception of primary messenger
E)
activation of effectors
Ans: D Section: 13.3
Short-Answer Questions
40.
What are some of the common structural features of the receptors to which signal molecules
bind?
change into another form (transduced) that affects the shape of the intracellular portion so
the signal can be transmitted.
Section: 13.1
41.
What is a disadvantage of using common molecules for signaling paths?
and sensitive responses can result. However, when the cross talk becomes inappropriate,
the signaling paths and responses will be in error.
Section: 13.1
42.
What happens when signaling paths are not terminated properly?
Ans:
The cell will not be able to respond properly to new stimuli. The errant signals may lead
to cancer, uncontrolled cell growth, or other problems.
Section: 13.1
43.
How many 7TM membranes are there? What are some of their functions?
physiological control, exocytosis, chemotaxis, neurotransmission, cell development and
growth, and viral infection. (See Table 13.1 of the textbook for a complete list.)
Section: 13.2
44.
What is the general mechanism for signal transmission by 7TM receptors?
conformation change that is detectable on the cytoplasmic side of the cell.
Section: 13.2
Ans: C Section: 13.2
Chapter 13 Signal Transduction Pathways
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45
How does binding of epinephrine initiate the cAMP production? Discuss briefly in terms of
receptor structure and function.
46.
How is the hormone-bound activated receptor reset after activation?
bind the hormone, depending on the concentration in the environment.
Section: 13.2
47.
What are receptor tyrosine kinases? Provide an example.
Ans:
These are proteins that bind ligands, such as EGF or insulin, on the extracellular domain.
They also contain tyrosine kinase domains on the intracellular side.
Section: 13.3
48.
Describe how phosphatidylinositol-4,5-diphosphate is converted into two secondary
messengers.
allowing Ca2+ to be released from the cellular stores.
Section: 13.2
49.
What is the difference between a proto-oncogene and an oncogene?
under normal conditions, tend to regulate cell growth. When a proto-oncogene suffers a
mutation that leads to unrestrained growth, it is referred to as an oncogene.
Section: 13.6
50.
What is meant by an EF hand? Draw or describe the structure.
Figure 13.15 of the textbook shows an example of what this structure might look like.
Section: 13.5
enzyme, resulting in a more catalytically active form; thus, more cAMP is made. See
Figure 13.4 of the textbook for more detail.
Section: 13.2
Chapter 13 Signal Transduction Pathways
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51.
Give the reaction catalyzed by tyrosine kinase.
52.
What steps lead from the activation of a cross-phosphorylated receptor tyrosine kinase to an
activated small G protein such as Ras?
Sos. Sos stimulates the exchange of GTP for GDP in Ras.
Section: 13.3 and Figure 13.16
53.
What is the difference between heterotrimeric G proteins and small G proteins?
activation causes the exchange of GDP for GTP to convert it into an active kinase.
Sections: 13.2 and 13.3
54.
Describe the role of phosphoinositol 4,5-bisphosphate (PIP2) in insulin signal transduction.
which phosphorylates and activates other kinases in the pathway.
Section: 13.4
55.
Why are mutated or overexpressed receptor tyrosine kinases frequently observed in tumors?
the cell.
Section: 13.6
Section: 13.3