1
MOLECULAR BIOLOGY OF THE CELL, SIXTH EDITION CELL
SIGNALING 2026 JUST RELEASED LATEST UPDATE
1. A cell expresses a transmembrane protein that is cleaved at the plasma membrane to
release an extracellular fragment. The fragment binds to receptor proteins on nearby cells and
activates signaling pathways resulting in altered gene expression patterns in the cells. What
form of intercellular signaling does this represent?
A. Contact-dependent signaling
B. Paracrine signaling
C. Synaptic signaling
D. Endocrine signaling
E. Autocrine signaling
Answer- B
2. Which of the following is NOT a common second messenger in cell signaling? A.
Ca2+
B. Cyclic adenosine monophosphate
C. Diacylglycerol
D. Tyrosine
E. Inositol
trisphosphate Answer-
D
3. Which of the following events normally activates a GTP-binding protein? A.
GTP hydrolysis by the protein
B. Activation of an upstream GTPase-activating protein
C. Activation of an upstream guanine nucleotide exchange factor
D. Phosphorylation of a bound GDP molecule by an upstream phosphorylase
E. Pi release after GTP hydrolysis
Answer- C
4. In which of the following schematic drawings of signaling pathways does the activation of the
receptor lead to gene expression? Activating and inhibitory steps are indicated with (+) and (–),
respectively.
,2
Gene Expression (+) (–) (–) (+) (+)
A. Activated receptor activator
Signaling proteins Transcription
Gene Expression (–) (–) (–) (+) (+) B.
(–) (+)
Gene Expression (+) (+) (+)
(+)
C.
(–) (+)
Gene Expression (–) (–) (+)
(–)
D.
(+) (–)
Gene Expression (–) (–) (+)
(+)
E.
Answer- A
Reference: Examples of Cellular Response Curves Questions 5-8
In the following graphs, the cellular response, as measured in real time by the concentration of
a certain active effector protein, is plotted over time for five cell types (A to E) that are treated
with three different concentrations of a signal molecule. During the time period indicated by the
horizontal gray bar, the signal molecule is present in the culture media at a concentration of 1
nM (dotted curve), 5 nM (gray curve), or 25 nM (solid curve). Answer the following question(s)
based on these graphs.
100 0 - 100
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100
MOLECULAR BIOLOGY OF THE CELL, SIXTH EDITION CELL
SIGNALING 2026 JUST RELEASED LATEST UPDATE
1. A cell expresses a transmembrane protein that is cleaved at the plasma membrane to
release an extracellular fragment. The fragment binds to receptor proteins on nearby cells and
activates signaling pathways resulting in altered gene expression patterns in the cells. What
form of intercellular signaling does this represent?
A. Contact-dependent signaling
B. Paracrine signaling
C. Synaptic signaling
D. Endocrine signaling
E. Autocrine signaling
Answer- B
2. Which of the following is NOT a common second messenger in cell signaling? A.
Ca2+
B. Cyclic adenosine monophosphate
C. Diacylglycerol
D. Tyrosine
E. Inositol
trisphosphate Answer-
D
3. Which of the following events normally activates a GTP-binding protein? A.
GTP hydrolysis by the protein
B. Activation of an upstream GTPase-activating protein
C. Activation of an upstream guanine nucleotide exchange factor
D. Phosphorylation of a bound GDP molecule by an upstream phosphorylase
E. Pi release after GTP hydrolysis
Answer- C
4. In which of the following schematic drawings of signaling pathways does the activation of the
receptor lead to gene expression? Activating and inhibitory steps are indicated with (+) and (–),
respectively.
,2
Gene Expression (+) (–) (–) (+) (+)
A. Activated receptor activator
Signaling proteins Transcription
Gene Expression (–) (–) (–) (+) (+) B.
(–) (+)
Gene Expression (+) (+) (+)
(+)
C.
(–) (+)
Gene Expression (–) (–) (+)
(–)
D.
(+) (–)
Gene Expression (–) (–) (+)
(+)
E.
Answer- A
Reference: Examples of Cellular Response Curves Questions 5-8
In the following graphs, the cellular response, as measured in real time by the concentration of
a certain active effector protein, is plotted over time for five cell types (A to E) that are treated
with three different concentrations of a signal molecule. During the time period indicated by the
horizontal gray bar, the signal molecule is present in the culture media at a concentration of 1
nM (dotted curve), 5 nM (gray curve), or 25 nM (solid curve). Answer the following question(s)
based on these graphs.
100 0 - 100
0-
AB 07
,3
100
) r
n
i
e p
t
o
0 7 100
e r
s
o
n t
o c
ps e
,4
e
f
r f
e
r
a f
l
o
u
ll
e
CD n
o
i
t
C
v
a
100
