Score for this attempt: 70 out of 80 *
Submitted Mar 8 at 3:13pm
This attempt took 90 minutes.
Question 1
2 / 2 pts
Hydrolysis of ATP by the Na,K-ATPase moves ________ while hydrolysis of the
phosphate moves ________.
3 K+; 2 Na+
2 Na+; 3 K+
2 K+; 3 Na+
C !
3 Na+; 2 K+
none of the above
Question 2
2 / 2 pts
Hormones bind to ________ with ________ affinity.
agonists; high
G proteins; low
antagonists; low
C !
receptors; high
ligands; low
Question 3
2 / 2 pts
Which of the following is a ligand of the β2-adrenergic receptor?
adenosine
tyrosine
C !
norepinephrine
serotonin
caffeine
Question 4
2 / 2 pts
The activity of protein kinase A is affected by which of the following?
I. activated adenylate cyclase
II. levels of cAMP
III. phosphodiesterases
II only
C !
I, II, and III
III only
I only
I and II
Question 5
2 / 2 pts
When a receptor loses its ability to transmit a signal following continuous
exposure to a ligand, the receptor is said to be ________.
saturated
transduced
specific
C !
desensitized
none of the above
Question 6
2 / 2 pts
Desensitization of a G protein-coupled receptor is caused by phosphorylation
of the receptor by a specific kinase. What protein recognizes the
phosphorylated receptor?
phospholipase C
adenosine receptor
cAMP phosphodiesterase
the G protein γ subunit
C !
arrestin
Question 7
2 / 2 pts
Which of the following is true regarding SNARE complex formation?
prior to membrane association, SNARE proteins are in an unfolded state
formation of the SNARE complex is thermodynamically favorable, as is
membrane fusion
two proteins of the SNARE complex come from the membrane and one from
the synaptic vesicle
formation of a four-helix complex is critical for membrane association of the
vesicle
C !
all of the above
Question 8
2 / 2 pts
Which of the following correctly states an essential step in the function of
heterotrimeric G protein function?
C !
Binding of a hormone to a receptor must signal the exchange of GDP for GTP.
Binding of GTP to the receptor protein must induce a change in conformation
of the receptor.
Binding of cAMP to the α subunit of the G protein must initiate translocation
of the subunit.
A cascade of events must occur that ultimately activates protein kinase C.
All of the above are correct.
Question 9
2 / 2 pts
Serotonin reuptake occurs by a(n) ________.
antiporter using Na+
uniporter
C !
symporter using Na+
antiporter using Ca2+
symporter using Ca2+
Question 10
2 / 2 pts
The second messenger ________ is produced by the enzyme ________.
C !
cAMP; adenylate cyclase
inositol diphosphate; phospholipase C
cGMP; GTP cyclase
triacylglycerol; phospholipase C
nitric oxide; arginase
Question 11
2 / 2 pts
Transport of glucose from the intestine into the intestinal cells is
accomplished by a(n) ________. This is an example of ________.
symporter; primary active transport
uniporter; passive transport
C !
symporter; secondary active transport
antiporter; secondary active transport
uniporter; primary active transport
Question 12
2 / 2 pts
The ability for some receptor tyrosine kinases to ultimately activate
phospholipase C is an example of ________.
autophosphorylation
antagonism
C !
cross-talk
desensitization
poor receptor-ligand specificity
Question 13
2 / 2 pts
Which of the following will cause the opening or closing of a gated ion
channel?
phosphorylation
ligand binding
voltage change
pH change
C !
all of the above
Question 14
2 / 2 pts
Which of the following is (are) associated with cAMP binding to cAMP-
dependent protein kinase A (PKA)?
I. cAMP binds to the regulatory subunits.
II. PKA tetrameric regulatory subunits and catalytic subunits dissociate.
III. Catalytic subunits phosphorylate multiple targets with specific serine and
threonine residues.
IV. cAMP is membrane bound via phosphoinositol attachment.
II, III, IV
C !
I, II, III
I, II, III, IV
III, IV
I, II
Question 15
2 / 2 pts
The ________ receptor is a receptor tyrosine kinase.
α1-adrenergic
calmodulin
β2-adrenergic
C !
insulin
cortisol
Question 16
2 / 2 pts
A pore that simultaneously transports two different molecules in different
directions is called ________.
a uniport
a gap junction
an equilibrium channel
a symport
C !
an antiport
Question 17
2 / 2 pts
Which of the following can be a hormone?
polypeptides
steroids
amino acid derivatives
eicosanoids
C !
all of the above
Question 18
2 / 2 pts
Ligand binding to a receptor tyrosine kinase causes ________ of the receptor
which then ________ the next protein in the signaling pathway.
acylation; activates
methylation; hydrolyzes
hydrolysis; inhibits
C !
phosphorylation; phosphorylates
none of the above
Question 19
2 / 2 pts
Which of the following is true regarding the glucose transporter?
it is able to transport glucose into a cell against a concentration gradient
ATP hydrolysis prevents the transporter from working in reverse
C !
binding of glucose causes a conformational change so that the transporter is
never open on both sides of the membrane
in addition to glucose, it will transport any other monosaccharide with six
carbons
none of the above
Question 20
2 / 2 pts
Which of the following occurs during the fusion of a synaptic vesicle and cell
membrane?
C !
selective removal of acyl chains from membrane phospholipids allows the
bilayer to bow outward
the composition of the two membranes has no effect upon the rate of fusion
addition of triacylglycerols to the membrane allows the bilayer to bow inward
SNARE complexes dissociate to allow membrane fusion to occur
none of the above
Question 21
2 / 2 pts
Nerve cells contain high levels of ________ which is a derivative of ________.
phosphatidylethanolamine; palmitic acid
ganglioside GM1; ceramide
C !
sphingomyelin; sphingosine
cholesterol; isoprene
phosphatidylcholine, phosphatidic acid
Question 22
2 / 2 pts
What enzyme is activated by association with an active G protein?
protein kinase G
protein kinase A
cAMP phosphodiesterase
C !
adenylate cyclase
all of the above
Question 23
2 / 2 pts
What two amino acid residues are the targets of protein kinase A?
Tyr and Thr
Ser and Tyr
Asn and Gln
C !
Thr and Ser
Cys and Ser
Question 24
2 / 2 pts
The eicosanoids are derived from the membrane fatty acid ________.
stearic acid
α-linolenic acid
linoleic acid
docosahexaenoic acid (DHA)
C !
arachidonic acid
Question 25
2 / 2 pts
Which of the following is (are) an advantage(s) of protein phosphorylation
regarding biochemical signaling?
I. Phosphorylation is rapid and specific.
II. Phosphorylation is enzymatically reversible.
III. Phosphorylation can be amplified by cascade systems.
IV. Phosphorylation results in covalent modification of enzymes and proteins.
III only
C !
I, II, III, IV
II, III, IV
II, III
I, II
Question 26
2 / 2 pts
Heterotrimeric G proteins ________.
I. consist of three subunits, Gα, Gβ, and Gγ
II. function as an autoinhibtory segment
III. can function as a mediator to adenylate cyclase activity
IV. are anchored to the cytoplasmic side of the membrane
C !
I, III, IV
I, II, IV
I only
I, IV
I, III
Question 27
2 / 2 pts
Which of the following statements regarding membrane transporters is true?
a porin is always open but only transports solutes in one direction
C !
amphotericin is able to assemble inside a membrane in such a manner to
form a channel through which K+ and Na+ flow, thus disrupting the ion
gradient
an ion channel selective for K+ will also allow Na+ through since both are
small enough to fit through the channel
K+ channels can work in both directions, allowing the neuronal action
potential to move in multiple directions
none of the above
Question 28
2 / 2 pts
A sudden increase in the concentration of ________ causes the release of
acetylcholine from the axon of a nerve cell.
H+
Na+
Cl-
K+
C !
Ca2+
Question 29
2 / 2 pts
Which amino acid in the aquaporin channel hydrogen bonds with water to
prevent the movement of protons?
Ile
Leu
Phe
Val
C !
Asn
Question 30
2 / 2 pts
The second messenger ________ opens Ca2+ channels in the endoplasmic
reticulum.
cGMP
cAMP
diacylglycerol
C !
inositol trisphosphate
nitric oxide
Question 31
2 / 2 pts
Which of the following hormones is able to cross biological membranes and
thus the receptor is found inside the cell, not on the cell surface?
epinephrine
glucagon
insulin
C !
cortisol
platelet derived growth factor
Question 32
2 / 2 pts
Which of the following would be the first to occur following opening of
Ca2+ channels during acetylcholine-mediated neurotransmission to a muscle
cell?
reuptake of acetylcholine by the nerve cell
binding of acetylcholine to muscle cell receptors
hydrolysis of acetylcholine by acetylcholinesterase
release of acetylcholine by the nerve cell
C !
binding of SNARE complex to synaptic vesicles and pre-synaptic membrane
Question 33
2 / 2 pts
All known porins are ________ proteins composed of ________.
monomeric; seven transmembrane α-helices
C !
trimeric; β-barrels
dimeric; β-barrels
dimeric; three transmembrane α-helices
trimeric; four transmembrane α-helices
Question 34
2 / 2 pts
Which of the following is an example of nonmediated transport?
passive transport
C !
simple diffusion
active transport
facilitated diffusion
all of the above
Question 35
2 / 2 pts
cAMP binds to the ________ subunits of protein kinase A allowing the tetramer
to dissociate into ________.
regulatory subunits; two active monomers and two inactive monomers
active subunits; two active monomers and an inactive dimer
regulatory subunits; an active dimer and two inactive monomers
active subunits; an active dimer and two inactive monomers
C !
regulatory subunits; two active monomers and an inactive dimer
Question 36
Not yet graded / 5 pts
Explain the importance of membrane rafts in cell signaling pathways.
Your Answer:
Membrane rafts or lipid rafts serve as a sorting platform and hub for signal
transduction proteins. Member rafts are a critical part of the
compartmentalization of signaling pathways. Physical segregation of proteins
in member rafts may modulate the accessibility of proteins to regulatory or
effector molecules. Member rafts may induce conformational changes in
proteins which may affect their activities. Member rafts are essential for the
maintenance of cellular functions such as signal transductions, receptor
activation, intracellular lipid and protein trafficking, endocytosis, and
extracellular vesicle formation.
Question 37
Not yet graded / 5 pts
What is the major difference between gated and nongated ion channels?
Give an example of two different gating signals.
Your Answer:
Nongated ion channels are known as leakage ion channels, in which the
movements of ions are unregulated. Gated ion channels contain gates that
open and close when conformational changes occur in the channel protein. In
gated ion channels, ions are regulated, and they permit movement only
when they are open. Examples of gated ion channels are voltage-gated ion
channels open and close in response to the change in voltage or membrane
potential and Ligand-gated ion channels open when a ligand or chemical
messenger binds with the channel and close when the Ligand is removed.
