BCH 369 TEST 3 QUESTIONS WITH
ALL ANSWERS CERTIFIED
Which of the following accurately describes the lipid bilayer in biological membranes?
A) The bilayer is stabilized by hydrophilic interactions between the polar lipid head
groups and the aqueous environment.
B) Integral membrane proteins enhance the stability of membrane lipid bilayers.
C) The thickness of membrane bilayers varies slightly, depending on the fatty acids
incorporated in the lipids.
D) Individual lipid molecules flip-flop rapidly between leaflets of the bilayer. - Answer-C)
The thickness of membrane bilayers varies slightly, depending on the fatty acids
incorporated in the lipids
Which of the following would REDUCE a hormone signal mediated via the G protein
signal transduction system?
A) Addition of a substance that activates protein phosphatases.
B) Addition of a substance that inhibits phosphodiesterase.
C) Addition of a substance that activates adenylate cyclase.
D) A and C - Answer-A) Addition of a substance that activates protein phosphatases.
Phorbol esters, which are compounds isolated from plants, are structurally similar to
diacylglycerol. How does the addition of phorbol esters affect the signaling pathways of
cells in culture?
A) They would elevate the concentration of cAMP.
B) They would activate protein kinase A.
C) They would activate protein kinase C.
D) They would activate Ras protein.
E) They would stimulate lipid hormone signaling. - Answer-C) They would activate
protein kinase C.
Which of the following statements is/are TRUE regarding the molecule shown?
1. This molecule is a membrane lipid.2. This molecule contains a carbon-carbon double
bond.3. This molecule is unsaturated.
A) 1 and 2 B) 1 and 3 C) 2 and 3 D) 1, 2 and 3 - Answer-C) 2 and 3
The oxyanion hole in serine proteinases illustrates which of the following mechanisms of
enzyme
action?
A) Induced fit in substrate binding.
C) The role of serine side chains in proteolysis.
B) Reduction of the activation energy barrier.
D) Preferential transition state binding. - Answer-D) Preferential transition state binding.
, Which of the following would be the first to occur following opening of Ca2+ channels
during
acetylcholine-mediated neurotransmission to a muscle cell?
A) reuptake of acetylcholine by the nerve cell
B) release of acetylcholine by the nerve cell
C) binding of SNARE complex to synaptic vesicles and pre-synaptic membrane
D) hydrolysis of acetylcholine by acetylcholinesterase
E) binding of acetylcholine to muscle cell receptors - Answer-C) binding of SNARE
complex to synaptic vesicles and pre-synaptic membrane
In the absence of allosteric effectors, the enzyme phosphofructokinase displays
Michaelis-Menten kinetics.The v0/Vmax ratio is 0.9 when the concentration of its
substrate, fructose-6-phosphate, is 0.10
mM. What is the KM for substrate under these conditions?
A) 11 mM B) 22 mM C) 11 µM D) 0.08 µM E) 1.0 mM - Answer-C) 11 µM
A galactosyl transferase that catalyzes the reaction below, β3-GalT, has recently been
purified. The reaction velocity was measured in the presence of UDP-[3H]Gal. Use the
graph below to determine the value of KM and Vmax.
A) KM = 2.27 mM; Vmax = 0.26 µM/h
D) KM = 590 µM; Vmax = 2.27 x 103 µM/h
B) KM = 3.8 mM; Vmax = 0.26 µM/h
E) KM = 590 µM; Vmax = 4.41 x 104 µM/h
C) KM = 3.8 µM; Vmax = 2.27 x 10-3 µM/h - Answer-D) KM = 590 µM; Vmax = 2.27 x
103 µM/h
The drug known as Botox is a preparation of botulinum toxin. How does this account for
its use by
plastic surgeons to alleviate facial wrinkles?
A) botulinum toxin targets SNAREs for degradation by proteolysis.
B) SNAREs are necessary for transmission of signals from facial nerves to muscles via
synaptic.
C) SNAREs function by forming α−helical bundles to fuse synaptic vesicles with the
plasma membrane
D) all of the above
E) none of the above - Answer-D) all of the above
If the (Na+,K+)-ATPase transporter were modified so that it could no longer be
phosphorylated, which
of the following would happen?
A) No ions would be transported.
B) K+ ions but not Na+ ions would be transported.
C) Na+ ions but not K+ ions would be transported.
ALL ANSWERS CERTIFIED
Which of the following accurately describes the lipid bilayer in biological membranes?
A) The bilayer is stabilized by hydrophilic interactions between the polar lipid head
groups and the aqueous environment.
B) Integral membrane proteins enhance the stability of membrane lipid bilayers.
C) The thickness of membrane bilayers varies slightly, depending on the fatty acids
incorporated in the lipids.
D) Individual lipid molecules flip-flop rapidly between leaflets of the bilayer. - Answer-C)
The thickness of membrane bilayers varies slightly, depending on the fatty acids
incorporated in the lipids
Which of the following would REDUCE a hormone signal mediated via the G protein
signal transduction system?
A) Addition of a substance that activates protein phosphatases.
B) Addition of a substance that inhibits phosphodiesterase.
C) Addition of a substance that activates adenylate cyclase.
D) A and C - Answer-A) Addition of a substance that activates protein phosphatases.
Phorbol esters, which are compounds isolated from plants, are structurally similar to
diacylglycerol. How does the addition of phorbol esters affect the signaling pathways of
cells in culture?
A) They would elevate the concentration of cAMP.
B) They would activate protein kinase A.
C) They would activate protein kinase C.
D) They would activate Ras protein.
E) They would stimulate lipid hormone signaling. - Answer-C) They would activate
protein kinase C.
Which of the following statements is/are TRUE regarding the molecule shown?
1. This molecule is a membrane lipid.2. This molecule contains a carbon-carbon double
bond.3. This molecule is unsaturated.
A) 1 and 2 B) 1 and 3 C) 2 and 3 D) 1, 2 and 3 - Answer-C) 2 and 3
The oxyanion hole in serine proteinases illustrates which of the following mechanisms of
enzyme
action?
A) Induced fit in substrate binding.
C) The role of serine side chains in proteolysis.
B) Reduction of the activation energy barrier.
D) Preferential transition state binding. - Answer-D) Preferential transition state binding.
, Which of the following would be the first to occur following opening of Ca2+ channels
during
acetylcholine-mediated neurotransmission to a muscle cell?
A) reuptake of acetylcholine by the nerve cell
B) release of acetylcholine by the nerve cell
C) binding of SNARE complex to synaptic vesicles and pre-synaptic membrane
D) hydrolysis of acetylcholine by acetylcholinesterase
E) binding of acetylcholine to muscle cell receptors - Answer-C) binding of SNARE
complex to synaptic vesicles and pre-synaptic membrane
In the absence of allosteric effectors, the enzyme phosphofructokinase displays
Michaelis-Menten kinetics.The v0/Vmax ratio is 0.9 when the concentration of its
substrate, fructose-6-phosphate, is 0.10
mM. What is the KM for substrate under these conditions?
A) 11 mM B) 22 mM C) 11 µM D) 0.08 µM E) 1.0 mM - Answer-C) 11 µM
A galactosyl transferase that catalyzes the reaction below, β3-GalT, has recently been
purified. The reaction velocity was measured in the presence of UDP-[3H]Gal. Use the
graph below to determine the value of KM and Vmax.
A) KM = 2.27 mM; Vmax = 0.26 µM/h
D) KM = 590 µM; Vmax = 2.27 x 103 µM/h
B) KM = 3.8 mM; Vmax = 0.26 µM/h
E) KM = 590 µM; Vmax = 4.41 x 104 µM/h
C) KM = 3.8 µM; Vmax = 2.27 x 10-3 µM/h - Answer-D) KM = 590 µM; Vmax = 2.27 x
103 µM/h
The drug known as Botox is a preparation of botulinum toxin. How does this account for
its use by
plastic surgeons to alleviate facial wrinkles?
A) botulinum toxin targets SNAREs for degradation by proteolysis.
B) SNAREs are necessary for transmission of signals from facial nerves to muscles via
synaptic.
C) SNAREs function by forming α−helical bundles to fuse synaptic vesicles with the
plasma membrane
D) all of the above
E) none of the above - Answer-D) all of the above
If the (Na+,K+)-ATPase transporter were modified so that it could no longer be
phosphorylated, which
of the following would happen?
A) No ions would be transported.
B) K+ ions but not Na+ ions would be transported.
C) Na+ ions but not K+ ions would be transported.
