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Biochem Ch 9

Terms in this set (33)

The concentration of Ca 2+ in the endoplasmic reticulum (outside) is 1 mM, and the concentration of Ca 2+ in the cytosol (inside) is 0.1 µM. Would Ca 2+ movement at 37 o C be more thermodynamically favorable at a membrane potential of -50 mV or at +50 mV? HINT: Watch your units!
At -50 mV
After depolarization of a nerve cell, what event restores the resting potential?

A) K+ efflux
B) K+ influx
C) Na+ efflux
D) Na+ influx
E) Cl- efflux
A
What would occur when the action potential for muscle contraction reaches its terminus, if SNARE complexes were not functioning?

A) Calcium ions would not enter the axon terminus.
B) Acetylcholine would not be packaged into vesicles and would eventually degrade.
C) Muscle contraction would still occur but at a slower rate.
D) Acetylcholine released from the axon terminus would be unable to bind to the receptors on the muscle cell in order to cause contraction.
E) Membrane fusion would not occur and there would be no release of acetylcholine into the synaptic cleft.
E
A sudden increase in the concentration of _____ causes the release of acetylcholine from the axon of a nerve cell.

A) Na+
B) K+
C) Ca2+
D) Cl-
E) H+
C
What factor is primarily responsible for the extremely rapid propagation of axon potential?

A) Na+ channels open quickly to allow Na+ to flood into the cell.
B) K+ channels close quickly to prevent K+ from leaving the cell.
C) Axons are insulated with a myelin sheath which prevents ion movement except at the nodes betweenthe myelinated segments.
D) K+ channels open quickly to allow K+ to enter the cell.
C
ABC transporters are examples of
primary active transport
Kidney cells include two antiport proteins, a H + /Na + exchanger and a Cl - /HCO 3- exchanger. What is the source of free energy that drives the transmembrane movement of all these ions?
secondary active transport
If the pH of the matrix is 7.7, what is the pH of the intermembrane space if the ΔG for transport of H+ is 20 kJ/mol at 37°C with Δψ = 170 mV?
7.1
What type of transport does not require the assistance of a membrane protein?

A) simple diffusion
B) facilitated diffusion
C) passive transport
D) active transport
E) none of the above
A
A pore that simultaneously transports two different molecules in different directions is called:

A) a promiscuous pore
B) a symporter
C) an equilibrium machine
D) an antiporter
E) a gap junction
D
The movement of glucose into a cell when blood sugar is high is accomplished by _____. The movement of K + against its concentration gradient is accomplished by _____.

A) simple diffusion; active transport
B) passive transport; passive transport
C) active transport; membrane potential
D) simple diffusion; passive transport
E) passive transport; active transport
E
Which of the following is true regarding the glucose transporter?

A) in addition to glucose, it will transport any other monosaccharide with six carbons
B) binding of glucose causes a conformational change so that the transporter is never open on both sides of the membrane
C) ATP hydrolysis prevents the transporter from working in reverse
D) it is able to transport glucose into a cell against a concentration gradient
E) none of the above
B
The neurotransmitters dopamine, epinephrine, and norepinephrine are synthesized from the amino acid ______.

A) tryptophan
B) tyrosine
C) phenylalanine
D) glutamine
E) aspartate
B
What is the membrane potential created by a sodium gradient where [Na+]out = 145 mM and [Na+]in = 12mM at 37 C?

A) 67 mV
B) 7.9 mV
C) -7.9 mV
D) -29 mV
E) -67 mV
E
What is the ratio [Na+]in/[Na+]out created by depolarization in a nerve cell if the final potential is +50 mV at 37 C?

A) 6.4 106
B) 6.5
C) 1.5
D) 0.15
E) 1.6 10-7
B
Inside a nerve cell at rest, [Na+] is _____ and [K+] _____ relative to the concentrations seen outside the cell.

A) high; high
B) high; low
C) low; high
D) low; low
E) low; equal
C
Nerve cells contain high levels of _____ which is a derivative of _____.

A) phosphatidylethanolamine; palmitic acid
B) cholesterol; isoprene
C) phosphatidylcholine, phosphatidic acid
D) sphingomyelin; sphingosine
E) ganglioside GM1; ceramide
D
For a cell with [Na+]out = 150 mM and [Na+]in = 15 mM at 37 C, what is the free energy for movement of sodium ions from outside the cell to inside if the potential across the membrane is -60 mV?

A) 11.7 kJ/mol
B) 0.145 kJ/mol
C) -0.145 kJ/mol
D) -11.7 kJ/mol
E) cannot be calculated from given information
D
All known porins are _____ proteins composed of _____.

A) monomeric; seven transmembrane -helices
B) dimeric; -barrels
C) dimeric; three transmembrane -helices
D) trimeric; -barrels
E) trimeric; four transmembrane -helices
D
Which of the following will cause the opening or closing of a gated ion channel?

A) pH change
B) phosphorylation
C) voltage change
D) ligand binding
E) all of the above
E
Which of the following statements regarding membrane transporters is true?

A) a porin is always open but only transports solutes in one direction
B) an ion channel selective for K+ will also allow Na+ through since both are small enough to fit through the channel
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
D) K+ channels can work in both directions, allowing the neuronal action potential to move in multiple directions
E) none of the above
C
Which amino acid in the aquaporin channel hydrogen bonds with water to prevent the movement of protons?

A) Asn
B) Leu
C) Phe
D) Val
E) Ile
A
What is a transporter that moves two different molecules or ions in the same direction?

A) uniporter
B) diporter
C) symporter
D) antiporter
E) none of the above
C
The Na,K-ATPase is a(n) _____ that moves Na+ from _____ and K+ from _____.

A) antiporter; inside to out; outside to in
B) antiporter; outside to in; inside to out
C) symporter; inside to out; inside to out
D) symporter; outside to in; outside to in
E) none of the above
A
Hydrolysis of ATP by the Na,K-ATPase moves _____ while hydrolysis of the phosphate moves _____.

A) 3 Na+; 2 K+
B) 2 Na+; 3 K+
C) 3 K+; 2 Na+
D) 2 K+; 3 Na+
E) none of the above
A
The P-glycoprotein is an example of a(n) _____ which has been linked to drug resistance in the treatment of _____.

A) ABC transporter; bacterial infections
B) ABC transporter; cancer
C) Na,K-ATPase; viral infections
D) Na,K-ATPase; parasitic infections
E) none of the above
B
Transport of glucose from the intestine into the intestinal cells is accomplished by a(n) ________. This is an example of ___________.

A) uniporter; passive transport
B) uniporter; primary active transport
C) symporter; primary active transport
D) symporter; secondary active transport
E) antiporter; secondary active transport
D
Which of the following would be the first to occur following opening of Ca2+ channels during acetylcholine-mediated neurotransmission to a muscle cell?

A) binding of SNARE complex to synaptic vesicles and pre-synaptic membrane
B) binding of acetylcholine to muscle cell receptors
C) reuptake of acetylcholine by the nerve cell
D) hydrolysis of acetylcholine by acetylcholinesterase
E) release of acetylcholine by the nerve cell
A
Which type of ion channel is blocked by lidocaine, a local anesthetic?

A) K+
B) Na+
C) pre-synaptic Ca2+
D) post-synaptic Ca2+
E) none of the above
B
Serotonin reuptake occurs by a(n) _____.

A) uniporter
B) antiporter using Na+
C) antiporter using Ca2+
D) symporter using Na+
E) symporter using Ca2+
D
Which of the following is true regarding SNARE complex formation?

A) prior to membrane association, SNARE proteins are in an unfolded state
B) two proteins of the SNARE complex come from the membrane and one from the synaptic vesicle
C) formation of a four-helix complex is critical for membrane association of the vesicle
D) formation of the SNARE complex is thermodynamically favorable, as is membrane fusion
E) all of the above
E
Which of the following occurs during the fusion of a synaptic vesicle and cell membrane?

A) SNARE complexes dissociate to allow membrane fusion to occur
B) addition of triacylglycerols to the membrane allows the bilayer to bow inward
C) selective removal of acyl chains from membrane phospholipids allows the bilayer to bow outward
D) the composition of the two membranes has no effect upon the rate of fusion
E) none of the above
C
The total concentration of receptors in a sample is 20 mM. The concentration of free ligand (L) is 5 mM and Kd is 10 mM. Calculate the percentage of receptors that are occupied by ligand.

A) 67%
B) 33%
C) 25%
D) 75%
E) 50%
B
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