Homework Questions: Exam 3 Flashcards
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) binding of glucose causes a conformational change so that the transporter is never open on both sides of the membrane
which of the following statements most accurately defines the term “symport”?
a) a protein which transports two substances in the same direction
b) a protein which transports two substances in the same direction up their concentration gradients
c) a protein which transports two substances in opposite directions up their concentration gradients
d) a protein which transports two substances in opposite directions
a) a protein which transports two substances in the same direction
which of the following statements most accurately defines the term “antiport”?
a) a protein which transports two substances in the same direction
b) a protein which transports two substances in the same direction up their concentration gradients
c) a protein which transports two substances in opposite directions
d) a protein which transports two substances in opposite directions up their concentration gradients
c) a protein which transports two substances in opposite directions
which of the following statements correctly distinguishes transporters (carrier proteins) from porins and ion channels?
a) transporters exhibit a conformational change when substrate binds but porins and ion channels do not
b) porins and ion channels have permanent hole that passes from one side of the membrane to the other through which solutes pass whereas transporters do not
c) porins and ion channels mediate passive transport, while transporters are associated with both passive and active transport
d) both A and B are correct
e) all of the above are correct
e) all of the above are correct
an ion transport protein constructed entirely from B strands is most likely to be…
a) a porin
b) a gated ion channel
c) an aquaporin
d) an active transport pump
a) a porin
The compound 6-O-benzyl-D-galactose competes with glucose for binding to the glucose transporter. The figure below shows the kinetics of glucose transport with an without the inhibitor. How would the Km and Vmax values of it compare to those estimated for glucose?
a) Km would decrease; Vmax would decrease
b) Km would be unchanged; Vmax would increase
c) Km would increase; Vmax would increase
d) Km would increase; Vmax would be unchanged
d) Km would increase; Vmax would be unchanged
the Na,K-ATPas is a(n) _________ that moves Na+ from ________ and K+ from ________.
antiporter; inside to out; outside to in
If the (Na+-K+)=ATPase transporter were modified so that it could no longer be phosphorylated, which of the following would happen?
a) K+ ions but not Na+ ions would be transported
b) Na+ ions but not K+ ions would be transported
c) no ions would be transported
d) ions would be transported down their concentration gradient
c) no ions would be transported
given what you know about the function of the (Na+-K+)-ATPase, which of the following is the most accurate prediction of the structure of its binding site? The binding site is likely to contain multiple:
a) glu and asp residues
b) lys and arg residues
c) ser and thr residues
d) gln and asn residues
e) both c and d
a) glu and asp residues
the primary active transport is usually driven by ________, and secondary active transport by ________.
ATP; an ion gradient
the (Na+-K+)-ATPase works through changes in conformation. Which of the following mechanisms is responsible for these changes in conformation?
a) induced fit
b) cooperatively
c) allostery
d) phosphorylation
d) phosphorylation
the conformational changes responsible for ion transport in the Na,K-ATPase are triggered by…
a) attachment and release of a phosphoryl group
b) Na+ binding and K+ release
c) ATP binding and dissociation
d) Na+ binding
a) attachment and release of a phosphoryl group
an ion will spontaneously move..
a) toward ions with the same charge
b) from an area of high enthalpy to an area of low enthalpy
c) wherever a protein pushes it
d) to an area where it is less concentrated
d) to an area where it is less concentrated
after depolarization of a nerve cell, what event restores the resting potential?
a) K+ efflux
b) Na+ influx
c) Cl- efflux
d) K+ influx
e) Na+ efflux
a) K+ efflux
the main difference between active and passive transport systems is…
a) the source of free energy that drives the transport
b) the structure of the membrane transport protein
c) the types of solutes that are transported
d) the importance of the transport of the cell’s usual activities
a) the source of free energy that drives the transport
Which of the following statements best describes why electrons from FADH2 moving through the electron transport chain contribute less to the proton gradient than electrons from NADH?
a) FADH2 is a prosthetic grou[
b) FADH2 passes its electrons directly to complex III therefore bypassing a portion of the electron transport chain
c) FADH2 has a higher reduction potential than NADH and therefore its electrons must enter the electron transport chain downstream of NADH
d) FADH2 has a lower reduction potential than NADH and therefore its electrons must enter the electron transport chain downstream of NADH
c) FADH2 has a higher reduction potential than NADH and therefore its electrons must enter the electron transport chain downstream of NADH
what does the reduction potential of 0.815 V for the reduction of water to oxygen indicate?
a) water is very strong reducing agent
b) water is a very strong reducing agent and oxygen is a very stand oxidizing agent
c) oxygen is a very strong oxidizing agent
d) water will be spontaneously reduced to oxygen
e) none of the above
c) oxygen is a very strong oxidizing agent
if the reduction potential of NAD+ is -0.315 V and the reduction potential for oxygen is 0.815 V, what is the potential for the oxidation of NADH by oxygen?
1.13 V
acetoacetate may be reduced to 3-hydroxybutyrate. what serves as a better reducing agent?
a) NADH
b) FADH2
a) NADH
the myoglobin and cytochrome c oxidase content were determined in several animals - hare, sheep, ox, and horse. the levels of both proteins were roughly correlated, i.e., the higher the myoglobin content, the greater the cytochrome c oxidase activity. What conclusions can be drawn about the relationship between the two proteins?
a) the two proteins must interact with one another in some biochemical process
b) the two proteins operate independent of biochemical processes
c) the two proteins inhibit one another
d) none of the above
a) the two proteins must interact with one another in some biochemical process
for every two electrons transferred from NADH to oxygen, ______ protons are pumped from the matrix to the inter membrane space.
10
what is the path of electrons from NADH through the electron transport chain?
a) NADH, Complex I, Q, Complex II, CytC, Complex IV, O2
b) NADH, Complex II, Q, Complex III, CytC, Complex IV, O2
c) NADH, Complex I, Q, Complex III, CytB, Complex IV, O2
d) NADH, Complex I, Q, Complex III, CytC, Complex IV, O2
d) NADH, Complex I, Q, Complex III, CytC, Complex IV, O2
ubiquinone is a ________ molecule that serves as a ______ electron carrier; cytochrome c is a ________ molecule that serves as a ______ electron carrier
hydrophobic; 2; hydrophilic; 1
the consumption of acetyl-CoA by the citric acid cycle is DECREASED under which of the following conditions?
a) the concentration of NAD+ is high
b) NADH is rapidly re-oxidized via the electron transport chain
c) the mitochondrial ATP synthase is inactive
d) the concentration of oxaloacetate is high
c) the mitochondrial ATP synthase is inactive
complex III accepts electrons from ________ and transfers them to ________
ubiquinol; cytochrome c
electrons from FADH2 are delivered to _________, and electrons from NADH are delivered to ________ of the electron transport chain
complex II; complex I
what free radical is thought to be commonly produced by electron transport chain?
a) hydroxyl
b) peroxyl
c) superoxide
d) hydrogen peroxyl
e) all of the above
c) superoxide
the cytochromes undergo which oxidation reactions?
Fe2+ —–> Fe3+
why does re-oxidation of FADH2 via electron transport chain ultimately produce fewer molecules of ATP than the re-oxidation of NADH?
a) a smaller H+ gradient is generated when FADH2 is oxidized compared to that generated by oxidation of NADH
b) a larger H+ gradient is generated when FADH2 is oxidized compared to that generated by oxidation of NADH
c) electrons from NADH do not pass through complex II
d) electrons from FADH2 do not pass through complex II
a) a smaller H+ gradient is generated when FADH2 is oxidized compared to that generated by oxidation of NADH
which of the following is NOT associated with electron transport?
a) heme group
b) coenzyme Q
c) coenzyme A
d) iron-sulfur clusters
e) flavin mononucleotide
c) coenzyme A
Apolipoproteins are amphipathic because ___________.
a) they are composed of hydrophilic and hydrophobic regions
b) the transport lipids in an aqueous environment
c) they degrade lipids
d) they are involved in lipid biosynthesis
e) A and B
e) A and B
why is ATP consumed in the initial stage of fatty acid breakdown?
a) ATP drives the active transport of fatty acids into mitochondria
b) ATP is required to link fatty acids to coenzyme A
c) the first step of breakdown is a kinase-catalyzed phosphorylation
d) ATP provides oxidizing power for B-oxidation
b) ATP is required to link fatty acids to coenzyme A
during B-oxidation in the peroxisome, what reoxidizes the enzyme-bound FADH2 during the first oxidation of the pathway?
a) H2O2
b) O2
c) NAD+
d) FMN
e) none of the above
b) O2
each round of B-oxidation of a saturated fatty acyl-CoA produces…
1 NADH, 1 QH2, 1 acetyl-CoA
oxidation of an unsaturated fatty acid requires an additional step catalyzed by a ___________.
a) reductase
b) hydratase
c) synthetase
d) thiolase
a) reductase
if the fatty acid 16:0 is catabolized completely, to carbon dioxide and water, the net yield of ATP per molecule of fatty acid is:
130 ATP
the hydrolysis of triacylglycerols stored in adipose tissue is catalyzed by the enzyme _______.
hormone-sensitive lipase
which of the following lipoprotein particles has the greatest relative content (percent weight) of proteins?
a) CM
b) VLDL
c) LDL
d) HDL
d) HDL
what are the B-oxidation products of stearic acid, a saturated fatty acid with 18 carbons?
8 NADH, 8 QH2, 9 acetyl-CoA
the substrate for each round of B oxidation is _______.
acetyl-CoA
what transport system moves activated fatty acids from the cytosol to the mitochondrial matrix?
a) tracylglycerol shuttle
b) glycerol phosphate shuttle
c) acyl adenylate shuttle
d) lipoprotein shuttle
e) carnitine shuttle
e) carnitine shuttle
the products of each round of B oxidation include _______ and ______.
NADH and QH2
during B-oxidation of an odd-chain fatty acid, the last three carbon atoms from the oxidized fatty acid enter the citric acid cycle as ________.
a) propionyl-CoA
b) methylmalonyl-CoA
c) succinyl-CoA
d) succinate
e) fumarate
c) succinyl-CoA
