Exam 3 Questions
What type of transporter is the sodium-glucose transporter? Entry field with correct answer A primary antiporter. A secondary antiporter. A primary symporter. A secondary uniporter. A secondary symporter.
A secondary symporter.
A pore that simultaneously transports two different molecules in different directions is called Entry field with correct answer a gap junction. a symport. a uniport. an equilibrium channel. an antiport.
an antiport.
Which of the following is not an example of a passive-mediated transporter? Entry field with correct answer aquaporins the Kv ion channel GLUT1 lactose permease none of the above
lactose permease
Proteins that bind to specific carbohydrates are called ______. Entry field with correct answer pectins oligonucleotides glycosaminoglycans lectins chitins
lectins
Which of the following channels open in response to an extracellular stimulus such as a neurotransmitter? Entry field with correct answer mechanoselective channels ligand-gated channels signal-gated channels voltage-gated channels All of these are sensitive to an extracellular stimulus..
ligand-gated channels
Which of these is not an artificial sweetener? Entry field with correct answer saccharine aspartame maltose acesulfame alitame
maltose
Which of the following is a disaccharide? Entry field with correct answer amylose saccharin aspartame amylopectin none of the above
none of the above
Bacterial cell walls are composed of _____. Entry field with correct answer pectin chondroitin sulfate chains peptidoglycans heparin proteoglycans
peptidoglycans
Which of the following is not derived from a carbohydrate? Entry field with correct answer Hyaluronic acid Muramic acid Stearic acid Aldonic acid
Stearic acid
The rapid transport of K+ ions by the KcsA ion channel moves up to ____ ions per ______. Entry field with correct answer 108; second 108; hour 106; minute 1023; minute 101; second
108; second
D-fructose has 3 asymmetric carbon atoms. How many epimers does it have in the D-configuration. Entry field with correct answer 6 2 3 0
2
The following are steps which incompletely describe the mechanism by which Na+ and K+ ions are transported by the (Na+—K+)—ATPase. What is the correct sequence for the events listed, assuming that K+ ions have just dissociated? 1. The phosphate group on the protein is hydrolyzed. 2. ATP binds to the protein. 3. The protein's conformation changes, exposing K+ binding sites to the cell interior. 4. Na+ ions dissociate.
2, 4, 1, 3
D-glucose has 4 asymmetric carbon atoms. How many epimers does it have in the D-configuration? Entry field with correct answer 3 8 0 4
3
How many stereoisomers are possible for a ketopentose such as ribulose? Entry field with correct answer 2 4 8 16 32
4
How many stereoisomers are possible for an aldopentose such as ribose? Entry field with correct answer 2 4 8 16 32
8
Which of the following statements most accurately defines the term "antiport?" Entry field with correct answer A protein which transports two substances in the same direction up their concentation gradients. A protein which transports two substances in opposite directions. A protein which transports two substances in the same direction. A protein which transports two substances in opposite directions up their concentation gradients.
A protein which transports two substances in opposite directions.
Which of the following statements most accurately defines the term "symport?" Entry field with correct answer A protein which transports two substances in opposite directions. A protein which transports two substances in the same direction up their concentation gradients. A protein which transports two substances in opposite directions up their concentation gradients. A protein which transports two substances in the same direction.
A protein which transports two substances in the same direction.
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: Entry field with correct answer A. Glu and Asp residues. B. Lys and Arg residues. C. Ser and Thr residues. D. Gln and Asn residues. Both C and D are correct.
A. Glu and Asp residues.
Which of the following statements correctly distinguishes transporters (carrier proteins) from porins and ion channels? Entry field with correct answer A. Transporters exhibit a conformational change when substrate binds but porins and ion channels do not. B. Porins and ion channels have a 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. Both A and B are correct. All of the above are correct.
All of the above are correct.
D-glucose is added to cells and the rate of glucose transport is plotted against D-glucose concentration. In the presence of the D-galactose derivative 6-O-benzyl-D-galactose, the curve is shifted to the right, indicating that D-glucose and the D-galactose derivative both compete for a place in the binding site. Which of the following is true? Entry field with correct answer The D-galactose derivative occupies some of the available binding sites. Given the same concentration of glucose available, the number of binding sites with D-glucose present would decrease. Given the same concentration of glucose, the rate of D-glucose flux would remain the same with the D-galactose derivative added. Presumably a higher concentration of D-glucose would be required in order to maintain the same rate of D-glucose flux as before the D-galactose derivative was added. All of the above are true.
All of the above are true.
Which of the following statements applies to all artificial sweeteners? Entry field with correct answer Artificial sweeteners cannot be readily metabolized. Artificial sweeteners are peptides and provide important amino acids. Artificial sweeteners have fewer calories than sucrose. Artificial sweeteners are much sweeter than sucrose. All of the above.
Artificial sweeteners are much sweeter than sucrose.
N-linked oligosaccharides can be covalently linked to proteins at which amino acid? Entry field with correct answer Gly Ser Glu Tyr Asn
Asn
Which of the following sequences represents a recognition site for N-linked glycosylation where X is any amino acid except Pro? Entry field with correct answer Gln—X—Ser His—X—Ser Arg—X—Ser Asn—X—Ser Asp—X—Ser
Asn—X—Ser
Which is not a structural component of peptidoglycan? Entry field with correct answer Pentaglycine Disaccharide Tetrapeptide Sulfate
Sulfate
Which bond is not considered a glycosidic bond? Entry field with correct answer Between an anomeric carbon and an alcohol oxygen. Between an anomeric carbon and the nitogen of acetylamine. Between the oxygen of one anomeric carbon and the carbon of another anomeric carbon. Between the oxygen of carbon 3 of ribose and a phosphate.
Between the oxygen of carbon 3 of ribose and a phosphate.
In terms of structure, what is the main difference between a-amylose and amylopectin? Entry field with correct answer a-amylose is a linear polymer with -(1->6) glycosidic linkages, but amylopectin has -(1->4) glycosidic linkages. -amylose is a linear polymer with -(1->4) glycosidic linkages, but amylopectin ias a linear polymer of -(1->6) glycosidic linkages. -Amylose has only one reducing end. Both contain a-(1->4) glycosidic linkages of D-glucose, but amylopectin also has a-(1->6) branches.
Both contain a-(1->4) glycosidic linkages of D-glucose, but amylopectin also has a-(1->6) branches.
Which of the following does not accurately describe glycosylation sites of proteins? Entry field with correct answer In loops or turns Asn, Ser, or Thr residues Buried residues inside proteins On the surfaces of proteins
Buried residues inside proteins
Which of the transporters listed below differs from the others? Entry field with correct answer (Na+-K+)-ATPase Na+-glucose transporter Ca2+-ATPase lactose permease KcsA
KcsA
D-Allose is an aldohexose. Methylation of which hydroxyl group on B-D-allopyranose prevents the molecule from mutarotating to a-D-allopyranose? Entry field with incorrect answer C1 C2 C3 C4 C5
C1
In terms of structure, which of the following is the main difference between cellulose and chitin? Entry field with correct answer Cellulose is neutral, but chitin is negatively charged. Cellulose is linear, but chitin is branched. Cellulose is a linear polymer of D-glucose, but chitin is a linear polymer of N-acetyl-D-glucosamine. Cellulose is formed by β-(1->4) glycosidic bonds, while chitin is formed by a-(1->4) glycosidic bonds
Cellulose is a linear polymer of D-glucose, but chitin is a linear polymer of N-acetyl-D-glucosamine.
In terms of structure, what is the main difference between -amylose and cellulose? Entry field with correct answer Cellulose is linear, but a-amylose is branched. Cellulose is formed by β-(1->4) glycosidic bonds, but α-amylose is formed by a-(1->4) glycosidic bonds. Cellulose is branched, but a-amylose is a linear polymer. Cellulose is a linear polymer of D-glucose, but a-amylose is a linear polymer of D-allose.
Cellulose is formed by β-(1->4) glycosidic bonds, but α-amylose is formed by a-(1->4) glycosidic bonds.
Which of the following statements is true regarding ion channels? Entry field with correct answer Protein structure studies indicate a flexible pore size capable of transporting ions of varying size. Ions require waters of hydration for sufficient passage through the entire channel. Ion channels maintain sodium and potassium ion concentrations that are greater in the extracellular fluid than in the cytosol. Channel rigidity minimizes energy states for appropriately sized ions. None of the above is true regarding ion channels.
Channel rigidity minimizes energy states for appropriately sized ions.
D-Glucose and D-mannitol are similarly soluble, but D-glucose is transported through the erythrocyte membrane four times as rapidly as D-mannitol. What is the most likely explanation? Entry field with correct answer D-glucose undergoes simple diffusion more rapidly than mannitol because glucose is less polar. D-glucose and D-mannitol enter the erythrocyte via an ion-gated channel. D-glucose and D-mannitol are transported via a system that distinguishes the two sugars. D-glucose flux through the membrane is linear whereas D-mannitol flux is described by a hyperbolic curve. None of the above provides the explanation
D-glucose and D-mannitol are transported via a system that distinguishes the two sugars.
Which feature of the bacterial peptidoglycan is not essential for its structural stability? Entry field with correct answer D-monosaccharides. D-amino acids. N-acetylmuramic acid. L-amino acids such as lysine.
D-monosaccharides.
Which of the following tests cannot be used to distinguish between mediated and non-mediated transport? Entry field with correct answer Determine the dependence of the concentration of the substance on its rate of transport. Determine the rate of transport at various temperatures. Determine if the transport can be blocked by reagents that chemically modify proteins. Determine if the presence of a similar substance is inhibitory.
Determine the rate of transport at various temperatures.
Valinomycin, a substance which transports K+ ions across lipid bilayers and down their concentation gradient, kills cells. Which of the following is the cause of cell death? The (Na+—K+)—ATPase cannot work in the absence of a K+ ion concentration gradient. Elevated concentrations of K+ ions inside a cell are toxic. A K+ ion concentration gradient is essential for secondary active transport. Dissipating the K+ ion concentration gradient results in uncontrolled ATP hydrolysis.
Dissipating the K+ ion concentration gradient results in uncontrolled ATP hydrolysis.
Which statement about stereoisomers is false? Entry field with correct answer Anomers freely interconvert in solution through a linear intermediate. Some hexoses can interconvert between pyranose and furanose forms. D- and L-isomers are mirror images of each other. Epimers can interconvert rapidly in solution.
Epimers can interconvert rapidly in solution.
Which of the following methods will allow you to determine if a substance used mediated transport? Entry field with correct answer Measure the rate of transport to determine if it is high or low relative to other transport systems. Evaluate the flux at several different concentrations of the substance and look for hyperbolic dependence. Monitor transport rates at a variety of concentrations and confirm a linear dependence. Compare rate of transport in an in vitro system to those in vivo. None of the above.
Evaluate the flux at several different concentrations of the substance and look for hyperbolic dependence.
The E. coli maltoporin utilizes what has been termed the greasy slide. Which of the following statements best describe the function of the greasy slide? Entry field with correct answer There is a pathway of phospholipids that line the inside of the channel and facilitate transport. A series of aromatic side chains arrange in a helical pattern matching the relative curvature of the protein backbone, thus provided little restriction to transport. Constriction in the channel removes waters of hydration, thus making the substrate more hydrophobic and "greasy." Hydroxyl groups on glucose hydrogen bond with polar and charged side chains lining the channel, thus resulting in a series of interactions mimicking a screw-like pathway. Amino acids side chains lining the channel are small and non-bulky, making steric constriction essentially non-existent.
Hydroxyl groups on glucose hydrogen bond with polar and charged side chains lining the channel, thus resulting in a series of interactions mimicking a screw-like pathway.
Gated ion channels I. exist because active transporters cannot maintain the gradient at a rate equal to non-gated ion flow. II. remain open unless acted on by an external stimulus. III. remain open to all ions that are smaller than the pore diameter. IV. can transport varying ions.
I
ClC Cl- channels I. assist in transport by forming a strong electrical dipole with the N-terminal end positively charged. II. effectively funnel ions into the pore via electrostatic interactions with basic amino acids. III. have a selectivity filter constructed from the N-terminal ends of -helices, whose dipoles attract Cl- ions. IV. rely on the side chain hydroxyl groups from Ser and Tyr.
I, II, III, IV
Which of the following correctly rank the steps in erythrocyte glucose transport by GLUT1? I. Glucose binding results in a conformational change, opening the binding site on the opposite side of the membrane II. Glucose binds to the transporter on one side of the membrane III. The transporter reverts to initial conformation IV. The glucose disassociates
II, I, IV, III
Which features allow the KcsA channel to selectively transport K+? I. The entrance of the channel contains hydrophobic residues which forces the removal of waters of hydration. II. It is attracted to the entrance of the channel via electrostatic interactions. III. The "selectivity filter" involves a narrowing of the channel, allowing only dehydrated K+ access. IV. As K+ is transported through the channel it interacts with −C=O groups from the protein.
II, III, IV
Which of the following is (are) characteristic of the (Na+-K+)-ATPase? I. It binds Na+ and K+ simultaneously prior to binding ATP II. It is covalently modified by phosphorylation at an Asp residue when Na+ is present. III. Transport of Na+ and K+ occur in a 1:1 ratio, thus maintaining a balanced gradient until opening of the gated portion of the channel. IV. It is essential for excitation of nerve cells.
II, IV
Which statement about the ABO blood group antigens is false? Entry field with correct answer These antigens differ because of the activity of a specific glycotransferase. Individuals of Type A blood have both the A antigen and anti-A antibodies. These antigens occur at the nonreducing ends of the oligosaccharide component of glycolipids. Individuals of Type O blood have the H antigen and both anti-A and anti-B antibodies.
Individuals of Type A blood have both the A antigen and anti-A antibodies.
Which of the following statements about ion channels is FALSE? Entry field with correct answer Ion channels are integral membrane proteins. Ion channels allow ions to move against their concentration gradient. Ion channels are multi-subunit proteins. The selectivity of an ion channel is dependent upon the amino acids that comprise the mouth of the channel.
Ion channels allow ions to move against their concentration gradient.
Which of the following statements about ion channels is FALSE? Entry field with correct answer Ion channels are multi-subunit proteins. Ion channels allow ions to move against their concentration gradient. The selectivity of an ion channel is dependent upon the amino acids that comprise the mouth of the channel. Ion channels are integral membrane proteins.
Ion channels allow ions to move against their concentration gradient.
What will happen to a solution of pure a-D-glucopyranose? Entry field with correct answer It will remain in solution, as is. It will convert completely to the more stable anomer, B-D-glucopyranose. It will convert completely to the linear form. It will begin converting to the B-anomer, eventually reaching an equilibrium concentration of 63.6 %.
It will begin converting to the B-anomer, eventually reaching an equilibrium concentration of 63.6 %.
Which of the following is evidence for aquaporins? Entry field with correct answer Kidney cells are otherwise incapable of maintaining a gradient. Kidney cell transport of water molecules can be inhibited by mercuric ions. Water, a polar substance, cannot cross the hydrophobic membrane without mediation. Rapid rates of water transport require mediation. Studies measuring flux of water molecules in the kidney yielded only linear plots of flux vs. [H2O] despite the large excess in water.
Kidney cell transport of water molecules can be inhibited by mercuric ions.
Which does not occur when neurons are stimulated? Entry field with correct answer Local depolarization results from the opening of Na+ ion channels allowing Na+ to exit the cell. Neighboring Na+ ion channels open in response to the change in membrane potential, resulting in a wave of depolarization. Depolarization stimulates the opening of ion-gated K+ channels, resulting in repolarization. Recovery involves the movement of Na+ out of the cell and K+ into the cell, resulting in the membrane regaining its resting potential. All of the above do occur when neuron are stimulated.
Local depolarization results from the opening of Na+ ion channels allowing Na+ to exit the cell.
Which one of the following steps found in N-linked glycosylation is also part of O-linked glycosylation? Entry field with correct answer A 3-residue sequence pattern in the protein determines the sites of glycosylation. Some of the sugars are removed during processing. Monosaccharides are added while the protein is in the Golgi apparatus. A 14-unit oligosaccharide is attached to the protein.
Monosaccharides are added while the protein is in the Golgi apparatus.
Which statement about N-linked glycosylation is correct? Entry field with correct answer N-linked oligosaccharides are attached to proteins one sugar at the time in the endoplasmic reticulum. N-linked sugars are attached to proteins as a 14 residue oligosaccharide during translation in the endoplasmic reticulum. N-linked sugars are attached to proteins as a 14 residue oligosaccharide during translation in the cytoplasm. N-linked sugars are attached to proteins as a 14 residue oligosaccharide after translation in the Golgi apparatus. N-linked oligosaccharides are attached to proteins one sugar at the time in the Golgi apparatus.
N-linked sugars are attached to proteins as a 14 residue oligosaccharide during translation in the endoplasmic reticulum.
f the (Na+—K+)—ATPase transporter were modified so that it could no longer be phosphorylated, which of the following would happen? Entry field with correct answer Ions would be transported down their concentration gradient. No ions would be transported. K+ ions but not Na+ ions would be transported. Na+ ions but not K+ ions would be transported.
No ions would be transported.
Which of the following is a reducing sugar? Entry field with correct answer O-D-galactopyranosyl-(1->4)-D-glucopyranose O-a-D-glucopyranosyl-(1->2)-β-D-fructofuranoside Methyl-β-D-glucopyranoside Methyl--D-glucopyranoside
O-D-galactopyranosyl-(1->4)-D-glucopyranose
The (Na+—K+)—ATPase works through changes in conformation. Which of the following mechanisms is responsible for these changes in conformation? Entry field with correct answer Allostery Phosphorylation Induced fit Cooperativity
Phosphorylation
Which of the following is not a central role of carbohydrates? Entry field with correct answer Recognition of cells and Proteins. Photoreceptors. Energy source. Structural material.
Photoreceptors.
You have discovered a protein that transports Ca2+ ions up a concentration gradient, from the cytoplasm into the endoplasmic reticulum. No other ions move during this transport. Which type of transport protein does this appear to be? Entry field with correct answer Primary active uniport. Ca2+ ion channel. Secondary active uniport. Ca2+ ion porin.
Primary active uniport.
At equilibrium in solution, D-glucose consists of a mixture of its anomers. Which statement most accurately describes this solution? Entry field with correct answer The solution consists of approximately equal amounts of the a- and B-anomers. The straight-chain form is present in high concentration. The a-anomer is more stable and is slightly preferred over the B-anomer. The B-anomer predominates over the a-anomer by a ratio of approximately 2:1. None of the answers above is correct.
The B-anomer predominates over the a-anomer by a ratio of approximately 2:1.
Transport of digested glucose across intestinal cells from the intestinal space to the blood requires multiple transporters. Which one of the following is NOT required? Entry field with correct answer The Na+—glucose symporter. The (Na+—K+)—ATPase antiporter. The K+ channel uniporter. The glucose uniporter.
The K+ channel uniporter.
Transport of digested glucose across intestinal cells from the intestinal space to the blood requires multiple transporters. Which one of the following is NOT required? Entry field with correct answer The glucose uniporter. The Na+—glucose symporter. The K+ channel uniporter. The (Na+—K+)—ATPase antiporter.
The K+ channel uniporter.
Which of the following correctly describes the reason for the specificity of valinomycin? Entry field with correct answer The K+ ion is the only ion small enough to fit through the ion channel. The K+ radius is the ideal size for a large binding affinity because it minimizes steric strain and potential for degrees of rotation. It selectively binds to the entrance of the transporter which is lined with negatively charged amino acids. All of the above describe the specificity. None of the above describe the specificity.
The K+ radius is the ideal size for a large binding affinity because it minimizes steric strain and potential for degrees of rotation.
Which of the following determines the force that "drives" an ion through an ion channel in a membrane? Entry field with correct answer The properties of the selectivity filter. The size and shape of the channel. The concentration gradient across the membrane. The size of the ion.
The concentration gradient across the membrane.
Which of the following determines the force that "drives" an ion through an ion channel in a membrane? Entry field with correct answer The properties of the selectivity filter. The size and shape of the channel. The size of the ion. The concentration gradient across the membrane.
The concentration gradient across the membrane.
Which of the following is not part of the systematic naming of an oligosaccharide? Entry field with correct answer The enzymes necessary for synthesis of the oligosaccharide. A description of the linkage between monosaccharides. The identity of each monosaccharide. The anomeric configuration of each monosaccharide.
The enzymes necessary for synthesis of the oligosaccharide.
Why does secondary active transport require the absence of porins in the membrane? Entry field with correct answer Porins are passive transporter proteins. The porins will interfere with ATP hydrolysis. The porins will interfere with ATP hydrolysis and will dissipate any ionic concentration gradients. The porins will dissipate any ionic concentration gradients. Porins are passive transporter proteins that will interfere with ATP hydrolysis and will dissipate any ionic concentration gradients.
The porins will dissipate any ionic concentration gradients.
Ion channels are selective whereas porins are not. Which of the following statements explains this difference? Entry field with correct answer In porins the channel is located within a single subunit, whereas in ion channels it is located between subunits. Porins typically cross the lipid bilayer as -barrels, whereas the subunits in ion channels cross the lipid bilayer as -helices. Ion channels transport charged substances, whereas porins transport polar substances. The quarternary structure of ion channels includes amino acid side chains that are positioned to form non-covalent interactions with the ion.
The quarternary structure of ion channels includes amino acid side chains that are positioned to form non-covalent interactions with the ion.
Which of the following statements about glycosaminoglycans is strictly true? Entry field with correct answer They have repeating units of disaccharides. They are made from modified galactose monosaccharides. They are highly hydrated, negatively charged linear polymers. They contain one or more sulfate groups per disaccharide.
They are highly hydrated, negatively charged linear polymers.
Which of the following statements about passive transporter proteins and ion channels is FALSE? Entry field with correct answer They both change conformation during the transport process. They are both integral membrane proteins. They both show a high degree of selectivity. They both transport substances down a concentration gradient.
They both change conformation during the transport process.
In which way are saccharides similar to amino acids? Entry field with correct answer Their polymers are not made from a template. They do not form polymers capable of catalysis. They are formed from three elements, C, H, and O. They can be joined covalently to form polymers.
They can be joined covalently to form polymers.
Which of the following statements is FALSE with respect to secondary active transporters? Entry field with correct answer Transport occurs via integral membrane proteins which change their conformation. They require free energy input to pump a substance against its concentration gradient. They catalyze ATP hydrolysis to pump a substance against its concentration gradient. They couple the transport of one substance against its concentration gradient with cotransport of a second substance down its concentration gradient.
They catalyze ATP hydrolysis to pump a substance against its concentration gradient.
Which of the following is NOT a feature of active transport processes? Entry field with correct answer They occur via proteins that form a channel through the membrane. They require input of free energy. They occur via proteins that are classified as uniport, symport, or antiport. They are highly specific with respect to substrate.
They occur via proteins that form a channel through the membrane.
Which of the following is TRUE for BOTH primary and secondary active transporters? Entry field with correct answer They require free energy input to move a substance against its concentration gradient. They couple the transport of one substance against its gradient with cotransport of a second substance down its concentration gradient. Transport occurs via proteins that form a channel through the membrane. They catalyze ATP hydrolysis to pump a substance against its concentration gradient.
They require free energy input to move a substance against its concentration gradient.
Which statement about aquaporins is false? Entry field with correct answer They transport water and hydronium ions efficiently. They exclusively transport water molecules at a high rate. They use hydrogen bonding to side chain NH2 groups of two Asn residues to exclude proton transport within the pore. They have a narrow constriction approximately equal to the van der Waals diameter of a water molecule. They use Arg and His side chains to remove associated water molecules from the 'transported' H2O.
They transport water and hydronium ions efficiently
Which statement does not describe the transport of ions by valinomycin? Entry field with correct answer Mutations in the peptide sequence may alter ability to transport through the membrane. Transport may be active or passive. The active site binds K+ with greater affinity than Na+ Transport results in equilibration of a concentration gradient across membranes. All of the above do describe transport by valinomycin.
Transport may be active or passive.
Cellulose is Entry field with correct answer a linear copolymer of glucose and galactose. a branched polymer of glucose. a linear polymer of glucose with β(1->4) linkages. a linear polymer of glucose with a(1->4) linkages. sometimes called starch.
a linear polymer of glucose with β(1->4) linkages.
The Kv channel is transiently closed by ___________. Entry field with correct answer a spherical globular segment on the N-terminus a C-terminal segment activated by proteolysis proteoglycan residues an ion larger than the selectivity filter blocking entry tightly-bound Ca2+
a spherical globular segment on the N-terminus
Which polysaccharide is found in a helically coiled conformation? Entry field with correct answer chitin a-amylose cellulose lignin none of the above
a-amylose
Starch is a mixture of Entry field with correct answer a-amylose and amylopectin. glycogen and amylopectin. glycogen and a-amylose. glycogen and cellulose. a-amylose and maltose.
a-amylose and amylopectin.
Which of the following terms does NOT describe a transport process with a negative free energy change for the transported molecule? Entry field with correct answer spontaneous active downhill favourable exergonic
active
Gap junctions Entry field with incorrect answer connect the cytoplasm to the extracellular solution thus allowing transfer of small molecules out of the cell into the extracellular solution. are essential communication channels between the cell and the extracellular solution. allow exchange of small molecules between cells within an organ. allow intercellular exchange of macromolecules. All of the above.
allow exchange of small molecules between cells within an organ.
Which of these polysaccharides is a branched polymer? Entry field with correct answer chitin amylose cellulose amylopectin hyaluronic acid
amylopectin
The transformation of a monosaccharide into its ______ occurs easily and does not require the assistance of a catalyst. Entry field with correct answer epimer anomer sugar alcohol diastereomer none of the above
anomer
The sialic acids Entry field with correct answer are important constituents of glycoproteins and glycolipids. are N-acetyl glucosamine derivatives. incorporate a succinic acid derivative. all of the above none of the above
are important constituents of glycoproteins and glycolipids.
Which of the following polysaccharides cannot be digested by mammalian salivary, gastric, or pancreatic enzymes? Entry field with correct answer cellulose amylopectin amylose glycogen starch
cellulose
Glycoproteins Entry field with correct answer are only found in bacteria. are extremely homogeneous. are typically less than 1% carbohydrate by weight. are assembled under strict genetic control. exhibit microheterogeneity.
exhibit microheterogeneity.
The bonding of alcohols to the anomeric center of a carbohydrate results in the formation of a(n) __________ bond. Entry field with correct answer anomeric amide glycosidic ester hydrogen
glycosidic
Alcohols react with aldehydes to form Entry field with correct answer hemiketals. lactones. lactams. glycosides. hemiacetals.
hemiacetals.
Which of the following compounds would cross a biological membrane most readily by nonmediated diffusion? Entry field with correct answer hexane methanol water acetone acetic acid
hexane
Which of the following is an example of a heteropolysaccharide? Entry field with correct answer cellulose chitin starch glycogen hyaluronic acid
hyaluronic acid
A graph of the rate of glucose transport via the GLUT1 transporter vs. glucose concentration would have a ________ shape indicating that higher glucose concentrations increase the rate of transport until all the sites are saturated. Entry field with correct answer linear bell sigmoidal exponential hyperbolic
hyperbolic
Valinomycin Entry field with correct answer is a cyclic polypeptide that functions as a K+ carrier. is a transmembrane polypeptide that transports K+. is a cyclic polypeptide that functions as a Na+ carrier. is a transmembrane polypeptide that transports Na+. is a -barrel pore transporter that transfers K+.
is a cyclic polypeptide that functions as a K+ carrier.
A saccharide that has free aldehyde group is called a(n) _____________. Entry field with correct answer ketose nonreducing sugar reducing sugar aldohexose alditol
reducing sugar
Chitin differs from cellulose due to Entry field with correct answer inversion of configuration at the anomeric carbon. sulfonation of the C2—OH group. a much greater prevalence of branching. replacement of the C2—OH group by an acetamido group. replacement of the C6—OH group by an amino group.
replacement of the C2—OH group by an acetamido group.
Which of the following is an example of nonmediated transport? Entry field with correct answer simple diffusion facilitated diffusion passive transport active transport all of the above
simple diffusion
Which of the following is a mixture of two types of polymers? Entry field with correct answer cellulose starch chitin glycogen amylose
starch
Which of the following is the most abundant disaccharide? Entry field with correct answer lactose cellulose -amylose maltose sucrose
sucrose
Which of the following sugars is not a reducing sugar? Entry field with correct answer glucose ribose sucrose starch galactose
sucrose
The greater the magnitude of the concentration gradient: Entry field with correct answer the more rapid the rate of diffusion. the more likely mediated transport is required. the easier it is to reverse the flux. the higher number of ATPs required to diffuse. All of the above are true.
the more rapid the rate of diffusion.
O-linked oligosaccharides are commonly attached to the —OH group of _____. Entry field with correct answer ribose tyrosine lysine threonine glycine
threonine
Of the transport proteins discussed in the chapter, in general, which of the following do they have in common? Entry field with correct answer move in the direction of the gradient require hydrophobic amino acid side chains to line the pores utilize stereospecifcity to selectively transport transport ionized substances utilize conformational changes to control flux
utilize conformational changes to control flux