MCAT Question of the Day 301-400 I Research Analysis Questions
Part 4: (Questions 301-400)
Question 301: What is the isoelectric point of histidine?
A. 7.6
B. 3.91
C. 5.5
D. 5.7
Question 302: How would you go about calculating the isoelectric point, based on the information presented in the titration curve above?
A. Add 6.0 to 9.17, then divide by two.
B. Add 6.0 to 1.82, then divide by two.
C. Add 1.82 to 9.17, then divide by two.
D. Add 1.82, 6.0, 9.17, then divide by two.
Question 303: The pKa’s for valine are 2.2 and 9.6. The pKa’s for phenylalanine are 1.8 and 9.2. The pKa’s for tyrosine are 2.0, 10.5 and 9.4. The pKa’s for proline are 2.0 and 10.6. The pKa’s for arginine are 1.8, 9.0 and 12.5. The net charge on the peptide Tyr-Arg-Pro-Phe at pH 1.8 is:
A. +0.5
B. +1.0
C. -0.5
D. +1.5
Question 304: Which values in the problem above can be ignored, before even considering the question?
A. Tyrosines’s N-value (9.4), all of proline’s values (2.0/10.6), arginine’s N & C values (1.8/9), all of Valine’s values (2.2/9.6), and Phenylalanine’s N-value.
B. Tyrosines’s R-value (9.4), all of proline’s values (2.0/10.6), arginine’s N & C values (1.8/12.5), and Phenylalanine’s N-value.
C. Tyrosines’s C-value (2.0), all of proline’s values (2.0/10.6), arginine’s N & C values (1.8/12.5), and Phenylalanine’s N-value.
D. None of the values can be ignored.
Question 305: The pKa’s for valine are 2.2 and 9.6. The pKa’s for phenylalanine are 1.8 and 9.2. The pKa’s for proline are 2.0 and 10.6. The pKa’s for arginine are 1.8, 9.0 and 12.6. The isoelectric point of the peptide Arg-Pro-Phe is:
A. 9.8
B. 11.6
C. 5.4
D. 10.8
Question 306: Which values in the problem above can be ignored, before even considering the question?
A. All of proline’s values (2.0/10.6), arginine’s N & C-values (1.8/12.5), and Phenylalanine’s N-value.
B. Proline’s N-value (10.6), arginine’s N & C-values (1.8/12.5), and Phenylalanine’s N-value.
C. All of proline’s values (2.0/10.6), arginine’s C-value (1.8), and Phenylalanine’s N-value.
D. None of the values can be ignored.
Question 307: Which of the following steps should you take in solving problem 305?
A. Align the peptide fragments in their order. Add the N- group of proline (10.6) to the N-terminus of the peptide (9.0) because they closest to each other spatially, and then divide by 2.
B. Align the peptide fragments in their order. Add the N group of proline (10.6) to the R-group of arginine (12.6) because they are most similar in number, and then divide by 2.
C. Align the peptide fragments in their order. Add the C-terminus of the peptide (1.8) to the N-terminus of the peptide (9.0) because this accounts for the entirety of the peptides charge, and then divide by 2.
D. Align the peptide fragments in their order. Add the R group of arginine to the N-terminus of the peptide because they are most similar chargeable groups, and then divide by 2.
Question 308: Which of the following statements is true?
A. The side chains of glutamine and glutamate have very similar pKa values
B. The side chains of serine and cysteine have very similar pKa values
C. The side chains of lysine and arginine have very similar pKa values
D. The unprotonated form of lysine’s side chain is a weaker base than the unprotonated form of arginine’s side chain.
Question 309: Which of the following is the weakest base?
A. The side chain guanidine group of arginine.
B. The carboxylate anion in the side chain of aspartate.
C. The imidazole group in the side chain of histidine.
D. The carboxylate anion at C1 of alanine.
Question 310: Which of the following groups of three amino acids contain only amino acids with non-polar side chains?
A. Proline, methionine, valine.
B. Leucine, lysine, isoleucine.
C. Glycine, glutamine, methionine.
D. Tryptophan, tyrosine, phenylalanine.
Question 311: Which of the bonds in the picture above are peptide bonds?
A. 1 & 2
B. 1, 2 & 3
C. 3 only
D. 4 only
Question 312: Which of the bonds in the picture above have double bond character?
A. 1 & 2
B. 1, 2 & 3
C. 3 only
D. 4 only
Question 313: The dipeptide in the picture above is in which of the following conformations?
A. Cis
B. Trans
C. Saturated
D. Not listed
Question 314: What amino acids make up the dipeptide above?
A. Alanine & Cysteine
B. Alanine & Glutamine
C. Methionine & Glutamate
D. Valine & Proline
Question 315: The amino acids in the dipeptide above to which group(s)?
A. Nonpolar
B. Polar charged
C. Polar uncharged
D. Both A & C.
Question 316: Which of the following statements about protein structures is true?
A. Once a protein has been denatured, it can never be properly refolded.
B. Urea {(NH2)2C=O}is a commonly utilized denaturing reagent, useful because of its ability to bind to hydrophobic regions of proteins.
C. The re-formation of a disulfide bond, from two cysteine residues, that has been previously cleaved by the addition of 2-mercaptoethanol, involves a 2-electron reduction of the cysteine thiol groups.
D. In hydrogen bond stabilized “reverse turns” (also called “beta bends”), the peptide bond N-H group serves as the hydrogen bond donor.
Question 317: The single most important factor responsible for the distribution of specific amino acid types inside the interiors of soluble proteins is:
A. to avoid unfavorable London dispersion forces arising from interactions with water.
B. to avoid unfavorable entropy effects which arise from the interaction of nonpolar groups with water.
C. to maximize salt bridges in the interiors of proteins.
D. to maximize hydrogen bonding between the peptide backbones of these residues and water molecules in the interiors of proteins.
Question 318: Which of the following statements about peptide bonds is true?
A. Rotation around the peptide C-N bond is energetically unfavorable.
B. Trypsin is an effective catalyst for the hydrolysis of peptide bonds to which
methionine residues have contributed the carboxyl group.
C. Peptide bonds can serve as acids at pH values near 7.0.
D. There is free rotation around the peptide C-N bond.
Question 319 Which of the following statements about the peptide bond are true?
A. The C-N bond distance is shortened through resonance hybridization.
B. The C-N bond distance is lengthened through resonance hybridization.
C. The C-O bond is shorter than expected for a double bond.
D. The cis geometry is energetically more favorable than the trans geometry for the groups attached to the peptide N and C.
Question 320: In an aqueous solution, protein conformation is determined by two major factors. One is the formation of the maximum number of hydrogen bonds. The other is the:
A. formation of the maximum number of hydrophilic interactions.
B. maximization of ionic interactions.
C. minimization of entropy by the formation of a water solvent shell around the protein.
D. placement of hydrophobic amino acid residues within the interior of the protein.
Question 321: The reaction catalyzed by ribonuclease:
A. Involves a Zn2+ ion at the catalytic site.
B. Includes a step in which the unprotonated imidazole side chain of a histidine residue removes a proton from the substrate, generating an alkoxide-like species that is an excellent leaving group.
C. Utilizes a glutamate residue at the active site to make a water molecule a better nucleophile.
D. Proceeds through a 2’,3’-cyclic phosphodiester intermediate.
Question 322: Which of the following is true about the mechanism of lysozyme?
A. The nucleophilic attack of water on a reaction intermediate is facilitated by a glutamic acid residue acting as a general acid catalyst.
B. Based on the mechanism, one would predict that increasing the length of model poly-NAG substrates from (NAG)6 to (NAG)7 to (NAG)8 would lead to little increase in the rate of the reaction.
C. The reaction catalyzed by lysozyme is endergonic.
D. The first product released by cleavage of the substrate’s scissile bond in the presence of 18O-labeled water contains 18O in its C4-OH group.
Question 323: A peptide containing 9 amino acids is cleaved by trypsin into three tripeptides, only one of which exhibits significant absorbance at 280 nm. Treatment with cyanogen bromide does not result in any cleavage of the peptide. Which of the following is the most likely sequence for this nonapeptide: (Met = methionine; Trp = tryptophan; Gly = glycine; Arg = arginine; Glu = glutamate; Lys = lysine; Leu = leucine; and Val = valine)
A. MetTrpGlyArgGluLysTrpLeuVal.
B. MetTrpArgGlyGluLysTrpLeuVal.
C. MetLeu-ArgGlyGluLys-TrpTrpVal.
D. ValLeuArgGlyGluLysTrpTrpMet.
Question 324: Which of the following statements about gel filtration chromatography is true?
A. CM-cellulose (carboxymethyl-cellulose) is a widely used stationary phase for gel filtration chromatography.
B. The shape of a protein has absolutely no effect on its chromatographic behavior during gel filtration.
C. DEAE-cellulose (diethylaminoethyl-cellulose) is a widely used stationary phase for gel filtration chromatography.
D. In general, proteins with larger molecular masses exhibit smaller elution volumes than proteins with smaller molecular masses during gel filtration chromatography.
Question 325: Which of the following statements about protein purification is true?
A. A successful step during the purification of myoglobin would decrease the ratio of the absorbance at 435 nm (the absorbance maximum for its protoheme IX prosthetic group) to the absorbance at 280 nm.
B. Affinity chromatography purification of enzymes is a technique in which the stationary phase consists of insoluble beads to which an analog of the enzyme’s substrate has been covalently attached.
C. His-tagging of proteins for purification involves genetic manipulations that add six consecutive histidine residues to a protein, followed cell lysis and ion- exchange chromatography of the lysate as the first chromatography step.
D. Electrophoresis in the presence of the detergent SDS is a purification technique that is widely used for the preparation of catalytically active enzymes.
Question 326: Which of the following statements about protein sequencing is correct?
A. During automated, repetitive Edman degradation sequencing, amino acids are identified by the chromatographic retention times of their PTH derivatives.
B. It is usually possible to sequence proteins containing approximately 100 amino acids in a single automated, repetitive Edman degradation experiment.
C. Edman degradation chemistry involves sequential modification of amino acids, starting at the C-terminus.
D. Modification of a peptide with phenylisothiocyanate affects the strength of all peptide bonds in the peptide equally.
Question 327: Which of the following statements about protein sequencing is correct?
A. Amino acids are identified during automated repetitive Edman degradation by the chromatographic retention times of the chemically unmodified amino acids.
B. It is generally possible to sequence proteins in a single automated repetitive Edman degradation run, as long as the protein does not contain more than 300 amino acids.
C. It is necessary to cleave all disulfide bonds in a peptide before the peptide can be sequenced using automated repetitive Edman degradation.
D. The reagent 2,4-dintrofluorobenzene (DNFB) is used to initiate automated repetitive Edman degradation sequencing.
Question 328: Which of the following statements about protein sequencing is correct?
A. It is possible to determine the complete sequence of a protein as long as one has obtained complete sequences for all of the fragments generated by treatment with a single cleavage reagent.
B. Translating the nucleotide sequence of the gene that encodes a protein, always gives one an accurate amino acid sequence for the mature form of a protein.
C. In modern versions of automated Edman degradation sequencing of proteins, amino acids are identified by their extremely accurate and highly reproducible retention times for elution from a hydrophobic interaction chromatography column, after being cleaved from the peptide chain and derivatized by the Edman chemistry.
D. All of tryptic peptides produced by the trypsin-catalyzed hydrolysis of proteins have either lysine or arginine at their N-terminal ends.
Question 329: Which of the following statements about protein sequencing by Edman Degradation chemistry is true?
A. N-terminal amino groups are chemically modified with phenylisothiocyanate in the initial step.
B. N-terminal amino groups are chemically modified with dansyl chloride in the initial step.
C. Amino acids are identified by the retention times of the chemically unmodified amino acids on a hydrophobic interaction column.
D. Sequencing of proteins by this technique begins at the C-terminus of the protein.
Question 330: Which of the following statements is true?
A. Treatment of a protein with 2-mercaptoethanol would be expected to change the results of a SDS-PAGE electrophoresis pattern obtained for a heterodimeric protein in which no disulfide bonds between the two subunits are present.
B. Membrane ultrafiltration can be used for concentrating protein samples but not as a technique for changing the buffer composition of a sample.
C. Gel filtration of a solution containing fetal hemoglobin will result in the separation of its alpha (α) and gamma (γ) subunits.
D. The isoelectric point of a protein will not affect the way it will migrate during SDS-PAGE (polyacrylamide gel electrophoresis in the presence of the denaturing detergent SDS).
Question 331: The pKa of oxalic acid is 4.3. In order to prepare an oxalic acid buffer solution at pH = 3.3, the ratio of oxalic acid to oxalate anion must be:
A. 1:1.
B. 100:1.
C. 1:10.
D. 10:1.
Question 332: Which of the following is true?
A. If acid HA1 has a pKa value two units less than the pKa value of acid HA2, then the acid dissociation constant (Ka) of HA1 is 100 times greater than that of HA2.
B. Adding 0.5 mol of HCl to a solution containing 1.0 mol of sodium acetate will produce a pH different from that obtained by adding 0.5 mol of NaOH to a solution containing 1.0 mol of acetic acid.
C. If acid HA1 has a pKa value two units greater than the pKa value of acid HA2, then the acid dissociation constant (Ka) of HA1 is 100 times greater than that of HA2.
D. When strong base is added to a solution containing a mixture of acids, the acid with the largest pKa loses protons first.
Question 333: Which of the following statements about water is true?
A. It is a good solvent for salts but a poor solvent for polar, uncharged molecules.
B. Water in the liquid phase consists predominantly of monomeric H2O molecules, which do not interact appreciably with other water molecules.
C. The concentration of water in pure water is approximately 55.5M.
D. The formation of a micelle from a dispersed set of amphipathic molecules has no effect on the extent of disorder of water molecules in the system.
Question 334: Which of the following is true of isoelectric points?
A. The pI of glutamic acid can be calculated by averaging the pKa values of its side-chain and its alpha-amino group.
B. Proteins are negatively charged at pH values greater than their pI.
C. Proteins are positively charged at pH values greater than their pI.
D. The pI of lysine can be calculated by averaging the pKa values of its side-chain and its C1 carboxyl group.
Question 335: Which of the following statements is true?
A. The conjugate acid of the side-chain guanidino group of arginine is a stronger acid than the conjugate acid of the side-chain carboxylate group of aspartic acid.
B. Increasing the concentration ratio of conjugate base to acid from 1:1 to 10:1 will decrease the pH of a buffer solution by 1.0 pH unit.
C. Increasing the concentration ratio of conjugate acid to base from 1:1 to 10:1 will increase the pH of a buffer solution by 1.0 pH unit.
D. In a group of weak acids, the strongest acid will be the one with the smallest pKA.
Question 336: Acetic acid has a pKa of 4.8. How many ml of 0.1 M acetic acid and 0.1 M sodium acetate are required to prepare a 1 L of 0.1 M buffer with a pH of 5.8?
A. Acetic acid=91 ml; Acetate=909 ml.
B. Acetic acid=909 ml; Acetate=91 ml.
C. Acetic acid=919 ml; Acetate=9009 ml.
D. Acetic acid=9.1 ml; Acetate=90.9 ml.
Question 337: In the example above, how many volumes of acetate must be added for each volume of acetic acid?
A. 11.
B. 10.
C. 1.
D. 100.
Question 338: With regards to the example in question 336, which of the following statements are correct?
A. The log of base over acid would be added to the pKa of acetic acid.
B. The log of acid over base would be added to the pKa of acetic acid.
C. The log of base X acid would be added to the pKa of acetic acid.
D. The log of acid X base would be added to the pKa of acetic acid.
Question 339: The pKa of acetic acid is 4.8. In order to prepare an oxalic acid buffer solution at pH = 3.8, the ratio of acid to base must be:
A. 1:1.
B. 100:1.
C. 1:10.
D. 10:1.
Question 340: Which of the values represents the pH of a .002 M solution of HCL?
A. 2.7.
B. 2.8.
C. 5.4.
D. 5.5.
Question 341: What is the pKa value for a .002 M solution of HCL?
A. 8.7.
B. -0.000869459.
C. 869459.0.
D. 0.998.
Question 342: Which of the following regions on the above molecule participate in antigen binding?
A. A only.
B. B only.
C. A & B only.
D. C only.
Question 343: Which chains make up this region?
A. Variable light chains and heavy chains.
B. Variable heavy chains only.
C. Constant light chains only.
D. Constant heavy chains only.
Question 344: Which of the following is true about hemoglobin?
A. The heme groups present in the alpha-subunits of hemoglobin are chemically different than those found in the beta-subunits.
B. Oxygenation of a heme makes the porphyrin portion of the heme less planar.
C. The heme group present in the unique subunit of fetal hemoglobin is chemically different than that found in the mature form of hemoglobin.
D. The geometry of oxygen binding in oxyhemoglobin features a bent, rather than a linear, Fe-O-O arrangement.
Question 345: Which of the following statements about oxygen, proton and CO2 movements in mammals is true?
A. The affinity of hemoglobin for O2 increases with increasing solution acidity.
B. The binding of one O2 to hemoglobin causes the uptake of approximately 0.7 H+.
C. The pH in rapidly respiring muscle tissues is usually significantly higher than is the pH in the lungs.
D. The binding of one O2 to hemoglobin causes the release-of approximately 0.7 H+.
Question 346: Which of the following statements about hemoglobin is true?
A. The hemes present in the alpha-subunits of hemoglobin are chemically different from the hemes present in the beta-subunits.
B. The fetal form of hemoglobin has a lower affinity for 2,3-bisphosphoglyceric acid (BPG) than does adult hemoglobin.
C. The number of protein bands seen after staining a polyacrylamide gel on which a sample of pure hemoglobin had been subjected to electrophoresis will differ depending on whether or not the sample had been pre-incubated, prior to electrophoresis, with 2-mercaptoethanol.
D. BPG binding to hemoglobin is stabilized largely by hydrophobic interactions.
Question 347: Which of the following statements about hemoglobin is true?
A. Oxygen binding increases the pKa of one or more groups on hemoglobin.
B. Oxyhemoglobin is a stronger acid than deoxyhemoglobin.
C. Hemoglobin has a greater affinity for oxygen at pH 7.2 than at pH 7.6.
D. Hemoglobin is more likely to encounter a lower pH in the lungs than would be the case in actively respiring tissues.
Question 348: Which of the following is true of sickle cell hemoglobin (hemoglobin S)?
A. It forms large aggregates that are held together by hydrophobic interactions.
B. The major clinical symptoms of sickle cell anemia arises from the fact that the heme prosthetic groups of hemoglobin S are bound less tightly to the protein than is the case for wild-type hemoglobin.
C. The beta subunits of wild type hemoglobin and hemoglobin S have identical electrophoretic mobilities.
D. The major clinical symptoms of sickle cell anemia arise from the fact that hemoglobin S binds BPG (2,3-bisphosphoglycerate) less tightly than does wild- type hemoglobin.
Question 349: Which of the following statements about hemoglobin is true?
A. The hemes present in the alpha-subunits of hemoglobin are chemically different from the hemes present in the beta-subunits.
B. The fetal form of hemoglobin has a lower affinity for 2,3-bisphosphoglyceric acid (BPG) than does adult hemoglobin.
C. The number of protein bands seen after staining a polyacrylamide gel on which a sample of pure hemoglobin had been subjected to electrophoresis will differ depending on whether or not the sample had been pre-incubated, prior to electrophoresis, with 2-mercaptoethanol.
D. BPG binding to hemoglobin is stabilized largely by hydrophobic interactions.
Question 350: Which of the following statements about hemoglobin is true?
A. The heme iron in hemoglobin must be in the Fe3+ ferric state to bind oxygen reversibly.
B. The binding of 2,3-bisphosphoglyceric acid (BPG) in the central cavity of hemoglobin results largely from interactions with negatively-charged side chains of the protein.
C. Oxygen binding results in the movement of the iron-binding histidine towards the heme plane.
D. Removal of BPG from hemoglobin makes oxygen binding more cooperative.
A first year graduate student with very little lab experience (due to the fact that he only participated in undergraduate research to boost his medical school application) strutted onto campus to attend his first day at the graduate school he is now attending while reapplying. As he was walking by the library, he tripped over his Crocs® and face-planted into the dirt, where a pile of ideas for two novel enzymes laid in waiting for him. He jumped to his feet, dusted off his scrubs, and immediately ran into the laboratory to gather data about his two extraordinary new proteins, named “Cut-Ting” & “Doc-Tor”.
Question 351: Which of the following represents the value for Cut-Ting’s initial reaction velocity when the concentration of substrate is equal to 3μM?
A. 78.1
B. 53.1
C. 26.9
D. 156.3
Question 352: Which of the following statements are correct regarding your computation of Question 351?
A. The use of the Michaelis-Menton equation: (VM)([s])/(KM+[S])=V0 is required.
B. The KM can be estimated by multiplying VM by 0.5, roughly charting that value right over to the point on Cut-Ting’s curve, and then down to a value that can also be estimated by using the lines on the chart.
C. Rounding decimal numbers up to make the computation achievable without use of a calculator.
D. All of the above.
Question 353: Suppose that the concentration of substrate in Question 351 was increased to 10μM. Which of the following statements reflects the effect this would have on Doc-Tor’s initial velocity?
A. There is minimal change to Doc-Tor’s KM.
B. V0 increases by 8.95.
C. V0 increases by 11.7 percent.
D. All of the above.
Question 354: Which of the following statements about enzymes that exhibit Michaelis-Menten kinetic is true?
A. Vmax is independent of the total enzyme concentration.
B. The enzyme/substrate complex is always in equilibrium with the enzyme and substrate throughout the entire time course of the catalyzed reaction.
C. The number of enzyme-bound, non-covalent intermediates that occur in the enzymatic mechanism alter the shape of v0 vs. [S] plots.
D. The concentration of the enzyme/substrate complex reaches a steady state after a short incubation period and this steady state persists for a considerable period during the time course of the reaction.
Question 355: Which of the following is true about the Michaelis-Menten model for enzyme kinetics?
A. The enzyme/substrate complex is in equilibrium with the free enzyme and substrate throughout the steady state.
B. KM is equal to the dissociation constant for the enzyme/substrate complex in all cases.
C. The Michaelis-Menten model is not applicable to reversible reactions.
D. Restricting data used to early times allows one to ignore the contributions of the reverse reaction to Michaelis-Menten analyses of reversible reactions.
Question 356: Which of the following statements is true?
A. Some allosteric effectors increase the rates of enzyme-catalyzed reactions, while others decrease the rates of enzyme-catalyzed reactions.
B. ATP is involved in feedback inhibition of the metabolic pathway for which aspartate transcarbamoylase catalyzes the first step.
C. Plots of the initial rate of the reaction catalyzed by aspartate transcarbamoylase vs. aspartate concentration are hyperbolic.
D. Feedback inhibition usually occurs at a late step in a metabolic pathway.
Question 357: Which of the following statements is true?
A. Transition states occur at minima in free energy vs. reaction coordinate diagrams.
B. Catalysts stabilize the transition states for the forward direction of exergonic reactions but do not stabilize the transition states for the reverse reactions.
C. Transition-state analogs are often highly effective inhibitors of enzyme- catalyzed reactions because they bind to the enzyme active site with much higher affinity than do the substrates.
D. The conversion of the zymogen, trypsinogen, to trypsin has no effect on the protein’s ability to stabilize a catalytically important transition state.
Question 358: Which of the following statements about competitive inhibitors is true?
A. The inhibition results from binding of the inhibitor to the enzyme/substrate complex but not to the free enzyme.
B. The inhibition produced by this class of inhibitors can be reversed by extensive dialysis.
C. These inhibitors decrease the Vmax without affecting the apparent KM.
D. These inhibitors decrease the apparent KM without affecting Vmax.
Question 359: Which of the following is true about aspartate transcarbamoylase:
A. The enzyme contains an equal number of regulatory and catalytic subunits.
B. CTP inhibits the enzyme by competing with carbamoyl phosphate for occupancy of a substrate-binding site.
C. CTP binds to the regulatory subunit while ATP binds to the catalytic subunit.
D. It is NOT possible to remove the regulatory subunits from the catalytic subunits without eliminating the catalytic ability of the catalytic subunits.
Question 360: The above pathway portrays which of the following ideas regarding metabolic flux regulation?
A. Glucose utilization is inhibited by the utilization of alternative substrates.
B. Insulin plays a lesser role in flux regulation than glucagon.
C. The inhibition of glucose utilization is reversed by cyclic AMP.
D. Both A & C.
Question 361: Which of the following hormones are related to the increased cellular concentration of cAMP acting on these glycolytic enzymes?
A. Glucagon.
B. Insulin.
C. Epinephrine.
D. Both A & C.
Question 362: Glucagon promotes which of the following?
A. Glycogen degradation.
B. Gluconeogenesis.
C. Glycogen synthesis.
D. Both A & B.
Question 363: Where does gluconeogenesis take place?
A. In the cytosol of hepatocytes.
B. In the cytosol of myocytes.
C. In the mitochondria of hepatocytes.
D. Both A & C.
Question 364: The alternative substrates mentioned in the pathway above likely have which of the following short-term effects on glucose uptake?
A. Inhibition of GLUT transport proteins.
B. Stimulation of glucose intake.
C. No effect on GLUT transport proteins.
D. No effect on glucose intake.
Question 365: Gluconeogenesis is:
A. The breakdown of glycogen into glucose.
B. The synthesis of glycogen from glucose.
C. The synthesis of glucose from non-carbohydrate intermediates.
D. The synthesis of glucose from fatty acids.
Question 366: Which of the following statements about sugars is true?
A. There are no known ketotrioses.
B. Glyceraldehyde, an aldotriose, contains no chiral carbons.
C. D-Glucose exists in solution entirely (i.e., 100%) as an intramolecular cyclic compound.
D. There are 8 different pairs of enantiomers in the family of aldohexoses.
Question 367: Which of the following statements about sugars is true?
A.
There are 16 different pairs of enantiomers in the family of aldohexoses.
B. Glucose is referred to as a “reducing sugar” because it can be oxidized by a number of Fe2+ and Cu+ reagents.
C. Glyceraldehyde, an aldotriose, contains no chiral carbons.
D. There are no known ketotrioses
Question 368: Which of the following statements about sugars is correct?
A. The ketotriose, dihydroxyacetone, exists as a pair of enantiomers.
B. The family of aldohexoses has 3 chiral centers.
C. The predominant form of D-fructose in solution is a six-membered ring.
D. D-glucose and L-glucose are enantiomers.
Question 369: Which of the following statements about sugars is true?
A. The predominant form of D-glucose in solution is a six-membered ring in the chair conformation.
B. The conversion of the open-chain form of glucose to its cyclic form does not change the number of chiral centers present in the molecule.
C. The predominant form of the aldotriose, glyceraldehyde, in solution is a four- membered ring.
D. The predominant form of D-glucose in solution is a completely planar, six- membered ring.
The figure above is an attempt to incorporate several ideas re. intermediary metabolism; and is not intended as a comprehensive listing of the reactions that take place during the listed processes. Nevertheless, please utilize it as for reference in answering Questions 370-389.
Question 370: Which of the following enzymes link glycolysis to the TCA Cycle?
A. Pyruvate kinase.
B. Pyruvate dehydrogenase.
C. Glyceraldehyde-3-Phosphate
D. Malate dehydrogenase.
Question 371: The production of NADH in the TCA cycle:
A. Inhibits enzymes in the pathway as a mechanism of feedback inhibition.
B. Enters electron transport at Complex III.
C. Can be converted into glucose.
D. Can be converted into fatty acids.
Question 372: Anaploretic reactions carried out by ____, and activated by acetyl-CoA replenish the citric acid cycle intermediates.
A. Pyruvate carboxylase.
B. Pyruvate dehydrogenase.
C. Oxaloacetate.
D. Isocitrate dehydrogenase.
Question 373: Where does the TCA Cycle take place?
A. The cytosol.
B. The mitochondria.
C. The endoplasmic reticulum.
D. In peroxisomes.
Question 374: How many NADH per glucose are reduced during the TCA Cycle?
A. 2.
B. 4.
C. 6.
D. 8.
Question 375: How many FADH2 per glucose are reduced during the TCA Cycle?
A. 2.
B. 4.
C. 6.
D. 8.
Question 376: How many ATP per glucose are directly produced during the TCA Cycle?
A. 0.
B. 2.
C. 4.
D. 6.
Question 377: Which of the following metabolic processes are not possible?
A. The synthesis of glucose from fatty acids.
B. The synthesis of glucose from amino acids.
C. The synthesis fatty acids from glucose.
D. All of the above are metabolically possible.
Question 378: Odd-chain fatty acids enter the TCA cycle at which point in the pathway?
A. They don’t.
B. Propionyl-CoA is converted to Succinyl-CoA.
C. As acetyl-CoA.
D. As Isocitrate.
Question 379: Where do even-chain fatty acids enter the TCA cycle?
A. The don’t.
B. Propionyl-CoA is converted to Succinyl-CoA.
C. As acetyl-CoA.
D. As Isocitrate.
Question 380: Which of the following is a correct descriptor with respect to oxygen’s relationship to electron transport and oxidative phosphorylation?
A. Oxygen is the terminal electron acceptor.
B. Oxygen is the penultimate electron acceptor.
C. Oxygen is not involved in either electron transport or oxidative phosphorylation.
D. Oxygen binds to ATP.
Question 381: Electrons from FADH2 enter the electron transport chain at which of the following complexes?
A. Complex I.
B. Complex II.
C. Complex III.
D. Complex IV.
Question 382: Electrons from NADH enter the electron transport chain at which of the following complexes?
A. Complex I.
B. Complex II.
C. Complex III.
D. Complex IV.
Question 383: Which of the following depicts the correct order of electron transport?
A. Complex IComplex IIComplex IIIComplex IV.
B. Complex IComplex II Complex IVComplex III.
C. Complex IComplex IIIComplex IIComplex IV.
D. This depends on whether the electrons are coming from NADH, or FADH2.
Question 384: Where does the Pentose Phosphate Pathway take place?
A. The cytosol.
B. The mitochondria.
C. The endoplasmic reticulum.
D. In peroxisomes.
Question 385: Where does electron transport take place?
A. The cytosol.
B. The mitochondria.
C. The endoplasmic reticulum.
D. In peroxisomes.
Question 386: Where does oxidative phosphorylation (ATP synthesis by ATP synthase) take place?
A. The cytosol.
B. The mitochondria.
C. The endoplasmic reticulum.
D. In peroxisomes.
Question 387: Which of the following metabolic inhibitors act on Complex 1 of the electron transport chain?
A. 2,4-Dinitrophenol.
B. Rotenone.
C. Amytal.
D. CN-
Question 388: Which of the following metabolic inhibitors act to dissipate the proton gradient?
A. 2,4-Dinitrophenol.
B. Rotenone.
C. Amytal.
D. CN-
Question 389: Where does cyanide act as a metabolic inhibitor?
A. Complex I.
B. Complex II.
C. Complex III.
D. Complex IV.
Question 390: Based on the information provided in the three graphs above, which of the following peaks represents the standard?
A. The 20ml peak.
B. The 35ml peak.
C. The 51ml peak.
D. Not enough information is provided.
Question 391: Based on the information provided in the three graphs above, which of the following peaks represents the largest protein?
A. The protein that eluted at 20ml.
B. The protein that eluted at 35ml.
C. The protein that eluted at 51ml.
D. Not enough information is provided.
Question 392: Based on the information provided in the three graphs above, which of the following peaks represents the smallest protein?
A. The protein that eluted at 20 ml.
B. The protein that eluted at 35 ml.
C. The protein that eluted at 51 ml.
D. Not enough information is provided.
Question 393: Which of the following statements is true regarding the SDS PAGE above (labeled A)?
A. The bottom of the picture represents the cathode.
B. The bottom of the picture represents the anode.
C. The largest protein is the top band.
D. The largest protein is middle protein.
Question 394: Which of the following statements is true regarding the SDS PAGE above (labeled B)?
A. The y-axis is the log of the molecular weight, and the x-axis is the distance migrated.
B. The y-axis is the molecular weight, and the x-axis is the distance migrated.
C. The y-axis is the log of the molecular weight, and the x-axis is the protein concentration.
D. Protein A is the largest protein of the five on the chart.
Question 395: Which of the following statements is true regarding the SDS PAGE above (labeled B)?
A. Protein A is the largest protein.
B. Protein B is the largest protein.
C. Proteins A, B, and C are larger than Proteins D and E.
D. Proteins A, B, and C are smaller than Proteins D and E.
Questions 396: Which of the following is true of PAGE (polyacrylamide gel electrophoresis) of proteins in the presence of SDS (sodium dodecyl sulfate)?
A. The principle role of SDS is to cleave inter-subunit disulfide bonds.
B. Proteins migrate towards the cathode during SDS-PAGE.
C. During SDS-PAGE, the relative migration distance of any one protein in a mixture of proteins is generally proportional to the log of their molecular mass.
D. The migration velocity of proteins during SDS-PAGE depends on both the molecular mass of the protein and its isoelectric point.
Question 397: Which of the following statements about gel electrophoresis is true?
A. In two-dimensional electrophoresis, it is essential to run the separation based on molecular mass before isoelectric focusing is carried out.
B. During electrophoresis of proteins in the presence of SDS, proteins with smaller molecular masses migrate more rapidly than proteins with larger molecular masses.
C. During electrophoresis of proteins in the presence of sodium dodecylsulfate (SDS), all proteins migrate towards the cathode.
D. The purpose of including a small, electrically charged dye in an electrophoresis experiment is to establish a stable pH gradient across the polyacrylamide gel.
Question 398: Addition of sodium dodecylsulfate (SDS) to a protein will:
A. Denature proteins by forming hydrogen bonds with the protein.
B. Denature proteins through hydrophobic interactions between its non-polar dodecyl group and non-polar groups on the protein.
C. Denature proteins by cleaving disulfide bonds that are essential for stabilizing the native structure.
D. Cause the protein to migrate towards the cathode during electrophoresis.
Question 399: Which of the following statements about electrophoresis is true?
A. Electrophoresis of a completely pure sample of bovine insulin in the presence of SDS plus 2-mercaptoethanol always results in a single Coomassie Blue- staining band.
B. The greatest contribution, in energetic terms, of SDS binding to proteins is the result of ion/ion interactions.
C. In a two-dimensional electrophoresis experiment, the SDS-PAGE step is done first and is then followed by the isoelectric focusing step.
D. In SDS-PAGE, all proteins migrate towards the positive electrode (i.e., the anode) when the electric field is turned on.
Question 400: Which of the following statements about gel electrophoresis is true?
A. Gel electrophoresis can be used to separate proteins but cannot be used to separate different DNA molecules.
B. The detergent sodium dodecyl sulfate, frequently used in protein
electrophoresis, is capable of cleaving peptide bonds
C. SDS-PAGE of proteins can be used both as a preparative and as an analytical technique.
D. SDS-PAGE of a sample in the absence of 2-mercaptoethanol reveals only a single band after staining with Coomassie Blue. SDS-PAGE of the same sample after pre-heating in the presence of 2-mercaptoethanol also reveals a single Coomassie Blue-staining band, but with an apparent mass half that estimated for the protein in the absence of 2-mercaptoethanol. The simplest explanation for these observations is that the sample contains a pure protein that is, in its native form, a disulfide-linked homodimer.