华中科大：生物化学双语习题：11

1. The B-DNA structure found in solution is a A????????? right-handed double helix of antiparallel chains (11 bp/turn). B????????? left-handed double helix of antiparallel chains (~10 bp/turn). C????????? right-handed double helix of antiparallel chains (~10 bp/turn). D????????? left-handed zig-zag helix of antiparallel chains (12 bp/turn). E????????? right-handed double helix of parallel chains (~10 bp/turn).
2. DNA differs from RNA in the following features A????????? DNA is resistant to base catalyzed hydrolysis; RNA is hydrolyzed by OH-. B????????? DNA residues are linked by 3'-->5' phosphodiester bonds; RNA is 2'-->5' linked. C????????? DNA has deoxyribose residues; RNA has ribose residues. D????????? DNA contains the A, C, G and T bases; RNA contains A, C, G, and U. E????????? All but the second choice are correct differences.
3. Because DNA is a highly charged polyanion, its stability to heat denaturation ("melting"): A????????? does not depend on hydrophobic interactions. B????????? increases with increasing [salt]. C????????? decreases with increasing [salt]. D????????? is independent of G + C content. E????????? increases with increasing pH.
4. The total contour length of DNA in a human cell is about A????????? 1 mm. B????????? 1 mm. C????????? 10 cm. D????????? 1 meter. E????????? 12 furlongs.
5. Polyacrylamide and agarose gel electrophoresis separate nucleic acids based primarily on their A????????? length. B????????? ratio of mass/charge. C????????? (G+C)/(A+T) content. D????????? organismal origin. E????????? content of 15N (buoyant density).
6. The number of supercoils in a covalently-closed, circular DNA can only be changed if A????????? at least one of the phosphodiester chains is cleaved. B????????? both of the phosphodiester chains are cleaved. C????????? histones are bound to the DNA. D????????? the salt concentration is increased >1.0 M. E????????? chemical reagents react with the backbone phosphates.
7. Thymidine A????????? is equal to the adenosine concentration in double-stranded DNA. B????????? is replaced by Uracil in RNA. C????????? normally forms 2 hydrogen bonds with adenosine. D????????? can participate in hydrophobic interactions due to its methyl group. E????????? All of the above are correct.
8. The major and minor grooves of B-form DNA correspond to what features of A-form RNA? A????????? minor and major grooves B????????? deep and shallow grooves C????????? deoxyribose backbones D????????? phosphoribose backbones E????????? Choices a) and d) are both correct.
9. The glycosidic bonds in DNA and RNA A????????? can be hydrolyzed by OH-. B????????? are free to rotate over about 180°. C????????? are restricted to one of four possible orientations. D????????? connect the sugar to the base. E????????? stabilize Watson-Crick H-bonds.
10. In solution, the grooves of nucleic acid helices A????????? are filled with H2O and counterions (M+ & M2+). B????????? expose the H-bonding groups of the bases. C????????? expose the hydrophobic surfaces of the bases. D????????? are about equal in width. E????????? Choices a) and b) are both correct.
11. When an aromatic molecule intercalates into the DNA double helix, the two adjacent base pairs are separated by about ______, and the helix is unwound by about _______. A????????? 3.4?, ? 36° B????????? 4.3?, ? 36° C????????? 3.4?, ? 26° D????????? 4.3?, ? 26° E????????? 1.7?, ? 10°
12. If your genomic DNA could be typed for a specific genetic defect A????????? "I would not want to be tested, ever." B????????? "I would want to be tested now." C????????? "I might want to be tested later." D????????? "I need much more information before deciding." E????????? All four decisions are now being made by reasonable people.  5 ※<2> 1. The a-amino acids have a carboxyl group with a pK around ___ , and an amino group with a pK near ___. A????????? 1, and 12.1 B????????? 6.5, and 8.0. C????????? 3, and 10.5. D????????? 9.0, and 2.5. E????????? 2.2 and 9.5.
2. Which pair of amino acids absorbs the most UV light at 280 nm? A????????? Thr & His. B????????? Trp & Tyr. C????????? Cys & Asp. D????????? Phe & Pro. E????????? None of the above.
3. Which of the following is not a sensible grouping of amino acids based on their polarity properties? A????????? Ala, Leu, and Val. B????????? Arg, His, and Lys. C????????? Phe, Trp, and Tyr. D????????? Asp, Ile, and Pro. E????????? Asn, Ser, and Thr.
4. The isoelectric point of an amino acid is defined as A????????? the pH where the molecule carries no net electric charge. B????????? the pH where the carboxyl group is uncharged. C????????? the pH where the amino group is uncharged. D????????? the pH of maximum electrolytic mobility. E????????? -log10(pKi + pKj)
5. When the amino acid alanine (the R-group is: -CH3) is added to a solution with a pH of 7.3, alanine becomes: A????????? a cation. B????????? nonpolar. C????????? a zwitterion. D????????? an isotope. E????????? an anion.
6. Aspartic acid is similar to glutamic acid in the same way that A????????? His is similar to Pro. B????????? Ser is similar to Cys. C????????? Gln is similar to Asn. D????????? Asn is similar to Gln. E????????? Gly is similar to Val.
7. Alanine is similar to serine in the same way that A????????? Val is similar to Thr. B????????? Phe is similar to Tyr. C????????? Phe is similar to Trp. D????????? Ser is similar to Thr. E????????? Trp is similar to Pro.
8. Glycine is similar to valine in the same way that A????????? Ala is similar to Leu. B????????? Thr is similar to Met. C????????? Ala is similar to Ile. D????????? Arg is similar to Lys. E????????? None of the above are valid similarities.
9. A significant difference between His and Pro is that A????????? the His side chain is aromatic, the Pro side chain is aliphatic. B????????? His is an a-amino acid; Pro is an imino acid. C????????? the His side chain has a six-membered ring; Pro has a five-membered ring. D????????? the His side chain has a pK around pH = 7; the Pro side chain does not. E????????? All but the third choice are significant differences.
10. A significant difference between Phe and Tyr is that A????????? the Phe side chain is aromatic, the Tyr side chain is aliphatic. B????????? Tyr is an a-amino acid; Phe is an imino acid. C????????? the Tyr side chain has an -OH group; the Phe side chain does not. D????????? the Tyr side chain has a pK around pH = 7; the Phe side chain does not. E????????? All but the third choice are significant differences.  5 ※<3> 1. The peptide bond in proteins is A????????? planar, but rotates to three preferred dihedral angles. B????????? nonpolar, but rotates to three preferred dihedral angles. C????????? nonpolar, and fixed in a trans conformation. D????????? planar, and usually found in a trans conformation. E????????? not cleavable by hydrolysis.
2. The molecular formula for glycine is C2H5O2N. What would be the molecular formula for a linear oligomer made by linking ten glycine molecules together by condensation synthesis? A????????? C20H50O20N10. B????????? C20H32O11N10. C????????? C20H40O10N10. D????????? C20H68O29N10. E????????? None of the above.
3. The resonance structures that can be drawn for the peptide bond indicate that the peptide bond A????????? still isn't completely understood by chemists. B????????? is stronger than an ordinary single bond. C????????? has partial double bond character. D????????? actually extends to the a-carbon. E????????? The second and third choices are both correct.
4. The peptide hormone involved in controlling blood pressure is: A????????? testosterone. B????????? oxytocin. C????????? vasopressin. D????????? interferon B. E????????? glutathione.
5. Aspartame, the synthetic sweetener (a.k.a. NutraSweet), is A????????? a dipeptide. B????????? also secreted by the posterior pituitary gland in response to thirst. C????????? a glucose derivative. D????????? not digested (i.e. hydrolyzed) by humans. E????????? is nearly 10,000-fold sweeter than sucrose, by weight.  5 ※<4> 1. The peptide, Val-Lys-Glu-Met-Ser-Trp-Arg-Ala, was digested with cyanogen bromide (CNBr) to produce A?????????? Val-Lys ? + ? Glu-Met-Ser ? + ? Trp-Arg-Ala. B?????????? Val-Lys-Glu-Met-Ser-Trp ? + ? Arg-Ala. C?????????? Val-Lys-Glu-Met ? + ? Ser-Trp-Arg-Ala. D?????????? Val-Lys-Glu ? + ? Met-Ser-Trp-Arg-Ala. E?????????? Val-Lys-Glu-Met-Ser ? + ? Trp-Arg-Ala.
2. The same peptide, Val-Lys-Glu-Met-Ser-Trp-Arg-Ala, was digested with chymotrypsin to produce: A?????????? Val-Lys ? + ? Glu-Met-Ser ? + ? Trp-Arg-Ala. B?????????? Val-Lys-Glu-Met-Ser-Trp ? + ? Arg-Ala. C?????????? Val-Lys-Glu-Met-Ser ? + ? Trp-Arg-Ala. D?????????? Val-Lys-Glu ? + ? Met-Ser-Trp-Arg-Ala. E?????????? Val-Lys-Glu-Met ? + ? Ser-Trp-Arg-Ala.
3. Hydrogen bonds in a-helices are A?????????? more numerous than Van der Waals interactions. B?????????? not present at Phe residues. C?????????? analogous to the steps in a spiral staircase. D?????????? roughly parallel to the helix axis. E?????????? about 5? in length.
4. In b-pleated sheet structures A?????????? neighboring chains lie in a flat plane. B?????????? neighboring residues are hydrogen bonded. C?????????? neighboring chains are connected by a-helices. D?????????? neighboring residues have F & Y angles of about 90°. E?????????? neighboring chains are hydrogen bonded.
5. If the F and Y angles of each peptide unit in a protein are known, the following will also be determined: A?????????? complete secondary structure. B?????????? complete tertiary structure. C?????????? complete quaternary structure. D?????????? thermodynamic stability. E?????????? Both the first and the second choices are correct.  5 ※<5> 1. Which of the following is an example of tertiary structure in a protein? A????????? polyalanine. B????????? a multimeric protein. C????????? an a-helix. D????????? a b-pleated sheet. E????????? a globular domain.
2. An "oil drop with a polar coat" is a metaphor referring to the three dimensional structure of: A????????? fibrous proteins. B????????? collagen. C????????? globular proteins. D????????? silk protein. E????????? The first and the second choice are both correct.
3. The portion of proteins having the highest mobility are A????????? a-helices. B????????? b-sheets. C????????? peptide bonds. D????????? surface side chains. E????????? aliphatic groups.
4. Which of the following is most correct: A????????? Charged amino acids are never buried in the interior of a protein. B????????? Charged amino acids are seldom buried in the interior of a protein. C????????? All hydrophobic amino acids are buried when a protein folds. D????????? Tyrosine is only found in the interior of proteins. E????????? Glycine is rarely found in proteins because it is too destabilizing.
5. Disulfide bonds most often stabilize the native structure of: A????????? extracellular proteins. B????????? dimeric proteins. C????????? hydrophobic proteins. D????????? intracellular proteins. E????????? multisubunit proteins.
6. Buried hydrophobic sidechains in a globular protein fit into a "hole" formed by the sidechains of A????????? 1-3 other amino acids. B????????? precisely six other amino acids. C????????? 5-7 other amino acids. D????????? 9-12 other amino acids. E????????? 13-15 other amino acids. 7. The most important parameter relating to the energy of a H-bond in protein structure is: A????????? whether it is found in an a-helix or a b-sheet. B????????? the angle between donor and accepter, i.e. 180° +/- 20°. C????????? the distance between donor and accepter, i.e. <3.2?. D????????? the peptide bond dipole, i.e. - 3.70 D. E????????? the planarity of the peptide bond.
8. All other things being equal, the free energy of favorable electrostatic interaction between two charges separated by 4? (-4kJ/mol) will A????????? decrease 2-fold at 2? separation. B????????? decrease 4-fold at 2? separation. C????????? remain about the same. D????????? increase 2-fold at 2? separation. E????????? increase 4-fold at 2? separation.
9. Attractive van der Waals forces occur A????????? between apolar molecules in the liquid state. B????????? between any pair of nearby atoms. C????????? between polar molecules in the solid state. D????????? only if other forces are less favorable. E????????? only in the gas phase.
10. Unpaired H-bond donors and acceptors are found in the hydrophobic core of a protein A????????? only at the ends of a-helices. B????????? only at the turns connecting b-strands. C????????? only on Pro residues. D????????? about once or twice/protein. E????????? only very rarely.
11. All other things being equal, the free energy of an unfavorable electrostatic interaction between two charges separated by water (e = 80) will A????????? decrease 20-fold in benzene (e = 4). B????????? decrease 400-fold in benzene. C????????? remain about the same. D????????? increase 20-fold in benzene. E????????? increase 400-fold in benzene.  5 ※<6> 1. The strong conclusion from Anfinsen's work on RNaseA was that: A????????? 100% enzyme activity corresponds to the native conformation. B????????? disulfide bonds (S-S) in proteins can be reduced in vitro. C????????? Cys-SH groups are not found in vivo. D????????? the native conformation of a protein is adopted spontaneously. E????????? irreversible denaturation of proteins violates the "Thermodynamic Hypothesis".
2. Treatment of RNaseA with 8M urea, but without adding mercaptoethanol would A????????? not have unfolded the protein. B????????? have simplified the experimental analysis. C????????? also denature the enzyme. D????????? have caused irreversible denaturation. E????????? also result in formation of Cys-SH residues.
3. If Anfinsen had not determined the location of the S-S bonds in renatured RNaseA, his result of >90% recovery of enzyme activity would A????????? have proven his hypothesis. B????????? not have been believed. C????????? not have been possible. D????????? have been hard to believe. E????????? have gone unnoticed.
4. The statement (from Campbell, p.127) that "the amino acid sequence of a protein contains all of the information required for the complete three dimensional structure" A????????? cannot be falsified by experiment; hence it is trivial. B????????? is strongly supported by many denaturation-renaturation experiments. C????????? is called an "hypothesis" since its validity is sort of dicey. D????????? is called a "model" because it can be diagrammed in textbooks. E????????? has essentially been proven by recent theoretical work.
5. Anfinsen probably chose RNaseA for his experiments instead of say, trypsin or chymotrypsin, because A????????? trypsin would digest itself to oligopeptides under mildly denaturing conditions (slow removal of urea). B????????? RNaseA is less expensive than trypsin or chymotrypsin. C????????? Trypsin and chymotrypsin are intracellular enzymes (no S-S bonds). D????????? RNaseA has only 25 amino acid residues. E????????? RNaseA does not have any interfering His residues.
6. Which of the following occurred when RNaseA refolded? A????????? The primary structure of the protein was rearranged. B????????? Most of the charged residues were found buried in the protein. C????????? The entropy of the protein increased. D????????? All of the above. E????????? None of the above.  5 ※<7> 1. Cleavage of an IgG molecule by the protease, papain, produces: A????????? an antigen-binding site and two constant regions. B????????? two heavy chain-light chain dimers. C????????? an inactive mixture of oligopeptides. D????????? two Fab fragments and one Fc fragment. E????????? an antibody without its N-linked oligosaccharide.
2. Antibodies of the IgG class A????????? consist of four subunits. B????????? are glycoproteins. C????????? have inter- and intra-chain disulfide crosslinks. D????????? are secreted into the bloodstream. E????????? All four choices are correct.
3. The immunoglobulin fold is A????????? found only in IgG molecules. B????????? composed of two antiparallel b-strands folded into a globular domain. C????????? a b-barrel composed of a three- and a four-stranded antiparallel b-sheet. D????????? found six times in the IgG molecule. E????????? The third and fourth choices are both correct.
4. Antigenic determinants bind to which portions of an antibody? A????????? variable regions. B????????? constant regions. C????????? only light chains. D????????? only heavy chains. E????????? the effector region.
5. Monoclonal antibodies produced in the laboratory A????????? lack the constant regions of IgG. B????????? cannot be used for disease diagnosis yet. C????????? derive from human cancer patients. D????????? can be selected to bind to almost any known molecule. E????????? None of the above are correct.
6. Antibodies in the human immune system can identify approximately 108 different molecules. Which one of the following is true? A????????? This diversity is generated from 108 different immunoglobin genes. B????????? Most of these antibodies recognize self-antigens. C????????? Most of these antibodies recognize proteins. D????????? Most of these antibodies recognize small organic molecules. E????????? There are really just a small number of antibodies, each of which can bind to many different antigens. F????????? have gone unnoticed.  5 ※<8> 1. The specificity of a ligand binding site on a protein is based on: A????????? the absence of competing ligands. B????????? the amino acid residues lining the binding site. C????????? the presence of hydrating water molecules. D????????? the opposite chirality of the binding ligand. E????????? the similar size and shape of protein and ligand.
2. When binding data are analyzed in a Scatchard plot (n/[L] vs n), the slope is used to estimate ___; and the X-axis intercept is used to estimate ___. A????????? the Kd; ? and the rate of dissociation. B????????? the binding stoichiometry; ? and the Kd. C????????? the Kd; ? and the fractional occupation of sites. D????????? the Kd; ? and the binding stoichiometry. E????????? None of the above; ? only the y-axis is useful.
3. Once a ligand dissociation constant (Kd) has been determined it is possible to calculate A????????? the ligand binding constant (Ka). B????????? the DG for the binding interaction. C????????? the enthalpy of the binding interaction. D????????? the concentration of ligand required for half-maximal occupancy. E????????? All but the third choice are correct.
4. A monoclonal antibody (Mab) specific for the 2,4-dinitrophenyl (DNP) hapten might also bind one of these pairs of amino acids: A????????? Leu or Ile B????????? His or Pro C????????? Tyr or Phe D????????? Ser or Thr E????????? Cys or Met
5. If the Mab of Question 4 binds p-nitrophenol with a Ka =106 M-1, what is the most likely measured Kd in the presence of a competing amino acid? (Appropriate units were deliberately removed from the choices.) A????????? Kd = 10-5 B?????????? Kd = 105 C????????? Kd = 10-6 D????????? Kd = 106 E????????? Kd = 10-7  5 ※<9> 1. The dissociation constant is A????????? a measure of how easily the alpha and beta subunits combine to form hemoglobin. B????????? the inverse of the Hill coefficient. C????????? the inverse of the association constant. D????????? related to the enthalphy change due to ligand binding. E????????? related to the entropy change due to ligand binding.
2. The Hill coefficient (nH) for myoglobin is ____; whereas nH is about ___ for hemoglobin. A????????? 2.8; ? 1.0 B????????? 1.0; ? 2.8 C????????? 1.0; ? 4.0 D????????? 4.0; ? 1.0 E????????? None of the above choices are correct.
3. When pO2 = p50 of myoglobin, the fractional saturation (YO2) is about: A????????? 0.1 B????????? 0.3 C????????? 0.5 D????????? 0.7 E????????? 0.9
4. Allosteric effects that occur in hemoglobin A????????? only occur in humans. B????????? are important for maintaining Fe in the Fe2+ state. C????????? minimize oxygen delivery to the tissues. D????????? optimize oxygen delivery to the tissues. E????????? can also be observed in myglobin.
5. The cooperativity of O2 binding to hemoglobin results in a A????????? 100-fold higher affinity for the last O2 bound than for the first. B????????? 100-fold lower affinity for the last O2 bound than for the first. C????????? extensive protein conformational change. D????????? release of H+ with the dissociation of O2. E????????? The first and third choices are both correct.
6. When p02 = 10*p50 of myoglobin, the fractional saturation (YO2) is about: A????????? 0.1 B????????? 0.3 C????????? 0.5 D????????? 0.7 E??????? 0.9
7. When p02 = 0.1*p50 of myoglobin, the fractional saturation (YO2) is about: ?????? A????????? 0.1 B????????? 0.3 C????????? 0.5 D????????? 0.7 E????????? 0.9
8. The following small molecules affect hemoglobin as indicated: A????????? Decreased [H+] and [N3-] decrease Hb affinity for O2. B????????? Increased [H+] and [C1-] increase Hb affinity for O2. C????????? Increased [C0] and [C1-] increase Hb affinity for O2. D????????? Increased [H+] and [C1-] decrease Hb affinity for O2. E????????? Decreased [bisphosphoglycerate] (BPG) decreases the affinity for O2.
9. The slope of a Hill plot for hemoglobin ___; whereas that for myoglobin ___. A????????? is about 3; is 1.0. B????????? decreases at low p02; is constant at all p02. C????????? increases at high p02; curves upward for all p02. D????????? is 1.0; is about 4. E????????? The first and second choices are both correct.
10. In deoxy hemoglobin (Hb), the Fe (II) is 5-coordinated to A????????? four nitrogens of heme and to the proximal His of Hb. B????????? four nitrogens of heme and to a water molecule. C????????? four nitrogens of heme and to an O2 molecule. D????????? two nitrogens of heme and to three His residues in Hb. E????????? two nitrogens of heme and to three water molecules.
11. Spontaneous oxidation of the heme-bound Fe(II) to Fe(III) is prevented in hemoglobin by A????????? the symmetry of its quaternary structure. B????????? the four heme-protein covalent bonds. C????????? a highly-ordered water molecule within the heme pocket. D????????? the surrounding protein structure in each subunit. E????????? methemoglobin reductase.
12. In sickle cell anemia, the basis of the malfunction of the hemoglobin molecule is: A????????? incorrect secondary structure. B????????? substitution of a single amino acid. C????????? faulty binding of the heme groups. D????????? reduced affinity for oxygen. E????????? insufficient iron in the diet.  5 ※<10> 1. Hydrogen atoms are not shown in X-ray structures of proteins because A????????? hydrogen, with only one electron, is almost invisible. B????????? everyone knows where hydrogen belongs in a structure. C????????? including hydrogens would make the models too confusing. D????????? hydrogen just isn't that important. E????????? The first two choices are both correct.
2. The following is usually calculated directly from X-ray diffraction data: A????????? The number of electrons in the crystal. B????????? The electron density at different locations in the crystal. C????????? The x, y, z coordinates of each atom. D????????? The size of the protein in the crystal. E????????? The strength of the X-ray beam used in the experiment.
3. At which of the following resolutions would you first be able to clearly define the f (phi) and y (psi) angles from the crystal structure? A????????? 5 Angstroms. B????????? 4 Angstroms. C????????? 3 Angstroms. D????????? 2 Angstroms. E?????????
1 Angstrom.
4. The position and the intensity of a peak in the NMR spectrum of a protein (intensity plotted vs. chemical shift) provide information on: A????????? The primary sequence of the protein. B????????? The number of protons absorbing energy at that frequency. C????????? A single proton. D????????? The local environment (electron density) of each proton. E????????? The second and fourth choices are both correct.
5. The pKa of an ionizable side chain, such as imidazole in histidine, can be determined with NMR because A????????? the pKa is near neutrality. B????????? protonated imidazole has twice the number of protons. C????????? unprotonated imidazole is invisible in the spectrum. D????????? the chemical shift of His differs from His+. E????????? None of these choices are correct.
6. The NMR spectrum of a mixture of protonated and unprotonated His shows a single absorption line because A????????? unprotonated imidazole is invisible in the spectrum. B????????? rapid exchange of the two forms causes averaging of the chemical shift. C????????? the two lines are broad and overlapping. D????????? the two lines have the same chemical shift. E????????? none of the above.
7. Evidence that crystal structures correspond closely to the solution structures of proteins include: A????????? a protein crystal with ~50% water content is essentially 'in solution'. B????????? different crystal forms of several proteins yield the same structure. C????????? solution NMR structures of several proteins yield the same structure as the crystal structure. D????????? many enzymes are catalytically active in the crystalline state. E????????? All four choices are correct.
8. At which of the following resolutions would you first be able to trace the peptide backbone and determine the secondary structure of the protein? A????????? 5 Angstroms. B????????? 4 Angstroms. C????????? 3 Angstroms. D????????? 2 Angstroms. E????????? 1 Angstrom.
9. Myoglobin readily binds oxygen. However, the crystal structure of myoglobin does not have a channel large enough for oxygen to reach the iron atom within the heme group. The ability of myoglobin to bind oxygen can be explained by: A????????? Quantum mechanical tunneling of the oxygen. B????????? The oxygen molecule forms individual atoms which are smaller. C????????? Small motions in the protein enlarge the channel. D????????? The heme group leaves myoglobin to bind the oxygen. E????????? The crystal structure is grossly incorrect  5 ※<11> 1. After disrupting the yeast cells, which of the following might you add to stabilize the protein? A????????? NaCl B????????? Protease Inhibitor. C????????? ATP. D????????? AMP. E????????? All of the above.
2. Fractional precipitation is the next step. BC-1ase precipitates between 2.5-3.5 M added salt. Which of the following salts do you choose to use? A????????? silver chloride, AgCl. B????????? ammonium perchlorate, NH4ClO4. C????????? ammonium sulfate, (NH4)2SO4. D????????? barium perchorate, Ba(ClO4)2. E????????? guanidinium chloride, CN3H6Cl.
3. The precipitate from step 2 is dissolved in buffer, pH=7.0. The high salt concentration is removed by passing the solution through a gel filtration column. The protein is expected to: A????????? elute from the column after the residual salt. B????????? elute before the residual salt. C????????? stick to the column. D????????? remain at the top of the column. E????????? Any of the above choices are possible.
4. The desalted protein solution from the gel filtration column is next applied to an ion exchange column. The best results are expected from a column that contains A????????? anion exchange resin, pH 7.0. B????????? anion exchange resin, pH 3.0. C????????? cation exchange resin, pH 7.0. D????????? cation exchange resin, pH 8.0. E????????? cation exchange resin, pH 10.0.
5. The fractions obtained from the ion exchange column are nearly pure BC-1ase. To estimate the homogeneity of the preparation which of the following tests are suitable: A????????? polyacrylamide gel electrophoresis (PAGE), native conditions. B????????? SDS-PAGE. C????????? isoelectric focusing. D????????? determination of specific activity. E????????? All of the above choices are valuable tests for purity.
6. To finish the purification step you prepare an affinity column using AMP bound to the column resin (beads). Which of the following methods would be the best to remove the bound protein from the column? A????????? Urea, in sufficient quantities to denature the protein. B????????? Changing the pH. C????????? Washing the column with AMP. D????????? Washing the column with high salt. E????????? Washing the column with distilled water.
7. What would be the best way to determine the location of this protein in the column fractions? A????????? UV absorption. B????????? Changes in the refractive index. C????????? Measure the rate of ATP synthesis. D????????? SDS gel electrophoresis of the protein. E????????? Mass spectroscopy of the protein.
8. The void volume of the gel filtration column, Vo, is 30 mL. A monomeric protein with a known molecular weight of 25 kDa elutes at a volume of 45 mL. The protein that you are trying to purify elutes at a volume of 35 mLs. Which of the following is most likely to be true: A????????? Your protein is repelled by the gel filtration material. B????????? Your protein is not monomeric in solution. C????????? Your lab partner mixed up the tubes. D????????? Your protein is monomeric also. E????????? Your protein has been digested by proteases during the purification.
9. In an SDS-PAGE experiment proteins are separated on the basis of their: A????????? negatively charged sidechains. B????????? charge-to-mass ratio. C????????? molecular weight. D????????? positively charged sidechains. E????????? different isoelectric points.
10. Electrophoresis of histones (pI = 8.5) and myoglobin (pI = 5.5) under non-denaturing conditions (pH = 7.0) results in: A????????? histones migrate to the cathode (-); myoglobin migrates to the anode (+). B????????? histones migrate to the anode (+); myoglobin migrates to the cathode (-). C????????? both proteins migrate to the anode (+). D????????? both proteins migrate to the cathode (-). E????????? smearing of the similarly charged bands.
11. The subunit molecular weight as well as the number of subunits in the quaternary structure can be determined by: A????????? SDS-PAGE electrophoresis. B????????? Isoelectric focusing. C????????? Gel filtration chromatography. D????????? combining information from a) and c). E????????? combining information from a) and b).
12. In a gel filtration column: A????????? Smaller proteins enter the beads more readily. B????????? Large proteins elute first. C????????? Small proteins elute first. D????????? Large proteins enter the beads more readily. E????????? both a) and b)
13. In an SDS-PAGE Gel: A????????? Proteins are denatured by the SDS. B????????? Proteins have the same charge-to-mass ratio C????????? Smaller proteins migrate more rapidly through the gel. D????????? Larger proteins migrate more slowly through the gel. E????????? All of the above.  5 ※<12> 1. The molecular formula for glucose is C6H12O6. What would be the molecular formula for a polymer made by linking ten glucose molecules together by dehydration synthesis? A????????? C60H120O60. B????????? (C6H12O6)10. C????????? C60H102O51. D????????? C60H100O50. E????????? None of the above.
2. Monosaccharides, such as ribose, fructose, glucose, and mannose differ significantly in A????????? their sweetness. B????????? the positions of their carbonyl groups. C????????? their diastereomeric configurations. D????????? their number of carbon atoms. E????????? All but the first choice are significant differences.
3. Boat and chair conformations are found A????????? in pyranose sugars. B????????? in furanose sugars. C????????? in any sugar without axial -OH groups. D????????? in any sugar without equatorial -OH groups. E????????? only in a-D-glucopyranose.
4. Which of the following is an example of a storage polysaccharide made by animals? A????????? cellulose. B????????? glycogen. C????????? collagen. D????????? amylopectin. E????????? starch.
5. Cellulose, a b(1->4)-linked glucose polysaccharide, differs from starch in that starch is A????????? a b(1->6)-linked manose polysaccharide B????????? a b(1->6)-linked glucose polysaccharide. C????????? an a(1->6)-linked glucose polysaccharide. D????????? an a(1->4)-linked glucose polysaccharide. E????????? an a(1->4)-linked mannose polysaccharide.
6. The glycosidic bond A????????? joins glucose and fructose to form sucrose. B????????? in sucrose is hydrolyzed by bees to make honey from nectar. C????????? in maltose is not hydrolyzed in "lactose intolerant" humans. D????????? in lactose is hydrolyzed by human infants to make two galactose monosaccharides. E????????? The first two choices are both correct.
7. Cellulose fibers resemble ___ in proteins; whereas a-amylose is similar to ___. A????????? a-helices; b-sheets. B????????? b-sheets; a-helices. C????????? b-sheets; the hydrophobic core. D????????? a-helices; b-turns. E????????? b-turns; coiled-coils.
8. The N-linked glycoproteins of eukaryotes usually have a N-acetyl glucosamine (NAG) attached to A????????? a surface Asn residue. B????????? a surface Gln residue. C????????? a buried Asn residue. D????????? the amino terminal residue. E????????? the amino groups of Lys.
9. The O-linked glycoproteins of eukaryotes usually have their sugar chains attached to A????????? buried carbonyls in the protein backbone. B????????? surface carbonyls in the protein backbone. C????????? the OH of Ser or Thr residues. D????????? the carboxyl terminal residue. E????????? the carboxyl groups of Asp or Glu.
10. The NAG6 substrate is hydrolyzed by human lysozyme to form A????????? NAG5 + NAG. B????????? NAG4 + NAG2. C????????? NAG3 + NAG3. D????????? a mixture of the above products. E????????? 6 glucosamines + 6 acetic acids.
11. Which of the following does not contribute to lysozyme catalysis? A????????? the strained conformation of the "D sugar". B????????? the H-bond between the mainchain and O6 of NAG. C????????? the abnormally high pKa of Glu35. D????????? formation of a covalent intermediate at Ser 195. E????????? stabilization of the oxonium ion (carbocation) by Asp52.
12. Following stabilization of the transition state during lysozyme catalysis, the NAG4 product is released after A????????? attack of a water molecule on the oxonium ion. B????????? release of a water molecule from the glycosidic bond. C????????? breakdown of the tetrahedral intermediate at Ser 195. D????????? a major conformation change in the enzyme. E????????? the next substrate binds.  5 ※<13> 1. Phospholipids are molecules that contain: A????????? positively charged functional groups. B????????? long water-soluble carbon chains. C????????? cholesterol. D????????? hydrophilic heads and hydrophobic tails. E????????? The third and fourth answers are both correct.
2. Micelles of fatty acids in water are organized such that the ___ face the solvent and the ___ are directed toward the interior. A????????? hydrophilic heads; ? hydrophobic tails B????????? carboxylic acid groups; ? hydrocarbon chains C????????? hydrocarbon chains; ? carboxylic acid groups D????????? hydrophobic tails; ? hydrophilic heads E????????? The first and second answers are both correct.
3. The glycerophospholipids are composed of two fatty acids attached to glycerol and one of the following head groups: A????????? ethanolamine. B????????? choline. C????????? serine. D????????? threonine. E????????? All but the fourth choice are correct.
4. The lipid with the lowest energy value for human nutrition is: A????????? Cardiolipin. B????????? Olestra. C????????? Lecithin. D????????? Margarine. E????????? Olive oil.
5. Cholesterol is essential for normal membrane functions because it A????????? cannot be made by higher organisms, e.g. mammals. B????????? spans the thickness of the bilayer. C????????? keeps membranes fluid. D????????? catalyzes lipid flip-flop in the bilayer. E????????? plugs up the cardiac arteries of older men.  5 ※<14> 1. According to the fluid mosaic model of cell membranes, which type of molecule spans the membrane, from its inner to outer surface? A????????? carbohydrate. B????????? cholesterol. C????????? hydrocarbon tails. D????????? phospholipid. E????????? protein.
2. What are the membrane structures that function in active transport? A????????? peripheral proteins. B????????? carbohydrates. C????????? integral proteins. D????????? hydrophobic molecules. E????????? cholesterol.
3. All of the following are found in membranes except: A????????? nucleic acids. B????????? phospholipids. C????????? glycoproteins. D????????? glycolipids. E????????? steroids.
4. The membrane proteins that catalyze active transport reactions differ from soluble enzymes in that A????????? they do not enhance the rates of reaction. B????????? the product(s) of the reaction move in a specific direction. C????????? the substrate(s) of the reaction are all outside the cell. D????????? they are not specific. E????????? they are permanently changed during the reaction.
5. Which of the following is not an example of a lipid found in lipid-linked proteins? A????????? Farnesyl groups. B????????? Palmitic acid. C????????? Myristic acid. D????????? Stearic acid. E??????? Glycosylphosphatidylinositol.  5 ※<15> 1. Which of the statements regarding enzymes is false? A????????? Enzymes are proteins that function as catalysts. B????????? Enzymes are specific. C????????? Enzymes provide activation energy for reactions. D????????? Enzyme activity can be regulated. E????????? Enzymes may be used many times for a specific reaction.
2. The relationship between an enzyme and a reactant molecule can best be described as: A????????? a temporary association. B????????? an association stabilized by a covalent bond. C????????? one in which the enzyme is changed permanently. D????????? a permanent mutual alteration of structure. E????????? noncomplementary binding.
3. When [S] = KM, the velocity of an enzyme catalyzed reaction is about: A????????? 0.1*Vmax. B????????? 0.2*Vmax. C????????? 0.3*Vmax. D????????? 0.5*Vmax. E????????? 0.9*Vmax.
4. The active site of an enzyme A????????? remains rigid and does not change shape. B????????? is found at the center of globular enzymes. C????????? is complementary to the rest of the molecule. D????????? contains amino acids without sidechains. E????????? None of the above choices are correct.
5. The active site of an enzyme differs from an antibody-antigen binding site in that the enzyme active site A????????? contains modified amino acids. B????????? catalyzes a chemical reaction. C????????? is complementary to a specific ligand. D????????? contains amino acids without sidechains. E????????? None of the above are correct.
6. The transition state of a catalyzed reaction (EX?) is A????????? a highly-populated intermediate on the reaction pathway. B????????? higher in energy than that of an uncatalyzed reaction. C????????? lower in energy than that of an uncatalyzed reaction. D????????? lower in energy than the reaction substrate. E????????? bound very weakly to the catalyst.
7. The substrate KM in an enzyme-catalyzed reaction A????????? is usually less than Kd, the dissociation constant. B????????? is never less than Kd. C????????? cannot be equal to Kd. D????????? is estimated from the Y-intercept of a Lineweaver-Burk plot. E????????? cannot be derived from simple rate equations.
8. The initial velocity, vo, of an enzyme catalyzed reaction reaches Vmax A????????? at [S] = KM. B????????? at [S] = 10*KM. C????????? at 1/[S] = 1/KM. D????????? only as 1/[S] --> 0. E????????? The third and fourth choices are both correct.
9. When [S] = 0.1*KM, the velocity of an enzyme catalyzed reaction is about: A????????? 0.1*Vmax. B????????? 0.3*Vmax. C????????? 0.5*Vmax. D????????? 0.7*Vmax. E????????? 0.9*Vmax.
10. When [S] = 10*KM, the velocity of an enzyme catalyzed reaction is about: A????????? 0.1*Vmax. B????????? 0.3*Vmax. C????????? 0.5*Vmax. D????????? 0.7*Vmax. E????????? 0.9*Vmax.  5 ※<16> 1. A competitive inhibitor of an enzyme is usually: A????????? a highly reactive compound. B????????? a metal ion such as Hg2+ or Pb2+. C????????? structurally similar to the substrate. D????????? water insoluble. E????????? a poison.
2. An uncompetitive inhibitor of an enzyme catalyzed reaction A????????? binds to the Michaelis complex (ES). B????????? decreases Vmax. C????????? is without effect at saturating substrate concentration. D????????? can actually increase reaction velocity in rare cases. E????????? The first and second choices are both correct.
3. Which of the following common drugs is not a specific enzyme inhibitor? A????????? methotrexate. B????????? penicillin. C????????? sulfonilamide. D????????? iodine. E????????? Viagra.
4. A molecule of acetylcholinesterase normally hydrolyzes about 1,000 molecules of acetylcholine each second. After reacting with a nerve gas such as sarin, the hydrolysis rate of this enzyme would be about A????????? 10,000/sec. B????????? 1,000/sec. C????????? 100/sec. D????????? 10/sec. E????????? 0/sec.
5. An allosteric inhibitor of an enzyme usually A????????? binds to the active site. B????????? participates in feedback regulation. C????????? denatures the enzyme. D????????? causes the enzyme to work faster. E????????? is a hydrophobic compound.  5 ※<17> 1. A feature in common among all serine proteases is: A????????? a hydrophobic specificity pocket. B????????? a hydrophilic specificity pocket. C????????? a cluster of reactive serine residues. D????????? a single reactive serine residue. E????????? their amino acid sequence and tertiary structure.
2. Listed below alphabetically, are key events during trypsin hydrolysis of peptides: A????????? formation of the acylenzyme (acyl-E) B????????? release of amine product (amine P) C????????? release of carboxyl product (carboxyl P) D???????? tetrahedral intermediate (tet-I) The correct order of these events is: A????????? tet-I -> acyl-E -> carboxyl P -> tet-I -> amine P. B????????? acyl-E -> tet-I -> amine P -> tet-I -> carboxyl P. C????????? tet-I -> acyl-E -> amine P -> tet-I -> carboxyl P. D????????? acyl-E -> tet-I -> carboxyl P -> tet-I -> amine P. E????????? The first and third choices are both correct.
3. The pancreatic enzymes, trypsin, chymotrypsin and elastase all have: A????????? the same catalytic triad at their active sites. B????????? similar sequences and tertiary structures. C????????? the same catalytic mechanism. D????????? similar processing pathways from inactive zymogens. E????????? All of the above choices are correct.
4. The role of Asp 102 and His 57 during trypsin catalysis is: A????????? to function as a proton shuttle. B????????? to neutralize the charge on the other's sidechain. C????????? to keep the specificity pocket open. D????????? to move Ser 195 away from the scissile bond. E????????? to clamp the substrate into the active site.
5. The cleavage specificity of trypsin, chymotrypsin, and elastase depend in part on: A????????? the proximity of Ser 195 to the specificity pocket. B????????? the size, shape, and charge of the specificity pocket. C????????? the distance between the oxyanion hole and the specificity pocket. D????????? the presence of a low-barrier hydrogen bond in the specificity pocket. E????????? the absence of water in the specificity pocket.
6. The cleavage of trypsinogen to form active trypsin A????????? occurs in the small intestine. B????????? can be catalyzed by trypsin. C????????? occurs in the pancreas. D????????? can be catalyzed by chymotrypsin. E???????? The first two choices are both correct.
7. The catalytic triad of most serine proteases contains an Asp, His and Ser residue. Which of the following is true? A????????? The Asp residue is used in an acid catalyzed attack on the peptide bond. B????????? The His residue is responsible for the substrate specificity of Trypsin. C????????? The Ser residue is used in a nucleophilic attack on the peptide bond. D????????? The Asp residue is responsible for the substrate specificity of Trypsin. E????????? None of the above.
8. The proteolysis rate enhancement by chymotrypsin (~1010-fold) corresponds to a reduction in activation energy of about: A????????? 25 kJ/mol. B????????? 57 kJ/mol. C????????? 67 kJ/mol. D????????? 79 kJ/mol. E????????? 92 kJ/mol.
9. At saturating substrate concentrations, the rate limiting step in chymotrypsin hydrolysis of peptides is A????????? peptide binding. B????????? formation of the first tetrahedral intermediate. C????????? formation of the acylenzyme. D????????? release of the amine product. E????????? release of the carboxyl product.
10．Data for questions 4 and 5:Chymotypsin hydrolyses these two substrates:substrate kcat (sec-1) KM (mM) kcat/KM Tyr-Ala ? 8.0 ? 10 ? 800 Phe-Ala ? 4.0 ? 20 ? 200 . At saturating concentrations of both substrates, the ratio of Tyr:Phe products will be: A????????? 0.5. B????????? 1.0. C????????? 2.0. D????????? 4.0. E????????? 8.0.
11. At low concentrations (<<KM) of both substrates from question 4, the ratio of Tyr:Phe products will be: A????????? 0.5. B????????? 1.0. C????????? 2.0. D????????? 4.0. E????????? 8.0.  5 ※<18> 1. Which of the following statements is NOT a characteristic of catabolic reactions? A. They serve to generate energy. B. They often produce NADH or FADH2. C. They are divergent processes in which a few precursors form a wide variety of polymeric products. D. They often involve hydrolysis of macromolecules. E. Glycolysis is an example of a catabolic pathway.
2. A kinase is an enzyme that: A.?????? adds water to a double bond. B.?????? uses FADH2 to change the oxidation state of the substrate. C.?????? uses ATP to add a phosphate group to the substrate. D.?????? removes phosphate groups off of substrates
3. ATP A.???????? Is primarily produced in catabolism and used in biosynthesis B.???????? Has a high energy of hydrolysis partly because of electrostatic repulsion C.???????? Is rarely an allosteric effector D.???????? Is the highest energy compound in cells
4.If the (G` of the reaction A B is –12 kJ/mol, which of the following statements are correct? (Note the prime symbol means that a thermodynamic parameter is measured at pH.7.0) A.?????? The reaction will proceed spontaneously from left to right at the given conditions. B.??????? The reaction will proceed spontaneously from right to left at standard conditions. C.??????? The equilibrium constant favors the formation of B over the formation of A. D.?????? The equilibrium constant could be calculated if the initial concentrations of A and B were known. E.??????? The value of (G`o is also negative.
5. Which of the following statements about ATP and its roles in cells are true? A.???? The ATP molecule is kinetically unstable and is thus consumed within about one minute following its formation in cells. B.???? ATP provides free energy to a thermodynamically unfavorable reactions by group transfer, always donating a Pi to form a covalent intermediate. C.???? ATP can be regenerated by coupling with a reaction that releases more free energy than does ATP hydrolysis. D.???? A transmembrane proton-motive force can drive ATP synthesis. E.????? The active form of ATP is usually in a complex with Mg2+.
6.Indicate whether each of the following statements about ATP is true of false. (a)??? It contains a ?-N-glycosidic linkage. (b)??? It contains a furanose ring. (c)??? It is the highest-energy compound in cells. (d)??? It is used as a long-term storage form of energy in cells. (e)??? Its free energy of hydrolysis can be used to drive other reactions. (f)???? It is synthesized from ADP and Pi in an exergonic reaction. (g)??? It contains three phosphoanhydride bonds. (h)??? Repulsion between the negatively charged phosphoryl groups is reduced when ATP is hydrolyzed. (i)????? Its sugar moiety is glucose. (j)????? Its phosphoryl group transfer potential is higher than that of phosphoenolpyruvate.
7.Consider the general reaction A B, where (Go` = -60kJ/mol. Initially, 10 mM of A and 0 mM of B are present. After 24 hours, analysis reveals the presence of 2 mM of B and 8 mM of A. What can you conclude from this result? A.???????? A and B have reached equilibrium concentrations. B.???????? Formation of B is thermodynamically unfavorable. C.???????? The result described is impossible, given the of the reaction. D.???????? Formation of B is kinetically slow; equilibrium has not been reached at 24 hours. E.????????? An enzyme has shifted the equilibrium toward formation of A.
8. The standard free-energy changes for the reactions below are given: Phosphocreatine→?creatine + Pi , △G’= -43.0 kJ/mol , ATP→?ADP + Pi, △G’?= -30.5 kJ/mol, What is the overall △G’ for the following reaction? phosphocreatine + ADP →?creatine + ATP A. –12.5 kJ/mol B. +12.5 kJ/mol C. –74.0 kJ/mol D. +74.0 kJ/mol
9. A metabolite is: A. any stable product or intermediate within a biochemical pathway B. high-energy intermediate C. low-energy intermediate D. none of the above