清华本科生化考试 英文

清华大学本科生考试试题专用纸考试课程Biochemistry II 2001 年 6 月 11 日说明：1. 请选择正确答案，填在适当的横线处（1-30题）或写在答题纸上（31 -33题）；2. 答案可能是一个或多个；3. 每题的分数在标在了题目后面；4. 本卷满分为100.G` of the∆1. If 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) (2 points)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 stan dard conditions.C. The equilibrium constant favors the formation of B over the format ion of A.D. The equilibrium constant could be calculated if the initial concen trations of A and B were known.E. The G`o is also negative.∆value ofAnswer(s): A, D2. Which of the following statements about ATP and its roles in cells are true? (2 points)A. The ATP molecule is kinetically unstable and is thus consumed with in about one minute following its formation in cells.B. ATP provides free energy to a thermodynamically unfavorable reacti ons by group transfer, always donating a Pi to form a covalent interm ediate.C. ATP can be regenerated by coupling with a reaction that releases m ore 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+.Answer(s): C, D, E3. A common moiety for NADP, NAD, FMN, FAD, and coenzyme A is: (2 poi nts)A. A pyrimidine ring;B. A three ring structure;C. An ADP;D. A pyranose ring;E. A triphosphate group.Answer(s): C4. If the C-1 carbon of glucose were labeled with 14C, which of the c arbon atoms in pyruvate would be labeled after glycolysis? (2 points)A. The carboxylate carbon;B. The carbonyl carbon;C. The methyl carbon.Answer(s): C第页/共页5. Which of the following are metabolic products of pyruvate in highe r organisms? (2 points)A. GlycerolB. Lactic acidC. AcetoneD. Acetyl-CoAE. EthanolAnswer(s): B, D6. Indicate whether each of the following statements about the pentose phosphate pathway is true (T) or false (F). (5 points)A. It generates NADH for reductive biosyntheses. FB. The reactions occur in the cytosol. TC. Transketolase and transaldolase link this pathway to gluconeogenes is. FD. It is more active in muscle cells than in fat-storage cells. FE. It interconverts trioses, tetroses, pentoses, hexoses, and heptose s. T7. Which of the following statements are correct? The citric acid cyc le (2 points)A. does not exist as such in plants and bacteria, because its functio ns are performed by the glyoxylate cycle.B. oxidizes acetyl CoA derived from fatty acid degradation.C. produces most of the CO2 in anaerobic organisms.D. provides succinyl CoA for the synthesis of carbohydrates.E. provides precursors for the synthesis of glutamic and aspartic aci ds.Answer(s): B, E8. Match the cofactors of the pyruvate dehydrogenase complex with the ir corresponding enzyme components and with their roles in the enzymatic steps that are listed. (5 points)A. Coenzyme A: 3,7B. NAD+: 2, 9C. Thiamine pyrophosphate (TPP): 1, 5D. FAD: 2, 6E. Lipoamide: 3, 4,8(1). Pyruvate dehydrogenase component(2). Dihydrolipoyl dehydrogenase(3). Dihydrolipoyl transacetylase(4). Oxidizes the hydroxylethyl group(5). Decarboxylates pyruvate(6). Oxidizes dihydrolipoamide(7). Accepts the acetyl group from acetyllipoamide(8). Provides a long, flexible arm that coveys intermediates to diffe rent enzyme component.(9). Oxidizes FADH2.9. Matching the role in fatty acid oxidation and/or mobilization to t he appropriate component listed below. (5 points)A. Bile salt: 2B. Serum albumin:5C. ApoC-II:4D. Apolipoprotein:3E. Carnitine:1(1). Acts as a “carrier” of fatty acids across the inner mitochondr ial membrane.(2). Acts as a biological detergent, disrupting fat globules into sma ll mixed micelles.(3). Binds and transports triacylglycerols, phospholipids, and choles terol between organs.(4). Activates lipoprotein lipase, which cleaves triacylglycerols int o their components.(5). Binds some fatty acids molibized from adipocytes and transports them in the blood to heart and skeletal muscle.第页/共页10. Which of the following answers complete the sentence correctly? S urplus dietary amino acids may be converted into (2 points)A. proteins.B. Fats.C. ketone bodies.D. glucose.E. a variety of biomolecules for which they are precursors.Answer(s): A, B, C, D,E11. Which of the following compounds serves as an acceptor for the am ino groups of many amino acids during metabolism? (2 points)A. GlutamineB. Asparagine.C. -ketoglutarate.D. OxaloacetateE. GlutamateAnswer(s):C12. Match the functions for the coenzymes that are involved in amino acid metabolism. (4 points)A. Pyridoxal phosphate: (3)B. Coenzyme B12: (2)C. Tetrahydrobiopterin: (1)D. NAD+: (1)E. Biotin (4)(1). Carries electrons(2). Provides free radicals(3). Carries amino groups(4). Carries CO2.13. Which of the following experimental observations would not suppor t the chemiosmotic model of oxidative phosphorylation? (3 points) A. If mitochondrial membranes are ruptured, oxidative phosphorylation cannot occur.B. Raising the pH of the fluid in the intermembrane space results in ATP synthesis in the matrix.C. Transfer of electrons through the respiratory chain results in for mation of a proton gradient across the inner mitochondrial membrane.D. The orientation of the enzyme complexes of the electron transfer c hain results in a unidirectional flow of H+.E. Radioactively labeled inorganic phosphate is incorporated into cyt osolic ATP only in the presence of an H+ gradient across the inner mi tochondrial membrane.Answer(s): B14. Some photosynthetic prokaryotes use H2S, hydrogen sulfide, instead of water as their photosynthetic hydrogen donor. How does this chan ge the ultimate products of photosynthesis? (2 points)A. Carbohydrate (CH2O) is not produced.B. H2O is not produced.C. Oxygen is not produced.D. ATP is not produced.E. The products do not change.Answer(s): C15. Which of the following are constituents of chlorophylls? (2 point s)A. Substituted tetrapyrrole.B. Plastoquinone.C. Mg2+.D. Fe2+.E. Phytol.F. Iron porphyrin.Answer(s): A, C, E第页/共页16. The observation that the incubation of photosynthetic algae with 14CO2 in the light for a very brief time (5s) led to the formation of 14C-labeled 3-phosphoglycerate suggested that the 14CO2 was condensi ng with some two-carbon acceptor. That acceptor was in fact which of the following? (2 points)A. AcetateB. Acetyl CoAC. Acetyl phosphateD. AcetaldehdydeE. Glycerol phosphateF. None of the aboveAnswer(s): F17. Which of the following are common features of the syntheses of me valonate (an intermediate of cholesterol biosynthesis) and ketone bod ies? (2 points)A. Both involve 3-hydroxyl-3-methylglutaryl CoA (HMG-CoA).B. Both require NADPH.C. Both require the HMG-CoA cleavage enzyme.D. Both occur in the mitochondria.E. Both occur in liver cells.Answer(s): A18. S-adenosylmethionine is involved directly in which of the followi ng reactions. (3 points)A. Methyl transfer to phosphatidyl ethanolamine.B. Synthesis of glycine from serine.C. Synthesis of polyamines.D. Conversion of homocysteine to methionine.E. Generation of the 5` cap of the eukaryotic mRNAs.Answer(s): A, C, E19.Which of the following does not provide a carbon skeleton for thesynthesis of amino acids? (2 points)A. succinate.-ketoglutarate B.C. Pyruvate.D. Oxaloacetate.E. Ribose-5-phosphate.Answer(s): A20. Which of the following compounds directly provide atoms to form t he purine ring? (3 points)A. Aspartate.B. Carbamoyl phosphate.C. Glutamine.D. Glycine.E. CO2.F. N5,N10-methylenetetrahydrofolate.G. N10-formyltetrahydrofolate.H. NH4+.Answer(s): A, C, D, E, G21. Which of the following statements about ribonucleotide reductase are true? (2 points)A. It converts ribonucleoside diphosphates into 2`-deoxyribonucleosid e diphosphates in humans.B. It contains coenzyme B12, which generates free radicals needed for the catalysis.C. It accepts electrons directly from FADH2.D. It receives electrons directly from either thioredoxin or glutared oxin.E. It contains two kinds of allosteric regulatory sites: one for cont rolling the overall activity and the other for controlling the substr ate specificity.Answer(s): A, D, E22. Biosynthetic pathways that require NADPH include which of the fol lowing? (2 points)A. Gluconeogenesis.B. Fatty acid biosynthesis.C. Ketone body formation.D. Cholesterol biosynthesis.E. Tyrosine biosynthesis.Answer(s): B,D,E23. Homologous recombination in E. coli is likely to require which of the following? (3 points)A. DnaB protein.B. RecA protein.C. RecBCD complex.D. ATP.E. NAD+.F. Single-strand DNA binding protein.G. DNA-dependent RNA polymerase.H. DNA polymerase I.I. DNA ligase.J. dATP.Answer(s): B, C, D, E, F, H, I, J24. Which of the following statements about E. coli promoters are cor rect? (2 points)A. They may exhibit different transcription efficiencies.B. For most genes they include variants of consensus sequences.C. They specify the start sites for transcription on the DNA template.D. They have identical and defining sequences.E. They are activated when C or G residues are substituted into their–10 regions by mutation.F. Those that have sequences that correspond closely to the consensus sequences and are separated by 17 base pairs are very efficient. Answer(s): A, B, C, F25. The AAUAAA sequence on a RNA molecule marks (2 points)A. The site where ribosomes bind to initiate polypeptide synthesis.B. The site where transcription stops.C. The site near which the primary transcript is cleaved and a poly (A) sequence is added.D. The site where the release factor will bind to end polypeptide syn thesis.E. The site where polyribonucleotide phosphorylase will add a stretch of random sequences.Answer(s): C70 subunit of the 26. The E. coli RNA polymerase: (2 points)A. acts as the catalytic site for polymerization.B. Recognize promoters.C. Has a proofreading function.D. Increases the processivity of the enzyme.E. Recognizes termination signals.Answer(s): B27. The discontinuity of eukaryotic genes were first revealed by: (2 points)A. Using footprinting techniques.B. DNA sequence comparison.C. RNA sequence analysis.D. Electron microscopic analysis of RNA-DNA hybrid molecules.E. Plant genetic studies.Answer(s): D第页/共页28. Which of the following mRNA codons can be recognized by the tRNA anticodon ICG. (2 points)A. UGC.B. CGA.C. UGA.D. CGU.E. CGC.Answer(s): B, D, E29. A new compound, vivekine, was recently discovered by a clever und ergraduate student. It was isolated from bacteria found in deep sea-d welling organisms. Vivekine inhibits protein synthesis in eukaryotes: Protein synthesis can initiate, but only dipeptides are formed and t hese remain bound to the ribosome. This toxin affects eukaryotic prot ein synthesis by blocking the: (2 points)A. binding of formylmethionyl-tRNA to ribosomes.B. activity of elongation factors.C. activation of amino acids.D. recognition of stop signals.E. formation of peptide bonds.Answer(s): B30. Indicate whether each of the following statements about prokaryot ic translation is true (T) or false (F). (7 points)A. An aminoacyl-tRNA synthetase catalyzes formation of an ester bond. ( T )B. An mRNA molecule cannot be used to direct protein synthesis until it has been completely transcribed. ( F )C. The positioning of fMet-tRNA on the A site defines the reading fra me. ( F )D. Incoming aminoacyl-tRNA are first bound to the A site. ( T )E. Formation of the 70S initiation complex requires an input of energ y. ( T )F. The carboxyl group of the amino acid on the aminoacyl-tRNA is transferred to the amino group of a peptidyl-tRNA.( F )G. Release factors cause the peptidyl transferase activity of the rib osome to use H2O as a substrate. ( T )第页/共页31. In an attempt to determine whether a given RNA was catalytically active in the cleavage of a synthetic oligonucleotide, the following experimental results were obtained. When the RNA and the oligonucleot ide were incubated together, cleavage of the oligonucleotide occurred. When either the RNA or the oligonucleotide was incubated alone, ther e was no cleavage. When the RNA was incubated with higher concentrati ons of the oligonucleotide, saturation kinetics of the Michaelis-Ment en type were observed. Do these results demonstrate that the RNA has catalytic activity? Explain. (8 points)Answer: These results alone do not establish that the RNA has catal ytic activity. A catalyst must be regenerated. It is entirely possibl e that the results observed could be accounted for by a stoichiometri c, as opposed to a catalytic, interaction between RNA and the oligonu cleotide. In which the RNA may “commit suicide” as the oligonucleot ide is cleaved. In such an interaction, a portion of the RNA would al so be cleaved itself as a part of the reaction. Four reaction product s would accumulate, two resulting from the cleavage of RNA and two fr om the cleavage of the oligonucleotide. To show that this particular RNA was catalytic, it would be necessary to demonstrate that it turns over and is regenerated in the course of the reaction.32.Translation involves conversion of the language of nucleotides to that of proteins. In the chain of events leading from a nucleotide se quence on DNA to the production of protein by ribosomes, where precis ely does the process of translation occur? Explain. (6 points)Answer: Translation involves conversion of the language of nucleotid es to that of proteins. The agent of translation is the appropriate a minoacyl-tRNA synthetase, which must recognize a particular amino aci d and link it to a tRNA containing an anticodon for that amino acid.33.Suppose that a bacterial mutant is found to replicate its DNA at a very low rate. Upon analysis, it is found to have entirely normal ac tivity of DNA polymerases I and III, DNA gyrase, and DNA ligase. It a lso makes normal amounts and kinds of dnaA, dnaB, dnaC, and SSB proteins. The oriC region of its chromosome is found to be entirely normal with respect to nucleotide sequence. What defect might account for t he abnormally low rate of DNA replication in this mutant? Explain. (6 points)Answer: A decrease in the activity of primase would account for the low rate of DNA replication. DNA replication requires the prior synth esis of RNA primers. Decreased rates of dNTP synthesis would also slo w replication.第页/共页(中国生物论坛 copyright reserved)。