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 the1. 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 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 G`o is also negative.value of
Answer(s): A, D
2. 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 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 releas 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+.
Answer(s): C, D, E
3. A common moiety for NADP, NAD, FMN, FAD, and coenzyme A is: (2 points)
A. A pyrimidine ring;
清华少儿英语B. A three ring structure;
C. An ADP;
D. A pyrano ring;
E. A triphosphate group.
Answer(s): C
4. If the C-1 carbon of gluco were labeled with 14C, which of the carbon 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
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5. Which of the following are metabolic products of pyruvate in higher organisms? (2 points)
A. Glycerol
B. Lactic acid
C. Acetone
D. Acetyl-CoA
E. Ethanol
Answer(s): B, D
6. Indicate whether each of the following statements about the pento phosphate pathway is true (T) or fal (F). (5 points)
A. It generates NADH for reductive biosynthes. F
B. The reactions occur in the cytosol. T
C. Transketola and transaldola link this pathway to gluconeogenesis. F
D. It is more active in muscle cells than in fat-storage cells. F
E. It interconverts trios, tetros, pentos, hexos, and heptos. T
7. Which of the following statements are correct? The citric acid cycle (2 points)
A. does not exist as such in plants and bacteria, becau its functions 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 acids.
Answer(s): B, E
8. Match the cofactors of the pyruvate dehydrogena complex with their corresponding enzyme components and with their roles in the enzymatic steps that are listed. (5 points)
A. Coenzyme A: 3,7
B. NAD+: 2, 9
C. Thiamine pyrophosphate (TPP): 1, 5
D. FAD: 2, 6
E. Lipoamide: 3, 4,8
(1). Pyruvate dehydrogena component
(2). Dihydrolipoyl dehydrogena
(3). Dihydrolipoyl transacetyla
(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 different enzyme compone
nt.
(9). Oxidizes FADH2.
9. Matching the role in fatty acid oxidation and/or mobilization to the appropriate component listed below. (5 points)
A. Bile salt: 2
B. Serum albumin:5
C. ApoC-II:4
D. Apolipoprotein:3mr先生英文怎么读
E. Carnitine:1
(1). Acts as a “carrier” of fatty acids across the inner mitochondrial membrane.
(2). Acts as a biological detergent, disrupting fat globules into small mixed micelles.
(3). Binds and transports triacylglycerols, phospholipids, and cholesterol between organs.
(4). Activates lipoprotein lipa, which cleaves triacylglycerols into their components.
(5). Binds some fatty acids molibized from adipocytes and transports them in the blood to heart and skeletal muscle.
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10. Which of the following answers complete the ntence correctly? Surplus dietary amino acids may be converted into (2 points)
A. proteins.
B. Fats.
C. ketone bodies.
D. gluco.
E. a variety of biomolecules for which they are precursors.
Answer(s): A, B, C, D,E
11. Which of the following compounds rves as an acceptor for the amino groups of many amino acids during metabolism? (2 points)
A. Glutamine
B. Asparagine.
C. -ketoglutarate.
D. Oxaloacetate
E. Glutamate
Answer(s):C
12. 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 obrvations would not support 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 formation of a proton gradient across the inner mitochondrial membrane.
D. The orientation of the enzyme complexes of the electron transfer chain results in a unidirectional flow of H+.
E. Radioactively labeled inorganic phosphate is incorporated into cytosolic ATP only in the prence of an H+ gradient across the inner mitochondrial membrane.
Answer(s): B
14. Some photosynthetic prokaryotes u H2S, hydrogen sulfide, instead of water as their photosynthetic hydrogen donor. How does this change 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): C
15. Which of the following are constituents of chlorophylls? (2 points)
not fairA. Substituted tetrapyrrole.
B. Plastoquinone.
C. Mg2+.
D. Fe2+.
E. Phytol.
F. Iron porphyrin.
Answer(s): A, C, E
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16. The obrvation 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 condensing with some two-carbon acceptor. That acceptor was in fact which of the following? (2 points)
A. Acetate
B. Acetyl CoA
C. Acetyl phosphate
D. Acetaldehdyde
E. Glycerol phosphate
voodooF. None of the above
Answer(s): F
17. Which of the following are common features of the synthes of mevalonate (an intermediate of cholesterol biosynthesis) and ketone bodies? (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): A
18. S-adenosylmethionine is involved directly in which of the following reactions. (3 points)
A. Methyl transfer to phosphatidyl ethanolamine.
B. Synthesis of glycine from rine.
C. Synthesis of polyamines.
D. Conversion of homocysteine to methionine.
E. Generation of the 5` cap of the eukaryotic mRNAs.
Answer(s): A, C, E
19.Which of the following does not provide a carbon skeleton for the synthesis of amino acids? (2 points)
A. succinate.
-ketoglutarateB.
C. Pyruvate.
D. Oxaloacetate.
E. Ribo-5-phosphate.
Answer(s): A
20. Which of the following compounds directly provide atoms to form the 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, G
21. Which of the following statements about ribonucleotide reducta are true? (2 points)
A. It converts ribonucleoside diphosphates into 2`-deoxyribonucleoside 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 glutaredoxin.
E. It contains two kinds of allosteric regulatory sites: one for controlling the overall activity and the other for controlling the substrate specificity.
Answer(s): A, D, E
22. Biosynthetic pathways that require NADPH include which of the following? (2 points)
A. Gluconeogenesis.
B. Fatty acid biosynthesis.
C. Ketone body formation.
D. Cholesterol biosynthesis.
E. Tyrosine biosynthesis.八年级英语教案
Answer(s): B,D,E
23. 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 polymera.
H. DNA polymera I.
I. DNA liga.
J. dATP.
Answer(s): B, C, D, E, F, H, I, J
24. Which of the following statements about E. coli promoters are correct? (2 points)
A. They may exhibit different transcription efficiencies.
B. For most genes they include variants of connsus quences.
C. They specify the start sites for transcription on the DNA template.
D. They have identical and defining quences.
E. They are activated when C or G residues are substituted into their –10 regions by mutation.
F. Tho that have quences that correspond cloly to the connsus quences and are parated by 17 ba pairs are very efficient.
Answer(s): A, B, C, F
bequest25. The AAUAAA quence 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) quence is added.
D. The site where the relea factor will bind to end polypeptide synthesis.
E. The site where polyribonucleotide phosphoryla will add a stretch of random quences.
Answer(s): C
70 subunit of the26. The E. coli RNA polymera: (2 points)
A. acts as the catalytic site for polymerization.
B. Recognize promoters.
C. Has a proofreading function.
D. Increas the processivity of the enzyme.
E. Recognizes termination signals.
Answer(s): B
27. The discontinuity of eukaryotic genes were first revealed by: (2 points)
A. Using footprinting techniques.
B. DNA quence comparison.
C. RNA quence analysis.
D. Electron microscopic analysis of RNA-DNA hybrid molecules.
E. Plant genetic studies.
Answer(s): D
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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, E
29. A new compound, vivekine, was recently discovered by a clever undergraduate student. It was isolated from bacteria found in deep a-dwelling organisms. Vivekine inhi
bits protein synthesis in eukaryotes: Protein synthesis can initiate, but only dipeptides are formed and the remain bound to the ribosome. This toxin affects eukaryotic protein 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): B
30. Indicate whether each of the following statements about prokaryotic translation is true (T) or fal (F). (7 points)
A. An aminoacyl-tRNA syntheta catalyzes formation of an ester bond. ( T )
B. An mRNA molecule cannot be ud to direct protein synthesis until it has been completely transcribed. ( F )
C. The positioning of fMet-tRNA on the A site defines the reading frame. ( F )
D. Incoming aminoacyl-tRNA are first bound to the A site. ( T )
E. Formation of the 70S initiation complex requires an input of energy. ( 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. Relea factors cau the peptidyl transfera activity of the ribosome to u H2O as a substrate. ( T )
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how do you study for a test31. 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 oligonucleotide were incubated together, cleavage of the oligonucleotide occurred. When either the RNA or the oligonucleotide was incubated alon
e, there was no cleavage. When the RNA was incubated with higher concentrations of the oligonucleotide, saturation kinetics of the Michaelis-Menten type were obrved. Do the results demonstrate that the RNA has catalytic activity? Explain. (8 points)
Answer: The results alone do not establish that the RNA has catalytic activity. A catalyst must be regenerated. It is entirely possible that the results obrved could be accounted for by a stoichiometric, as oppod to a catalytic, interaction between RNA and the oligonucleotide. In which the RNA may “感谢室友不杀之恩commit suicide” as the oligonucleotide is cleaved. In such an interaction, a portion of the RNA would also be cleaved itlf as a part of the reaction. Four reaction products would accumulate, two resulting from the cleavage of RNA and two from 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 cour 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 quence on DNA to the production of protein by ribosomes, where precily does the process of translation occur? Explain. (6 points)
Answer: Translation involves conversion of the language of nucleotides to that of proteins. The agent of translation is the appropriate aminoacyl-tRNA syntheta, which must recognize a particular amino acid and link it to a tRNA containing an anticodon for that amino acid.
33.Suppo that a bacterial mutant is found to replicate its DNA at a very low rate. Upon analysis, it is found to have entirely normal activity of DNA polymeras I and III, DNA gyra, and DNA liga. It also 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 quence. What defect might account for the abnormally low rate of
DNA replication in this mutant? Explain. (6 points)
Answer: eleanorA decrea in the activity of prima would account for the low rate of DNA replication. DNA replication requires the prior synthesis of RNA primers. Decread rates of dNTP synthesis would also slow replication.
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