生化英文习题.docx

1、生化英文习题八年制复习资料一Question1. While studying the structure of a small gene that was recently sequenced during the Human Genome Project, an investigator notices that one strand of the DNA molecule contains 20 As, 25 Gs, 30 Cs, and 22 Ts. How many of each base is found in the complete double-stranded molec

2、ule?A. A = 40, G = 50, C = 60,T = 44B. A = 44, G = 60, C = 50,T = 40C. A = 45, G = 45, C = 52,T = 52D. A = 50, G = 47, C = 50,T = 47E. A = 42, G = 55, C = 55,T = 422. The base sequence of the strand of DNA used as the template for transcription has the base sequence GATCTAC. What is the base sequenc

3、e of the RNA product? (All sequences are written according to standard convention.)A. CTAGATGB. GTAGATCC. GAUCUACD. CUAGAUGE. GUAGAUC3. A four-year-old child who becomes easily tired and has trouble walking is diagnosed with Duchenne muscular dystrophy, an X-linked recessive disorder. Genetic analys

4、is shows that the patients gene for the muscle protein dystrophin contains a mutation in its promoter region. What would be the most likely effect of this mutation?A. Initialtion of dystrophin transcription will be deficient.B. Termination of dystrophin transcription will be deficient.C. Capping of

5、dystrophin mRNA will be defective.D. Splicing of dystrophin mRNA will be defective.E. Tailing of dystrophin mRNA will be defective.AnswerE. the two DNA strands are complementary to each other, with A base-paired with T, and G base paired with C. So, for example, the 20 As on the first strand would b

6、e paired with 20 Ts on the second strand, the 25 Gs on the first strand would be paired with 25 Cs on the second strand, and so forth. When these are all added together, the correct numbers of each base are indicated in choice G. Notice that, in the correct answer, A=T and G=CE. All sequences are wr

7、itten in the standard convention (5-3). The RNA product has a sequence that is complementary to the sequence of the template strand of DNA. Uracil (U) is found in RNA in place of the thymine (T) in DNA. Thus, the DNA template 5-GATCTAC-3 would produce the RNA product 3-CUAGAUG-5 or, written correctl

8、y in the standard direction, 5-GUAGAUC-3.A. Mutations in the promoter prevent formation of the RNA polymerase II transcription complex, and the initation of mRNA synthesis will be greatly decreased. A deficiency of dystrophin mRNA will result in a deficiency in the procduction of the dystrophin prot

9、ein,Which one of the following corredtly pairs an amino acid with a valid chemical characteristic?A. Glutamine: Contains a hydroxyl group in tis side chainB. Serine: Can form disulfide bondsC. Cysteine: Contains the smallest side chainD. Isoleucine: is nearly always found buried in the center of pro

10、teinsE. Glycine: Contains an aminde group in its side chainWhich one of the following statements concerning glutamine is correct?A. Contains three titratalbe groupsB. Is classified as an acidic amino acidC. Contains an amide groupD. Has E as its one-letter symbolE. Migrates to the cathode (negative

11、electrode ) during electrophoresis at pH 7.0A peptide bond:A. has a partial double-bond character.B. is ionized at physiologic pHC. is cleaved by agents that denature proteins, such as organic solvents an high concentrations of ureaD. is stale to heating in strong acidsE. occurs most commonly in the

12、 cis configuration.Which one of the following statements is correct?A. The -helix can be composed of more than one polypeptide chain.B. -sheets exist only in the antiparallel form.C. -Bends often contain proline.D. Motifs are a type of secondary structure.E. The -helix is stabilized primarily by ion

13、ic interactions between the side chains of amino acids.D. In proteins found in aqueous solutions, the side chains of the nonpolar amino acids, such isoleucine, tend to cluster together in the interior of the protein. Glutamine contains an amide in its side chain. Serine and threonine contain a hydro

14、xyl group in their side chain. Cysteine can form disulfide bonds. Glycine contains the smallest side chain.C. Glutamine contains two titratable groups, -carboxyl and -amino. Glutamine is a polar, neutral amino acid that shows little electrophoretic migration at pH 7.0. The symbol for glutamine is “Q

15、”.A. the peptide bond has a partial double-bond character. Unlike its components the -amino and -carboxyl groups the components of the peptide bond do not accept or give off protons. The peptide bond is not cleaved by organic solvents or urea, but is labile to strong acids. It is usually in the tran

16、s configurationC. -bends often contain proline, which provides a kink. The -helix differs from the -sheet in that it always involves the coiling of a single polypeptide chain. The -sheet occurs in both parallel and antiparallel forms. Motifs are elements of tertiary structure. The -helix is stabiliz

17、ed primarily by hydrogen bonds between the C=O and NH- groups of peptide bonds.Which one of the following statements about protein structure is correct?A. Proteins consisting of one polypeptide can have quaternary structure.B. The formation of a disulfide bond in a protein requires that the two part

18、icipating cysteine residues be adjacent to each other in the primary sequence of the protein.C. The stbility of quaternary structure in proteins is mainly a result of covalent bonds among the subunits.D. the denaturation of proteins always leads to irreversible loss of secondary and tertiary structu

19、re.E. The information required for the correct folding of a protein is contained in the specific sequence of amino acids along the polypeptide chain.An 80-year-old man presented with impairment of higher intellecutual function and alterations in mood and behavior. His family reproted progressive dis

20、orientation and memory loss over the last six months. There is no family history of dementia. The patient was tentatively diagnosed with Alzeheimer disease. Which one of the following best describes the disease?A. It is associated with -amyloid - an abnormal protein with an altered amino acid sequen

21、ce.B. It results from accumulation of denatured proteins that have random conformations.C. It is associated with the accumulation of amyloid precursor protein.D. It is associated with the accumulation of amyloid peptide aggregates.E. It is an environmentally produced disease uninfluenced by the gene

22、tics of the individual.A competitive inhibitor of an enzyme:A. increases Km without affecting VmaxB. dncreases Km without affecting VmaxC. increases Vmax without affecting KmD. dncreases Vmax without affecting Km E. dncreases both Km and VmaxE. The correct folding of a protein is guided by specific

23、interactions among the side chains of the amnin acid residues of a polypeptide chain. The two cysteine residues that react to form the disulfide bond may be a freat distaqnce apart in the primary structure (or on separate polypeptides), but are brought into close proximity by the three-dimensional f

24、olding of the polypeptide chain. Denaturation may either be reversible or irreversible. Quaternary structure requires more than one polypeptide chain. These chains associate through noncovalent interactions.D. Alzheimer disease is associated with long, fibrillar protein assemblies consisting of -ple

25、ated sheets found in the brain and elsewhere. The disease is associated with abnormal processing of a normal protein. The accumulated altered protein occurs in a -pleated sheet configuration that is neurotoxic. The A amyloid that is deposited in the brain in Alzheimer disease is derived by proteolyt

26、ic cleavages from the larger amyloid precursor protein -a single transmembrane protein expressed on the cell surface in the brain an other tissues. Most cases of Alzheimer disease are sporadic, although at least five to ten percent of cases are familial.A. In the presence of a competitive inhibitor,

27、 an enzyme appears to have a lower affinity for substrate, but as the substrate level is increased, the observed velocity approaches Vm.Which one of the following statements concerning the bingding of oxygen by hemoglobin is correct?A. The Bohr effect results in a lower affinity for oxygen at higher

28、 pH values.B. Carbon dioxide increases the oxygen affinity of hemoglobin by binding to the amino terminal groups of the polypeptide chains.C. The oxygen affinity of hemoglobin increases as the percent saturation increases.D. The hemoglobin tetramer binds four molecules of 2,3-BPG.E. Oxyhemoglobin an

29、d deoxyhemoglobin have the same affinity for protons (H+)The Michaelis constant, Km, is:A. numerically equl to 1/2 VmaxB. dependent on the enzyme concentrationC. independent of pHD. numerically equal to the substrate concentration thar gives half-maximal velocityE. increased in the presence of a non

30、competitive inhibitorsWhich one of the following statements concerning the components of the electron transport chain is correct?A. All of the components of the electron transport chain are present in large, multisubunit protein complexes embedded in the inner mitochondrial membrane.B. Oxygen direct

31、ly oxidizes cytochrome C.C. Succinate dehydrogenase directly reduces cytochrome C.D. The elecron transport chain contains some polypeptide chains coded for by the nuclear DNA and come coded for by mtDNAE. Cyanide inhibits electron folw, but not proton pumping or ATP synthesis.C. The binding of oxyge

32、n at one heme group increases the oxygen affinity of the remaining heme groups in the same molecule. Carbon dioxide decreases oxygen affinity because it lowers the pH; also bingding of carbon dioxide stabilizes the taut, deoxy form. Hemoglobin binds one molecule of 2,3-BPG. Deoxyhemoglobin has a greater affinity for protons and, therefor, is a weaker acid.D. Remember Km has the dimensions of concentration and is a characteristic of an enzyme under a given set of