中大生物化学试题2005秋季B卷

1、生物化学I（2005年秋季学期, B卷）专业(班级)： 姓名： 学号： 阅卷教师： 题号一二三四五六合计分数警示中山大学授予学士学位工作细则第六条：“考试作弊不授予学士学位”。 一、选择唯一正确答案（每小题2分，共30分）1. When the pH is 2 units below the pKa of a specific group, the ratio of protonated to unprotonated species in the solution isA) 10:1 in favor of the protonated form.B) 100:1 in favor of t

2、he unprotonated form.C) 1000:1 in favor of the unprotonated form.D) 100:1 in favor of the protonated form.E) Equal amount of the protonated and unprotonated forms.2. The titration curve shown below is most characteristic of the amino acid A) TyrosineB) ValineC) Glutamic acidD) LysineE) Glycine3. Whi

3、ch one of the local anesthetics shown below will exist to a greater extent in their protonated form at physiological pH (pH 7.4)?A) NovacaineB) LignocaineC) both Novacaine and Lignocaine will be fully deprotonatedD) both Novacaine and Lignocaine will be fully protonatedE) Novacaine and Lignocaine wi

4、ll be protonated to the same extent4. In a mixture of the five proteins listed below, which should elute second in size-exclusion (gel filtration) chromatography?A) cytochrome c, Mr = 13,000B) immunoglobulin G, Mr = 145,000C) ribonuclease A, Mr = 13,700D) RNA polymerase, Mr = 450,000E) serum albumin

5、, Mr = 68,5005. Which of the following best represents the backbone arrangement of two peptide bonds?A) Ca-N-Ca-C-Ca-N-Ca-CA) Ca-N-C-C-N-CaB) C-N-Ca-Ca-C-NC) Ca-C-N-Ca-C-ND) Ca-Ca-C-N-Ca-Ca-C 6Which one of the following statements regarding the carbohydrate structures shown below is FALSE?A) Carbohy

6、drate I has an a-1,4 linkage, whereas carbohydrate II has a b-1,4 linkage.B) Carbohydrate I and carbohydrate II are both characterized as having their free anomeric hydroxyls in the b conformation.C) Carbohydrate I and Carbohydrate II are both of the D-configuration.D) Carbohydrate I and Carbohydrat

7、e II are reducing carbohydrates.E) None of the above is FALSE.7The glucose storage polymer, glycogen, which is shown below in schematic format, is a polymer of _ linked chains of D-glucose with _ branches. It has _ reducing end(s) and _ non-reducing end(s). A) a-1,3, a-1,5, many, oneB) b-1,3, b-1,5,

8、 one, oneC) a-1,4, a-1,6, one, manyD) b-1,4, b-1,6, many, oneE) a-1,4, a-1,6, one, one8. Which one of the following statements is FALSE for BOTH myoglobin and hemoglobin?A) One molecule of O2 can bind per molecule of heme in the ferric form.B) Both are O2 transport proteins.C) O2 binding to hemoglob

9、in exhibits positive cooperativity while O2 binding to myoglobin is non-cooperative.D) Both myoglobin and hemoglobin bind H+ and exhibit the Bohr effect.E) Both myoglobin and hemoglobin are composed of four polypeptide chains. 9. With regard to amino acids, which statement is false?A) Amino acids ca

10、n act as proton donors and acceptors.B) All amino acids discovered in organism are L enantiomers.C) An L amino acid can be Dextrorotary.D) A conjugate acid/base pair is at its greatest buffering capacity when the pH equals its pK.E) Non-standard amino acids can be found in the hydrolysis product of

11、a protein.10. A mixture of Ala, Arg, and Asp in a pH 5.5 buffer was placed on a cation exchange column (the column is negatively charged) and eluted with the same buffer. What is the order of elution from the column? Use these pKa values: terminal COOH - 2, terminal NH3+- 9, R-amino - 10, R-COOH - 3

12、A) Arg, Ala then AspB) Arg, Asp then AlaC) Asp, Ala then ArgD) Asp, Arg then AspE) Ala, Asp then Arg11. A peptide was found to have a molecular mass of about 650 and upon hydrolysis produced Ala, Cys, Lys, Phe, and Val in a 1:1:1:1:1 ratio. The peptide upon treatment with Sanger's reagent (FDNB)

13、 produced NP-Cys and exposure to carboxypeptidase produced valine. Chymotrypsin treatment of the peptide produced a dipeptide that contained sulfur and has a UV absorbance, and a tripeptide. Exposure of the peptide to trypsin produced a dipeptide and a tripeptide. The sequence of the peptide isA) va

14、l-ala-lys-phe-cysB) cys-lys-phe-ala-valC) cys-ala-lys-phe-valD) cys-phe-lys-ala-valE) val-phe-lys-ala-cys12. With regard to protein structure, which statement is false?A) The dominant force that drives a water-soluble protein to fold is hydrophobic interaction.B) The number of hydrogen bonds within

15、a protein intends to be minimized.C) The conformations of a native protein are possibly the lowest energy state.D) The conformations of a native protein are countless.E) Disulfde bridges can increase the stability of a protein.13. Which protein has quaternary structure?A) Insulin.B) A natural antibo

16、dy.C) Chymotrypsin.D) Aspartate transcarbamoylase (ATCase).E) Myoglobin.14. Under physiological conditions, which of the following processes is not an important method for regulating the activity of enzymes?A) PhosphorylationB) Temperature changesC) AdenylationD) Allosteric regulationE) Protein proc

17、essing15. With regard to DNA, which statement is false?A) Triple helix and tetraplex tend to appear at sites where replication, recombination or transcription is initiated or regulated.B) Hydrogen bonds are the only force to stabilize DNA structure.C) The absorbance of DNA at 260 nm will rise when i

18、t is denatured.D) Z-DNA tracts may play an role in the regulation of the expression of some genes or in genetic recombination.E) B-DNA is the most stable structure in physiological condition. 二、看图填空（每小题5分，共30分）1. Protein secondary structures and their organization (5 points).A) Parallel b-pleated sh

19、eet;B) Antiparallel b-pleated sheet;C) Residues of Pro and Gly;D) Residues of Pro and Val;E) Residues of hydrophilic amino acids;F) Residues of hydrophobic amino acids;G) Residue of Arg, Lys, or His;H) Residue of Asp, or Glu.a) One domain of the protein is composed of b) What amino acids are frequen

20、tly found in 5 c) If the residues at 6 is positively charged, then the residue at 7 is best d) What residues occur mostly at 1 and 2? e) What residues occur mostly at 3 and 4? 2. Several oxygen dissociation curves are shown in the following figure. (5 points).Assume that curve C corresponds to purif

21、ied hemoglobin placed in a solution containing physiological concentrations of CO2 and BPG at a pH of 7.0. Below, indicate which of the curves reflects the changes noted in physiological conditions by placing the curve # on the lines below (Use only one curve choice / physiological change):a. Decrea

22、sed CO2 concentration_ b. Increase BPG concentration_ c. Dissociation of hemoglobin into subunits d. A mutation that eliminates ion pairs that stabilize the T or deoxygenated state e. Fetal hemoglobin or a mutation which increase binding affinity for oxygen 3. Kinetics of enzyme inhibition or double

23、-substrate reaction (5 points).a. Competitive inhibition b. Non-competitive inhibition c. Uncompetitive inhibition d. Mixed competitive inhibition If S2 and â substitute for I and á respectively, then:e. Double-substrate enzyme reaction involving a ternary complex f. Double-substrate enzym

24、e reaction with a ping-pong mechanism 4. Structure about Nucleotides and DNA (5 points) a. Exo-2´ / Endo-2´configuration of ribose b. Exo-3´ / Endo-3´configuration of ribose c. Hoogsteen Pairs d. Can form cruciform structure e. Can form H-DNA 5. Classes of membrane transports (5 points