中大生物化学试题秋季Word文件下载.docx

1、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 a protein.2. A mixture of Ala, Arg, and Asp in a pH 5.5 buffer was placed on a cation exchange co

2、lumn （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 - 3A） Arg, Ala then AspB） Arg, Asp then AlaC） Asp, Ala then ArgD） Asp, Arg then AspE） Ala, Asp then A

3、rg3. Proteins can be chromatographically separated by their different A） Charge.B） Molecular weight.C） Hydrophobicity.D） Affinity for other molecules.E） All of above.4. 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 ratio

4、. The peptide upon treatment with Sangers reagent （FDNB） 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 dipepti

5、de and a tripeptide. The sequence of the peptide isA） val-ala-lys-phe-cysB） cys-lys-phe-ala-valC） cys-ala-lys-phe-valD） cys-phe-lys-ala-valE） val-phe-lys-ala-cys5. With regard to protein structure, which statement is false?A） The dominant force that drives a water-soluble protein to fold is hydropho

6、bic interaction.B） The number of hydrogen bonds within 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.6. Which structure

7、 is unique to collagen?A） The alpha helix.B） The double helix.C） The triple helix.D） The beta structure.E） The beta barrel.7. Which protein has quaternary structure?A） Insulin.B） A natural antibody.C） Chymotrypsin.D） Aspartate transcarbamoylase （ATCase）.E） Myoglobin.8. Which of the following are bro

8、ad themes used in discussing enzyme reaction mechanisms?A） Proximity stabilizationB） Transition state stabilizationC） Acid-base catalysisD） Covalent catalysisE） All of the above9. Under physiological conditions, which of the following processes is not an important method for regulating the activity

9、of enzymes?A） PhosphorylationB） Temperature changesC） AdenylationD） Allosteric regulationE） Protein processing10. The conversion of glucose to pyruvate is a multistep process requiring ten enzymes. If a mutation occurs resulting in a lack of activity for one of these enzymes, which of the following

10、happens?A） The concentration of the metabolic intermediate which is the substrate of the missing enzyme is likely to increase and accumulateB） The concentration of pyruvate will increaseC） The cell will produce more of the other nine enzymes to maintain steady stateD） The concentration of the metabo

11、lic intermediate which is the product of the missing enzyme will decreaseE） A and D11. Indicate which is true about enzymes.A） Enzymes are permanently changed during the conversion of substrate into product.B） Enzymes interact irreversibly with their substrates.C） Enzymes change the energy differenc

12、e between substrates and products.D） Enzymes reduce the energy of activation for the conversion of reactant into product.E） Enzymes increase the energy content of the products.12. Consider a reaction as follows:A + B C + D, G0 = +10.0 Kj/molHow can this reaction go forward?A） Coupling of this reacti

13、on to a highly exergonic reaction through a common intermediate.B） Immediate removal of the products.C） Addition of the appropriate enzyme.D） A and B.E） All of the above.13. Which statement is not true of enzyme inhibitors? A） A competitive inhibitor binds the active site of the enzyme. B） Allosteri

14、c enzymes exhibit Michaelis-Menton kinetics. C） A noncompetitive enzyme binds elsewhere than the active site. D） Noncompetitive inhibitors cannot be completely overcome by adding more substrate. E） Competitive inhibition can be completely overcome by adding more substrate.14. You could most dramatically destabilize a duplex DNA molecule in an aqueous solution byA） Decreasing the temperature.B） Decreasing the concentration of salt.C） Decreasing the concentration of organic solvents.D） Adjusting the p