生物化学期末考试试12套答案在最后(大学期末复习资料).doc

Name Class Score Biochemistry (I) Final Exam (fall, 2004) NOTE: You must write your answer on the answer sheet! Part I: For the following multiple choice questions, one answer is most appropriate (2.5(18 = 45 points). 1. With regard to amino acids, which statement is false? A) Amino acids can 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 a protein. 2. 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 A) Arg, Ala then Asp B) Arg, Asp then Ala C) Asp, Ala then Arg D) Asp, Arg then Asp E) Ala, Asp then Arg 3. 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 1:1:1:1:1 ratio. 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 dipeptide and a tripeptide. The sequence of the peptide is A) val-ala-lys-phe-cys B) cys-lys-phe-ala-val C) cys-ala-lys-phe-val D) cys-phe-lys-ala-val E) val-phe-lys-ala-cys 5. 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 b