中山大学《生物化学》2017-2018学年期末试卷

中山大学生命科学学院试卷生物化学I（2017年秋季学期，A卷)专业（班级）：姓名：学号：阅卷教师：题号二三四五合计分数警示《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1.5分，共15分）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)Non-standard amino acids can be found in the hydrolysis product of a protein.2.In a highly acidic solution,pH=1.3,the dominant form of glycine is:A)NH2-CH2-COOH:B)NH3+-CH2-COOH;C)NH2-CH2-CO-;D)NH3*-CH2-COO-3.In the isoelectric form of a tetrapeptide:A)The amino and carboxyl termini are not charged.B)Two internal amino acids of the tetrapeptide cannot have ionizable R groups.C)The total net charge is zero.D)Only the amino and carboxyl termini contribute charge.4.Which would elute first from a gel-exclusion chromatographic column?A)a negatively charged protein of MW=40,000B)a positively charged protein of MW=40,000C)a protein at its isoelectric point of MW=30,000D)a polysaccharide of MW=100.0005.In an aqueous solution,protein conformation is determined by two major factors.One isthe formation of the maximum number of hydrogen bonds.The other is the:A)formation of the maximum number of hydrophilic interactions.B)maximization of ionic interactions.C)minimization of entropy by forming a water solvent shell around the protein.D)placement of all hydrophobic amino acid residues within the interior of the protein.6.You can destabilize a duplex DNA molecule in an aqueous solution byA)Decreasing the concentration of salt.