Practicetestkey - Practice multiple choice test...

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Practice multiple choice test Biochemistry 390 Spring 2009 1. Which of the following is not a biological role for amino acids? a. components of waxes b. function as neurotransmitters c. components of peptide hormones d. components of proteins e. All of the above are biological uses of amino acids. 2. Which of the following statements about aromatic amino acids is correct? a. On a molar basis, Trp absorbs more uv light b. The major contribution to the characteristic absorption of light at 280 nm by proteins is the phenylalanine R group. c. Histidine's ring structure results in its being categorized as aromatic or basic, depending on pH. d. The presence of a ring structure in its R group determines whether an amino acid is aromatic or not. e. All are strongly hydrophilic. 3. For amino acids with neutral R groups, at any pH below the pI of the amino acid, the population of amino acids in solution will: a. have no charged groups b. have no net charge c. have a net positive charge d. have positive and negative charges in equal concentraion e. have a net negative charge 4. A compound has a p K a of 7.4. To 100 mL of a 1.0 M solution of this compound at pH 8.0 is added 30 mL of 1.0 M hydrochloric acid. The resulting solution is pH: a. 7.58 b. 7.4 c. 7.22 d. 6.8 e. 6.53 5. Consider an acetate buffer, initially at the same pH as its p K a (4.76). When sodium hydroxide (NaOH) is mixed with this buffer, the: a. pH remains constant b. pH rises more than when an equal amount of NaOH is added to water at pH 4.76 c. ratio of acetic acid to sodium acetate in the buffer falls d. pH rises more than when an equal amount of NaOH is added to an acetate buffer initially at pH 6.76. 6. The term specific activity differs from the term activity in that specific activity: a. is the activity (enzyme units) in a milligram of protein. b. is the activity (enzyme units) of a specific protein. c. is measured only under optimal conditions. d. refers to proteins other than enzymes. e. refers only to a purified protein. 7. In a mixture of the five proteins listed below, which should elute second in size-exclusion (gel filtration) chromatography? a. cytochrome c , M r = 13,000 b. immunoglobulin G, M r = 145,000 c. ribonuclease A, M r = 13,700 d. RNA polymerase, M r = 450,000 e. serum albumin, M r = 68,500 8. Which of the following describes the overall three-dimensional folding of a polypeptide?
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a. primary structure b. secondary structure c. tertiary structure d. quaternary structure e.none of the above 9. One method used to prevent disulfide bond interference with protein sequencing procedures is: a. cleaving proteins with proteases that specifically recognize disulfide bonds b. protecting the disulfide bridge against spontaneous reduction to cysteinyl sulfhydryl groups. c. removing cystines from protein sequences by proteolytic cleavage.
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Practicetestkey - Practice multiple choice test...

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