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3 - Surname Given name Number p 4 15 A polypeptide contains...

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Unformatted text preview: Surname: Given name: Number: p. 4 15. A polypeptide contains three lysine residues. Treatment of the peptide with the enzyme trypsin (which cleaves after lysine or arginine residues) produces four fragments (oligopeptides or amino acids). We can conclude that - A) the C-terminal residue was lysine; (3 Q ;@f x: B) the C-terminal residue was either lysine or arginine; . C) the polypeptide did not contain any arginine residues; D) if the polypeptide contained an arginine residue, it was at the C-terrninus; 7 ‘ ; E) none of the above conclusions is justified. ' i I 7 it 3:15, a; .3 16. In determining the primary sequence of insulin, in the 19505, Frederick Sanger used l-fluor0-2,4- dinitrobenzene (FDNB) as an electrophilic reagent for labeling theNH2 termini of peptide fragments. Biochemists would not use this method today, because: A) the Edman reagent, PITC, provides much more useful sequencing results; B) the development of NMR (nuclear magnetic resonance) methods has made chemical sequencing of proteins obsolete; C) the toxicity of FDNB (not known to Sanger) renders its laboratory use unacceptable; D) recombinant DNA technology has made the chemical sequencing of proteins obsolete; E) all of the above statements are correct. 17. At each step, during a step-wise enzyme purification procedure, we measure: i) the total amount of protein (in mg); ii) the-total enzyme activity (in activity units); and we calculate iii) the specific enzyme activity (in units per mg). At each step, these three quantities will usually... A) i) decrease, ii) increase, iii).increase; l . l . B) i) decrease, ii) remain constant, iii) remain constant; A r_ ' . f=l _/ a» " " C) i) increase, ii) increase, iii) increase; , i \ 9;: ' ’ : ll fl l ../' D) i) decrease, ii) decrease, iii) increase; l 0 '2 k" - ”17 l ,1" E) i) remain constant, ii) increase, iii) increase. ,I l / 18. The tertiary structure of the enzyme hexola'nase is significantly altered in the presence of glucose. . This phenomenon illustrates the principle of: iii A) irreversible inhibition; B) homeostasis; C) ”induced-fit"; D) "lock-and-key" specificity; E) negative feedback. 19. Which one of the following is n_ot among the six major classes of enzymes? A) hydrolases; B) ligases; C) lyases; D) polymerases; E) transferases. ...
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