CHEM 3050 Lecture Notes - Lecture 30: Scissile Bond, Enzyme Catalysis, Tetrahedral Carbonyl Addition Compound

first step last step His 57 donates H to N of scissile peptide bond tetrahedral intermediate collapses water donates H to ring N of His 57 His 57 donates H to Ser 195 0 tetrahedral intermediate collapses His 57 ring N deprotonates Ser 195 hydroxyl hydroxide ion attacks carbonyl of remaining N-terminal piece of substrate the C-terminal piece of peptide substrate (with new amino terminus) diffuses away nucleophilic Ser 195 O- attacks carbonyl C of substrate N-terminal piece of peptide substrate (with new carboxyl terminus) diffuses away

34. Which of the following amino acids can coordinate to a metal ion? a. arginineb. glutamic acid c. isoleucine d. phenylalanine 35. Which of the following denaturing agents affects hydrophobic regions? a. detergents c. heavy metals b. heat d. urea 36. Which of the following pairs of amino acid s can form hydrogen bonds? a. alanine and glutamic acid c. leucine and phenylalanine b. aspartic acid and lysine d. serine and tyrosine 37. How many amino acids have an amide side chain? c. 3 d.4 38. Which of the following is true of the isoelectric point of amino acids? a. The isoelectric points of all amino acids are the same. b. It is the pH at which an amino acid conducts electricity c. It is the pH at which an amino acid has equal numbers of positive and negative charges. d. All of the above are true 39. Antiparallel β-sheets have t progress from N to C termini in the same direction. a. sheets that b. usually all of their hydrophobic residues on one side of the sheet. c. all hydrophobic residues. d. all hydrophilic residues e. fibers that can be stretched or extended, but are not flexible 40. Alpha helices are stabilized primarily by: a. hydrogen bonds between the main chain peptide bond component atoms. b. electrostatic interactions between R-groups c, hydrophobic interactions between the α-carbons of the main chain. d. hydrogen bonding between the R-groups. e. hydrophobic interactions between R -groups and the solvent water . An electrostatic interaction might occur within a protein between which of the following amino acid pairs at typical physiological pH? a. Ser/Asın b. Asp/Glu c. Arg/Cys d. Lys/Asp e. Val/lle