Practice MT Ans

Note because of the chemical similarities between leu

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Unformatted text preview: u and Ile the solvent is not an issue Question #8 (9 points) The hydrophobic effect refers to the stabilization of protein structure due to H-bonds between the hydrophobic side chains of amino acyl residues. True (T) or False (F)? F During polypeptide folding, the number of H-bonds formed is much larger than than the number broken. F As compared to the unfolded state, folded state of a polypeptide is highly stable one. F β-mercaptoethanol denatures proteins by disrupting internal H-bonds. F Anionic detergents are expected to be more effective denaturants than uncharged ones. T Motionally restricted water molecules surrounding oligomeric proteins stabilizes their oligomeric structure. F When a polypeptide folds, most hydrophilic groups of the peptide linkage maintain H-bonds with water. F A polypeptide folds spontaneously with a ∆HFOLD = O This means that T∆SWATER must be > T∆SPOLY . T A protein with a low % content of α-helix tends to possess a high % content of β-sheet T Question #9 (8 points) The diagram below is a 37 amino acid alpha-helical blood protein synthesized by polar fish known as the winter flounder. The protein is a biological “antifreeze”. It inhibits ice crystal formation and helps to keep the fish’s serum liquid below 0oC. (a) Estimate ∆HH-bond /mol for the folding of the protein in water. Consider only H-bonds involving the peptide linkages of the polypeptide backbone. That is, ignore anything to do with R-groups (amino acid side chains) and the N and C termini. Before doing the calculation note the following assumptions! ASSUME (1) the energy (at 25oC/1 atm) required to break a H-bond between C=O and H-N in an α-helix = 15 kJ/mol. (2) the energy (at 25oC/1 atm) required to break a H-bond involving H2O = 12 kJ/mol. (3) that all H-bond acceptor atoms accept only one H-bond. (4) the 4 “unsatisfied” backbone C=O and N-H groups maintain their H-bonds with water in the folded state. This is IMPORTANT! For FULL credit, you must CLEARLY i...
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