T-Mobile 2:58 PM Lehninger Principles of Biochemistry Collapse all Share Step 1
ID: 566263 • Letter: T
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T-Mobile 2:58 PM Lehninger Principles of Biochemistry Collapse all Share Step 1 (a) The structure of â â is represented as NH3 group associated with PA, is the carboxyl The functional group which has the value 3.39 and the functional group associated with pK is the amino g is the amino group with the value 8.03 Step 2 (b) The value of P ncreases with the addition of each alanine residue because of the electrostatic interaction between the negative charge of the carboxyl group and the positive charge of the amino group of alanineâs zwitter ion which favorably effects the ionization of carboxyl group This electrostatic interaction decreases, as the length of the oligopeptide (here it is oligo Alanine) increases which ultimately results in increase in the i Chapter 3 Problem 7PExplanation / Answer
(a) structure of "a" (a peptide) is given above
addition of more alanine to the chain increase the pK1 value.
pK1 and K1 are inversely proportional. So an increase in pK1 means decrease in acidity of the -COOH group.
pK1 = -log[K1]
So, by adding alanine units to the chain, the electron donating alkyl chain makes the -COOH proton less electropositive in nature and thus less ionizable as compared to a lone alanine unit. The alkyl chain exerts an electron donating inductive effect on the -COOH group, making it less acidic (high pK1).
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