Problem 2
RECALL Which amino acid is technically not an amino acid? Which amino acid contains no chiral carbon atoms?
Problem 3
RECALL For each of the following, name an amino acid in which the \(\mathrm{R}\) group contains it: a hydroxyl group, a sulfur atom, a second chiral carbon atom, an amino group, an amide group, an acid group, an aromatic ring, and a branched side chain.
Problem 4
RECALL Identify the polar amino acids, the aromatic amino acids, and the sulfur-containing amino acids, given a peptide with the following amino acid sequence: Val-Met-Ser-Ile-Phe-Arg-Cys-Tyr-Leu
Problem 5
RECALL Identify the nonpolar amino acids and the acidic amino acids in the following peptide: Glu-Thr-Val-Asp-Ile-Ser-Ala
Problem 6
RECALL Are amino acids other than the usual 20 amino acids found in proteins? If so, how are such amino acids incorporated into proteins? Give an example of such an amino acid and a protein in which it occurs.
Problem 13
MATHEMATICAL An organic chemist is generally happy with \(95 \%\) yields. If you synthesized a polypeptide and realized a \(95 \%\) yield with each amino acid residue added, what would be your overall yield after adding 10 residues (to the first amino acid)? After adding 50 residues? After 100 residues? Would these low yields be biochemically "satisfactory"? How are low yields avoided, biochemically?
Problem 15
REFLECT AND APPLY Suggest a reason why amino acids are usually more soluble at \(\mathrm{pH}\) extremes than they are at neutral pH. (Note that this does not mean that they are insoluble at neutral pH.)
Problem 18
REFLECT AND APPLY If you were to have a mythical amino acid based on glutamic acid, but one in which the hydrogen that is attached to the \(\gamma\) -carbon were replaced by another amino group, what would be the predominant form of this amino acid at \(\mathrm{pH} 4\) \(7,\) and \(10,\) if the \(p K_{a}\) value were 10 for the unique amino group?
Problem 21
REFLECT AND APPLY Consider the following peptides: Phe- GluSer-Met and Val- Trp-Cys-Leu. Do these peptides have different net charges at \(\mathrm{pH} 1\) ? At \(\mathrm{pH} 7\) ? Indicate the charges at both \(\mathrm{pH}\) values.
Problem 22
REFLECT AND APPLY In each of the following two groups of amino acids, which amino acid would be the easiest to distinguish from the other two amino acids in the group, based on a titration? (a) gly, leu, lys (b) \(\mathrm{glu},\) asp, ser
