Exam 24: Amino Acids, Peptides, and Proteins

Which of the following amino acids are classified as essential amino acids? (More than one answer is possible.)

Which of the following fragments would not result when the decapeptide Asn-Gly-Lys-Phe-Pro-Arg-Gly-Leu-Lys-Ser is treated with trypsin?

Which of the following amino acids does not have an aromatic substructure within its side chain?

Provide a detailed, stepwise mechanism for the Strecker synthesis of racemic alanine from acetaldehyde.

Provide a structure of the dipeptide Ala-Ser.

Bradykinin is a nonapeptide released by globulins in the blood in response to a wasp sting. Hydrolysis gives the following amino acids: 2 Arg, Gly, 2 Phe, 3 Pro, and Ser. Edman degradation gives phenylthiohydantoin of Arg. Cleavage with carboxypeptidase gives Arg. Partial hydrolysis gives the following di- and tripeptides: Phe-Ser, Pro-Gly-Phe, Pro-Pro, Ser-Pro-Phe, Phe-Arg, and Arg-Pro. What is the amino acid sequence of bradykinin?

Provide a reasonable synthesis of racemic alanine from ethanol.

A student proposed to make aspartic acid from succinic acid using Br₂/PBr₃, then adding a large excess of NH₃. Why might this synthesis not work?

How would you make tryptophan using the Strecker Synthesis?

Which of the following compounds would reduce a disulfide linkage in a peptide?

What is the major force responsible for the formation of an α-helix in protein secondary structure?

Given the following pKa values, what is the major ionization state of histidine at pH 11? (α-COOH = 2.0, α-NH₃⁺ = 9.0 and R-group imine = 6.5)

Which of the following arrangements is usually not found in the secondary structure of proteins?

Provide the structure of the predominant form of L-methionine present in an aqueous solution at biological pH, pH = 7.4.

How many standard amino acids are there?

Amino acids have ________.

Provide the structure of the predominant form of alanine present in an aqueous solution at a pH of 2.0.

Treatment of a peptide which contains disulfide linkages with peroxyformic acid yields a peptide which contains what new amino acid residue?

Which method gives you information about the N-terminus end of a peptide?

Give a detailed, stepwise mechanism for the formation of the activated acyl derivative from the reaction of an amino acid with N,N'-dicyclohexylcarbodiimide.