Consider the tripeptide tyrosylleucylisoleucine. a. Specify its structure using three-letter symbols for the amino acids. b. How many peptide bonds are present within the peptide? c. Which of the amino acid residues has the largest R group? d. Which of the amino acid residues, if any, has an acidic side chain?

22-44 How can a protein act as a buffer?

22-89 What kind of noncovalent interaction occurs between the following amino acids? (a) Valine and isoleucine (b) Glutamic acid and lysine (c) Tyrosine and threonine (d) Alanine and alanine

To which family of mirror-image isomers do nearly all naturally occurring amino acids belong?

22-49 Based on your knowledge of the chemical properties of amino acid side chains, suggest a substitution for leucine in the primary structure of a protein that would probably not change the character of the protein very much.

For the tripeptide SerArgIle which amino acid residues a. are hydrophilic b. are hydrophobic c. possess polar neutral R groups d. participate in two amide linkages

22-84 How many different dipeptides can be made (a) using only alanine, tryptophan, glutamic acid, and arginine and (b) using all 20 amino acids?

22-9 What is the difference in structure between tyrosine and phenylalanine?

What characteristics indicate that amino acids exist as zwitterions?