Is serine chiral? Draw serine and identify the chiral atom. Explain why serine is chiral.

Threonine has two chiral centers. Draw L-threonine and indicate which carbon atoms are chiral. Which carbon atom is responsible for D and L configuration?

Draw leucine and identify any chiral carbon atoms with arrows.

Identify some differences between the following pairs:

b. complete and incomplete proteins

Glycine has the zwitterion structure shown. Draw the structure and give the net charge of glycine that will predominate at the indicated pH values (pI = 6.0).

a. pH 1.5

Two of the 20 common amino acids have two chiral carbon atoms in their structures. Identify these amino acids and their chiral carbon atoms.

Which would you expect to be more soluble in water, a peptide containing mostly alanine and leucine or a peptide containing mostly lysine and aspartic acid? Explain. (Hint: Consider side-chain interactions with water.)

What kind of biological function would each of the following proteins perform?

c. Protease