Problem Set 5

1.  Serine has pKa's of 2.21 and 9.15.

   a.  Draw the three forms of serine that could be present at various pH's.  Show all bonds, atoms, and charges.

   b.  Draw the structure of serine that is most prevalent at physiological pH.

  c.  Draw the  structure of serine that would be prevalent for a pH range of 1-2 (stomach).

   d.  For a pH of 10.15, draw and calculate the ratio of the two most prevalent forms of serine.

2.  Lysine has pKa's of 2.18, 8.95, and 10.53 (side chain).

   a.  Draw the structure of lysine that is most prevalent at physiological pH.

   b.  Draw and calculate the ratio of the two most prevalent forms of lysine at a pH of 4.0.