Chapter 3: Amino Acids, Peptides, Proteins. HLY-JU-JS-CD. Amino Acids (AA) are the building blocks of peptides and proteins. Peptides generally contain 2-10 AA Polypeptides contain 10-100 AA Proteins contain >100 AA General structure of AA: at pH ~7.4:.
General structure of AA:
at pH ~7.4:
*Histidine is basic but uncharged
See structures on page 70 of your book.
Isoelectric point (pI) of an AA (or peptide/protein) is equal to the pH when net charge = 0
pK1: -COOH -COO- + H+
pK2: -NH3+ -NH2 + H+
pKR: -RH -R- + H+
Case II: MORE THAN TWO IONIZABLE GROUPS.
Ex. Aspartic Acid
Thrombin and Fibrinogen