Practice: Predict the predominant form and net charge of tyrosine (Y) at pH 10. What is the net charge?
Amino acids aren't always represented as neutral structures. It's time to represent them appropriately.
At physiological pH (7.4), amino acids exist as zwitterions. Let's take a deeper look.
Concept #1: Why Amino Acids Exist as Zwitterions
Concept #2: Determining Predominant Forms
Concept #3: The 7 Ionizable Amino Acids
As mentioned, 7 of the 20 amino acids have ionizable sidechains. The 7 are: Cysteine (C), Tyrosine (Y), Aspartic Acid (D), Glutamic Acid (E), Lysine (K), Histadine (H), and Arginine (R).
Example #1: Predicting Predominant Form of Lysine
Practice: Determine the net charge of the dipeptide R-C at pH 4.3. (Hint: Peptide bonds do not count)
