Lecture 4: Amino Acid Properties

Question 1

pKas of amino acids

Answer 1

• At physiological pH(7.4), carboxyl group is deprotonated and amino group is protonated
• pKa < pH = deprotonated

Question 2

Zwitterion

Answer 2

• Neutral molecule that has a separate positively and negatively charged functional groups
• When R group is uncharged, free amino acids can be zwitterions
• Not all amino acids are zwitterions

Question 3

Titration

Answer 3

• Three buffering regions exist around the three pKa values
• Isoelectric point(pI) is pH when the charge of the molecule is zero