Lecture 4 Amino Acid Properties Flashcards
What are non-covalent interactions?
Non-covalent interactions include hydrogen bonds, ionic bonds, Vanderwal, and hydrophobic interactions
How do you predict the charge of an amino acid at a given pH?
Compare the pKa of the amino acid to the given pH and decide if it’s protonated or deprotonated
At physiological pH 7.4, what is the deprotonation and protonation of the carboxyl group and the amino group like?
The carboxyl group is the deprotonated COO- and the amino group is protonated NH3+
What is a Zwitterion?
A molecule with both positive and negative charges, but within with an overall neutral charge
When do amino acids become Zwitterions?
Amino acids with charged R groups can becomes Zwitterions at certain pH levels, especially near their isoelectric point
What is the pI?
pI is the pH when the net charge of an amino acid is zero
How do you calculate the Isoelectric point?
pI=pk2+pk3/2
How do you calculate the charge of a polypeptide at a given pH?
Add the charges of each amino acid side chain, N terminus and C terminus
What happens to a protein at pH 7 when its pI is 9 and why?
Since the pH is less than the pI, the protein will be positively charged because there’s more protons
Why do amino acids act as buffers?
Amino acids can accept and donate protons at different pH levels
where do buffering regions occur?
buffering regions occur around the pKa values of their ionizable groups
