# Protonation & Deprotonation

 when protonated have a formal charge of 0 & when deprotonated have a formal charge of -1 CDESTY side chains & carboxylate (Cysteine has an S & all the other ones have an O.) when protonated have a formal charge of +1 & when deprotonated have a formal charge of 0 HKR (Histidine, Lysine, Arginine) side chains & amino (They all have N. Remember that NQ are NOT ionizable.) Calculate the charge on a fully protonated non-ionizable free amino acid NH3+: +1COOH: 0R: N/ATotal charge = +1 (non-ionizable amino acids: all hydrophobic + NQ) Calculate the charge on a fully deprotonated non-ionizable free amino acid NH2: 0COO-: -1R: N/ATotal charge = -1 (non-ionizable amino acids: all hydrophobic + NQ) Calculate the charge on a fully protonated CDESTY free amino acid NH3+: +1COOH: 0R: 0Total charge = +1 Calculate the charge on a fully deprotonated CDESTY free amino acid NH2: 0COO-: -1R: -1Total charge = -2 Calculate the charge on a fully protonated HKR free amino acid NH3+: +1COOH: 0R: +1Total charge: +2 Calculate the charge on a fully deprotonated HKR free amino acid NH2: 0COO-: -1R: 0Total charge = -1 Which amino acids do NOT exist as a zwitterion at a pH of 7.40? DEKR DE will have an overall charge of -1KR will have an overall charge of +1 zwitterion: sum of formal charges in a molecule is 0 (the neutral state). All the other 16 amino acids will have a charge of 0 at a pH of 7.40 Determine the protonated:deprotonated ratios of each ionizable functional group for the free amino acid Lysine. pH is set to 7.40.If pH > pKa, expect more deprotonated.If pH < pKa, expect more protonated.Add exponent value |pH-pKa| to the 10. alpha COO- pKa = 2.20. pH > pKa. 1:10^5.2 (prot:deprot) alpha NH3+ pKa = 9.40. pH < pKa. 10^2:1 (prot:deprot) Lys R group pKa = 10.50. pH < pKa. 10^3.1:1 (prot:deprot) Authorsophathida ID350541 Card SetProtonation & Deprotonation DescriptionProtonated, deprotonated Updated2020-02-06T17:13:40Z Show Answers