Question

pKz Isoelectric point PH PK 2.0 1.0 Equivalents of OH added 3.0
please help me with this

Answer 1

Lysine is an amino acid that contains a carboxylic acid group, the a-amino group, and a second amino group attached to the side chain.

All these groups are protonated at pH=1, where it is very acidic in nature. The net charge in the state of lysine is +2.

When the pH of the solution is raised, by the addition of NaOH, the most acidic site in lysine, the carboxylic acid group will be deprotonated first. The pKa of the CO2H proton is nearly to 2.0. The net charge in this state is +1.

Increases in pH still more by the addition of NaOH will begin to deprotonate aminium group in the lysine, where the pKa nearly to 9.0. The net charge on a lysine in this state is 0.

Further addition of the NaOH will deprotonate the aminium group in the side chain of the lysine. Where the pKa nearly to 10.5. The net charge on a lysine in this state is -1.

H3N-CH-COOⓇ H3N-CH-COOH (CH2) NH3 (CH2) NH3 pH - 2 Lysine at pH = 1 H2N-CH-CO H2N-CH-Coo (CH2)4 (CH2)4 : NH3 NH3 pH = 10.5 pH - 9.0