Glutamic acid, `H_2NCH(CH_2CH_2COOH).COOH` has `Pk_alpha,(alpha-COOH) =22,Pk_(alpha_2) (alpha -overset+ NH_3)=9.8`and `pK_(alpha_3)`(R group COOH)=4.3. The isoelectric point of glutamic acid is

Options

A. `5.9`
B. `7.0`
C. `10.2`
D. `3.2`

Answer

D

Explanation

`{:(H_(3)overset(+)-CH-COOH),(" "|),(" "CH_(2)CH_(2)COOH),(" ""Cationic form"):} overset("On neutralization")underset("1st ionization")to`
`{:(H_(3)overset(+)N-CH-COO^(-)),(" "|),(" "CH_(2)CH_(2)COOH):}`
`underset("2 nd ionization")to {:(H_(3)overset(+)-CH-COO^(-)),(" "|),(" "CH_(2)CH_(2)COO^(-)):}`
Isoelectric point `(pI)=(pK_(a_(1))+pK_(a_(2)))/(2)=(2.2+4.3)/(2)=3.25`