Concept check question

Consider glutamate in its fully protonated form $($e$.$g$.$ in a pH $=1$ solution$)$

$pK{a}_{\text{c}\text{a}\text{r}\text{b}\text{o}\text{x}\text{y}\text{l}}=2\mathrm{.}19$

$pK{a}_{\text{a}\text{m}\text{i}\text{n}\text{o}}=9\mathrm{.}67$

$pK{a}_{\text{s}\text{i}\text{d}\text{e}\text{c}\text{h}\text{a}\text{i}\text{n}}=4\mathrm{.}25$

Draw all the forms of glutamate at various $pH$

Calculate the $pl$ of this amino acid

Sketch a titration curve showing $pH$ as a function

of added $O{H}^{-}$and locate the predominant forms

of histidine in the curve

STEPS:

Find the $H$ atoms that can be removed on the molecule

Associated a pKa value to each removable $H.$

Draw the Aa structure at:

i$)pK{a}_2$

Indicate the net charge $of$ each structure

Calculate the $pl$ with the pKa's that bracket the neutral form $of$ glutamate.

Sketch a titration curve and locate the dominant forms $of$ glutamate $on$ the $curvepK{a}_R$

$ivpK{a}_1$

iiipH

$ii$