`alpha` - amino acids are high melting crystalline solids because of the zwitterion structure. They are moderately soluble in water. In acidic medium, `alpha` - amino acids exist as cations (I) and thus migrate towards cathode under the influence of an electric field. On the other hand, in alkaline medium, `alpha` - amino acids exist as anions (III) and thus migrate towards anode under the influence of an electric field. However, at some intermediate value of `p^(H)`, the concentration of the cationic form (I) and anionic form (III) will become equal and consequently the `alpha` - amino acid will exist primarily as the neutral dipolar ion (II). At this `p^(H)`, there would be no net migration of the amino acid in an electric field. This `p^(H)` at which there is no net migration of the amino acid under the influence of an applied electric field is called isoelectric point (pI). Each amino acid has a characteristic isoelectric point. The pH of an amino acid that does not have an ionisable side chain such as alanine isd average of `pK_(a)` values of the carboxyl group and the protonated amino group.
`H_(3)overset(+)(N)-overset("R")overset("|")("C")H-COOH overset(" "OH^(-)" ")underset(" "H^(+)" ")hArr H_(3)overset(+)(N)-underset("Zwitterion (II)")(overset("R")overset("|")("C")H)-COO^(-)overset(" "OH^(-)" ")underset(" "H^(+)" ")hArr underset((III))(overset(+)(N)-overset("R")overset("|")("C")H)-COO^(-)`
Further, the `alpha` - carbon of all the amino acids (except glycine) is chiral (asymmetric) and hence amino acids can exist in teo stereoisomeric forms i.e., D and L. However, all the nautrally occurring amino acids belong to the L - series.
`underset("L(-)Glyceraldehyde")(HO-overset("CHO ")overset("| ")underset(" "CH_(2)OH)underset("| ")("C ")-H)" " underset("L-Amino acid")(H_(2)N-overset("COOH")overset("| ")underset("R ")underset("| ")("C ")-H)`
N - terminus of the peptide structure is on the

Options

A. `H_(3)overset(o+)(N)CH_(2)CH_(2)CH_(2)CH_(2)underset(o+NH_(3))underset("|")("C")HCO_(2)H`
B. `H_(3)overset(o+)(N)CH_(2)CH_(2)CH_(2)underset(NH_(3))underset("| ")("C ")HCO_(2)^(Θ)`
C. `H_(2)NCH_(2)CH_(2)CH_(2)CH_(2)underset(NH_(2))underset("| ")("C ")HCO_(2)^(Θ)`
D. `H_(2)NCH_(2)CH_(2)CH_(2)CH_(2)underset(NH_(2))underset("| ")("C ")HCOOH`

Answer

C

Explanation

Lysine PI = 9.74, of PH `gt` PI it exist as anion.