Acid–Base Properties of Amino Acids Flashcards
Under physiological conditions exists as Zwitterions.
Acid–Base Properties of Amino Acids
An ion with +
(positive) and – (negative) charges on the same molecule with a net zero
charge
Zwitterions
groups that give-up a proton to get negative charge
Carboxyl groups
groups that accept a proton to become positive
Amino groups
In ———–, the NH3 of
the zwitterion loses a proton,
and a negatively charged
species is formed.
basic solution
In basic solution, the ——- of
the zwitterion loses a proton,
and a negatively charged
species is formed.
NH3
In an ——– the
zwitterion accepts a proton
(H+) to form a positively
charged ion.
acidic solution
In an acidic solution, the
zwitterion—— a proton
(H+) to form a positively
charged ion.
accepts
In basic solution, the NH3 of
the zwitterion ——–
a proton,
and a negatively charged
species is formed.
Amino acids in solution exist in three different species
(zwitterions, positive ion, and
negative ion)
shifts with change in pH
Equilibrium
Equilibrium shifts with change in
pH
pH at which the concentration of Zwitterion is maximum
Isoelectric point (pI)
pH at which the concentration of Zwitterion is maximum – net charge
is
zero
Different amino acids have different
isoelectric points
At isoelectric point - amino acids are —— attracted towards an applied electric field
because they carry net zero charge.
NOT attracted
amino acids are NOT attracted towards an applied electric field because they carry net
zero charge
At ————– - amino acids are NOT attracted towards an applied electric field
because they carry net zero charge.
isoelectric point
At pH values lower than pI, the carboxylate end of the zwitterion
picks up a proton from solution, the amino acid acquires a net +
charge, and migrate to the
negative electrode in an electric field.
At ————————, the carboxylate end of the zwitterion
picks up a proton from solution, the amino acid acquires a net +
charge, and migrate to the negative electrode in an electric field.
pH values lower than pI
At pH values higher than pI, a proton is removed from the ———————–,
ammonium
end of the zwitterion
At —————, a proton is removed from the ammonium
end of the zwitterion,
pH values higher than pI
At pH values higher than pI, a proton is removed from the ammonium
end of the zwitterion, the amino acid acquires a
net negative(-) charge
and migrate to the negative electrode
