How do amino acids change at different pH?

Amino acids are amphoteric which means they can act as an acid or a base.

An isoelectric point is the pH at which an amino acid exists as its zwitterion. A zwitterion is the dipolar ionic form of an amino acid. This is formed by a hydrogen ion (H+) from the carboxyl group being donated to the amino group. There is no overall charge. The carboxyl group becomes COO- and the amino group becomes NH3+ showing an imbalance of charge that makes it a polar molecule.

If the pH is lower (in acidic conditions) than the isoelectric point then the amino acid acts as a base and accepts a proton at the amino group. This gives it a positive change.

If the pH is higher (in alkaline conditions) than the isoelectric point then the amino acid acts as an acid and donates a proton from its carboxyl group. This gives it a negative charge.

ZC
Answered by Zoe C. Chemistry tutor

72637 Views

See similar Chemistry A Level tutors

Related Chemistry A Level answers

All answers ▸

But-1-ene reacts with HBr to form a saturated compound, name and draw the mechanism, then explain how three isomeric products are formed.


Explain why the atomic radii of the elements decrease across Period 3 from sodium to chlorine


Excess KCN(aq) is added to a solution of [Co(H2O)6]2+. Identify the complex ion formed and predict its shape and charge.


Calculate the empirical and molecular formula of unknown compound A which gave an m/z of 181 in the mass spectrum for the molecular ion peak. Elemental analysis by combustion shows the compound is C 53%, O 35.4%, H 3.9% and N 7.7%.


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences