Multiple Choice
Electrophoresis separates molecules by migration through a gel only if they have a net charge. How do you expect an amino acid to migrate during electrophoresis when the pH = pI?
3. Amino Acids
Isoelectric Point of Amino Acids with Ionizable R-Groups
Struggling with Biochemistry?
Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
Calculate the pI of Asp.
A
1.4
B
3
C
5.95
D
6.85
Verified step by step guidance1
Identify the ionizable groups in aspartic acid (Asp). Aspartic acid has three ionizable groups: the α-carboxyl group, the α-amino group, and the side chain carboxyl group.
Determine the pKa values for each ionizable group. From the image, the pKa values are: pKa1 (α-carboxyl group) = 2.1, pKa2 (α-amino group) = 9.8, and pKR (side chain carboxyl group) = 3.9.
Understand that the isoelectric point (pI) is the pH at which the molecule carries no net electric charge. For amino acids with acidic side chains like Asp, the pI is calculated using the average of the pKa values of the two acidic groups.
Calculate the pI by averaging the pKa values of the two carboxyl groups: pKa1 and pKR. This is because at the pI, the molecule will be neutral, with the carboxyl groups deprotonated and the amino group protonated.
Use the formula: pI = (pKa1 + pKR) / 2. Substitute the known values: pI = (2.1 + 3.9) / 2. This will give you the pI of aspartic acid.
12:3mWatch next
Master Isoelectric Point Of Amino Acids With Ionizable R-Groups with a bite sized video explanation from Jason
Start learningRelated Videos
Related Practice
Isoelectric Point of Amino Acids with Ionizable R-Groups practice set
Problem sets built by lead tutorsExpert video explanations