Final answer:
The isoelectric point (pI) of an amino acid like glycine, which does not have a charged side chain, is calculated as the average of the pKa values for its amino and carboxyl groups, typically falling within a range of 5.0 to 6.5.
Step-by-step explanation:
To find the isoelectric point (pI) of an amino acid, like glycine, which does not have a pKa for its side chain, you must consider the pKa values of the amino and carboxyl groups. The pI of an amino acid is the pH at which the molecule carries no net electric charge. For amino acids with no charged side chain, the pI is calculated as the average of the pKa values for the amino and carboxyl groups.
Glycine, being the simplest amino acid with no side chain pKa, has a pI between its two relevant pKa values: the alpha carboxyl group (pK1) and the alpha amino group (pK2). For glycine, this would be approximately (pK1 + pK2) / 2.
Since glycine's side chain is neutral, its isoelectric point typically falls in the range of 5.0 to 6.5, which is average for amino acids without charged side chains.