CAIE A Level Chemistry 9701 · Nitrogen compounds
The table shows the pKa values for the ionizable groups in glycine and the dipeptide glycylglycine.
| Substance | pKa of | pKa of |
|---|---|---|
| glycine | 2.3 | 9.7 |
| glycylglycine | 3.1 | 8.2 |
Compare the isoelectric points of glycine and glycylglycine, explaining the reasons for any difference.
5 marks, so the mark scheme is looking for about 5 separate creditworthy points. Making the same point twice in different words earns it once.
Compare means: Give similarities or differences between two things, and say which side each point belongs to. Write each point as a pair, for example: A is X, whereas B is Y. Two separate descriptions rarely earn the marks.
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