Chemguide: Support for CIE A level Chemistry


Learning outcome 20.3(b)

This statement is about the way amino acids join up producing peptide bonds. This is only an introduction - the topic is continued in Section 21 of the syllabus.

Before you go on, you should find and read the statement in your copy of the syllabus.


This statement will only be examined in the final exam of a two year course.


You will find what you need on the page about protein structure.

At this stage, you do not need to read the whole of this page. The detailed structure of proteins is covered as a part of Section 21 of the syllabus which you will meet later.

For now, all you need is to go down as far as the second green box.

The syllabus talks about the formation of di- and tri-peptides. The page you have looked at has an example of a dipeptide, and then jumps to a polypeptide containing lots of peptide links.

A tripeptide would look like this, where the R groups can be any combination of same or different:

Notice that a tripeptide has 3 amino acid residues - not three peptide links. Is this confusing? I think so!


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© Jim Clark 2011 (last modified June 2014)