3.3.13.1 Amino acids

Amino acids have both acidic and basic properties, including the formation of zwitterions.

Students should be able to draw the structures of amino acids as zwitterions and the ions formed from amino acids:

• in acid solution

• in alkaline solution.

3.3.13.2 Proteins

Proteins are sequences of amino acids joined by peptide links.

The importance of hydrogen bonding and sulfur–sulphur bonds in proteins.

The primary, secondary (α-helix and β–pleated sheets) and tertiary structure of proteins.

Hydrolysis of the peptide link produces the constituent amino acids.

Amino acids can be separated and identified by thin-layer chromatography.

Amino acids can be located on a chromatogram using developing agents such as ninhydrin or ultraviolet light and identified by their Rf values.

Students should be able to:

• draw the structure of a peptide formed from up to three amino acids

• draw the structure of the amino acids formed by hydrolysis of a peptide

• identify primary, secondary and tertiary structures in diagrams

• explain how these structures are maintained by hydrogen bonding and S–S bonds