This subtopic revisits concepts introduced in Stage 1 subtopics 3.1, 3.2, and 4.2, and in Stage 2 subtopics 3.5 and 3.6.

Proteins are polymers of amino acids.

Amino acids contain a carboxyl group and an amino group.

• Write the general formula of amino acids and recognise their structural formulae.

Video: Proteins (to 5:47)

Amino acids have both acidic and basic properties.

• Draw the structural formula of the product formed when an amino acid self-ionises, given its structural formula.

Video: Flippin' Science (2:10-2:49)

Amino acids can undergo condensation to form protein chains.

The amide groups within proteins are also known as ‘peptide links’.

• Draw the structural formula of a section of a protein chain that could be formed from amino acids, given their structural formulae or vice versa.

Video: Flippin' Science (2:50-5:04)

The unique spatial arrangement of a protein depends on secondary interactions between sections of the chain and, in aqueous environments, between the chain and water.

• Identify where secondary interactions can occur, given the structural formula of a section of a protein chain.

Video: Flippin' Science (6:04-7:00)

The biological function of a protein is a consequence of its spatial arrangement.

• Explain why the biological function of a protein (e.g. an enzyme) may be affected by changes in pH and temperature.

Video: Proteins (from 8:09)

Video: Denaturation and Coagulation

Recipe: Cook without heat - make ceviche