Biological molecules and water

Learning objectives

• Connect monomers with their polymers.
• Explain condensation and hydrolysis.
• Relate molecular structure to function.

The big idea

Monosaccharides form polysaccharides, amino acids form polypeptides and nucleotides form nucleic acids. Condensation forms a bond with water produced; hydrolysis uses water to break a bond. Triglycerides contain glycerol and three fatty acids rather than being repeating-unit polymers.

Hydrogen bonding contributes to water’s cohesion and thermal properties. Protein function depends on folding and interactions among side chains; a change in sequence or conditions can alter shape. Cellulose and starch both contain glucose units but differ in linkage and organisation.

Investigate and explain

Using the worked example as supplied data, predict the effect of changing one condition. Draw a labelled model, record your reasoning and identify a variable that would need controlling. No human, animal or microbial experiment is required.

No exact PhET model is claimed for this topic. Use diagrams and supplied-data reasoning instead.

Open the interactive investigation

Check your understanding