biology molecular L1 (monomers and polymers)

Monomer

A smaller unit from which larger molecules are made

Polymer

A molecule made from a large number of monomers joined together, usually via a repeating process called polymerisation

Examples of monomers

Monosaccharides, amino acids and nucleotides

Condensation reaction

A reaction that joins two molecules together with the formation of a chemical bond, and involves the elimination (removal) of a water molecule

Hydrolysis reaction

A reaction that breaks a chemical bond between two molecules, and involves the use (addition) of a water molecule

Why organic compounds like carbohydrates, proteins, lipids and nucleic acids are classed together*

They all contain the elements carbon and hydrogen

Macromolecule

A very large molecule, containing 1000 or more atoms and therefore a high molecular mass

Are all macromolecules polymers?*

No — polymers must be made of repeating identical/similar subunits, but not all macromolecules have this repeating structure (e.g. some large molecules are not built from one repeating monomer)

Explain what is meant by the term 'polymer', using an example (2 marks)

A polymer is a molecule made from a large number of monomers joined together [1]; example: a polysaccharide is a polymer of monosaccharide monomers, or a polypeptide is a polymer of amino acid monomers [1]

State two examples of monomers and name the polymer each forms (2 marks)

Monosaccharides form polysaccharides [1]; amino acids form polypeptides / nucleotides form polynucleotides (DNA/RNA) [1]

Describe what happens during a condensation reaction between two monomers (3 marks)

Two molecules join together [1]; a chemical bond forms between them [1]; a molecule of water is eliminated/released [1]

Explain the difference between a condensation reaction and a hydrolysis reaction (2 marks)

Condensation reaction joins molecules together and releases/eliminates water [1]; hydrolysis reaction breaks a bond between molecules and requires/adds a water molecule [1]

A student breaks down a disaccharide into two monosaccharides. Name the type of reaction involved and state what is used in the reaction (2 marks)

Hydrolysis reaction [1]; water is added/used to break the glycosidic bond [1]

[Analogy] Monomers and polymers

Monomers are like individual LEGO bricks; a polymer is the whole model built by clicking many bricks together in a chain. (Intuition aid only — do not write this in an exam answer, use the proper terms)

[Analogy] Condensation vs hydrolysis

Condensation = clicking two LEGO bricks together (and a tiny bit gets 'squeezed out' — that's the water molecule released). Hydrolysis = pulling two bricks apart, but you have to add a drop of water first to make them come apart. (Intuition aid only — use proper terms in exams)