DNA & Natural Polymers (AQA GCSE Chemistry)

• Deoxyribonucleic acid (DNA) is a large molecule which is essential to all life
• It contains genetic information which it encodes as instructions which organisms need to develop and function correctly
• DNA consists of four different monomers called nucleotides which contain small molecules called bases and which are abbreviated to A, T, C, and G which are bound together by polymerisation
• The nucleotides form two strands that intertwine, giving the famous double helix shape of DNA
• The bases on either polymer chain pair up in specific sequences forming cross links that hold the strands together, giving rise to the double helix shape
• It is a complex molecule that contains genetic information which is stored in the order in which the bases organise themselves, which is a code for the organisms gene

The double helix

Diagram showing the complex double helix structure of DNA

• Other natural polymers include proteins, starch and cellulose 
• Starch and cellulose are both carbohydrates 
• Starch is used to store energy and cellulose is a stiff polymer used in plant cell walls to provide support
  • Starch and cellulose are both made from the monomer, sugar 
• Proteins are condensation polymers, made from the monomer amino acids 

Natural polymers and their monomers 

Monomer	Natural polymer
amino acids	protein
sugar	starch
sugar	cellulose