Nucleotide Polymers

  • 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 DNA helix is made from two strands of DNA held together by hydrogen bonds, IGCSE & GCSE Biology revision notes

Diagram showing the complex double helix structure of DNA

Starch

  • Carbohydrates are compounds of carbon, hydrogen and oxygen with the general formula Cx(H2O)y
  • There are simple carbohydrates and complex carbohydrates.
  • Simple carbohydrates are called monosaccharides and are sugars such as fructose and glucose.
  • Complex carbohydrates are called polysaccharides such as starch and cellulose.
  • The monomers from which starch and cellulose are made are both sugars.
  • Starch is used to store energy and cellulose is a stiff polymer used in plant cell walls to provide support.
  • Complex carbohydrates are condensation polymers formed from simple sugar monomers and, unlike proteins, are usually made up of the same monomers.
  • A H2O molecule is eliminated when simple sugars polymerise. The linkage formed is an -O- linkage called a glycosidic linkage.

Amylose, IGCSE & GCSE Chemistry revision notes

Diagram of the starch Amylose showing glycosidic linkages (-O-) which bind the monomers together

  • Proteins are also important natural polymers with specific biological functions.
  • Some examples of proteins and their functions include:
    • Haemoglobin which transports oxygen in the blood.
    • Antibodies in the immune system help protect the body from viruses and bacteria.
    • Enzymes which are biological catalysts.

AQA GCSE Chemistry Notes

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Morgan Curtin Chemistry

Author: Morgan

Morgan’s passion for the Periodic Table begun on his 10th birthday when he received his first Chemistry set. After studying the subject at university he went on to become a fully fledged Chemistry teacher, and now works in an international school in Madrid! In his spare time he helps create our fantastic resources to help you ace your exams.