4.3 - Naturally Occurring Polymers

DNA, a natural polymer

DNA (deoxyribonucleic acid) is a naturally occurring polymer found in every living thing and many viruses, and is essential for life.

Structure of DNA

• DNA is built from monomers called nucleotides, and there are four different ones.
• A DNA molecule consists of two polymer chains held together and twisted into a double helix.
• The order of the nucleotides along the chain acts as a code that holds genetic instructions for how a living thing develops and functions.
• A short length of chain carrying one of these instructions is called a gene.

Starch, cellulose and proteins

Polymers built from sugars

• Sugars are small molecules made of carbon, hydrogen, and oxygen.
• Sugars are carbohydrates, and so are the polymers built by joining many sugar molecules end to end, including:
  • Starch - Used by living things to store energy.
  • Cellulose - Used to build plant cell walls, giving plants strength and structure.

Polymers built from amino acids

• Amino acids are small molecules that join end to end to form proteins.
• Joining different amino acids in different orders produces many different proteins, which carry out a wide range of functions in living things.