Biological polymers

Biological polymers are made naturally by living organisms.


DNA is a polymer made from four different monomers, called nucleotides. These join together in different combinations to make long strands. In a DNA molecule, two strands wrap around each other to form a double helix structure.

DNA strand showing bases pairs: TA, GC, AT repeated randomly.A simple model of DNA (deoxyribonucleic acid)

There are four different nucleotides:

  • adenine, A
  • thymine, T
  • cytosine, C
  • guanine, G

Intermolecular forces between nucleotides on opposite strands hold the structure of DNA together.


Starch is a polymer made from sugar monomers. Starch molecules contain many glucose molecules, joined together in long chains with branches.

A single glucose molecule and several glucose moleceules attached together, which make starchA simple model of starch


Proteins are polymers made from different monomers, called amino acids. These join together in different combinations to make long strands, which then fold into complex shapes

The covalent structures of glycine and alanine.Two different amino acids

Name the monomers found in DNA, starch and proteins.

Nucleotides are the monomers for DNA, glucose is the monomer for starch, and amino acids are the monomers for proteins.