title: Heme O
text: # Heme O
  
  Heme O (or haem O) differs from the closely related heme A by having a methyl group at ring position 8 instead of the formyl group. The isoprenoid chain at position 2 is the same.
  
  Heme O, found in the bacterium Escherichia coli, functions in a similar manner to heme A in mammalian oxygen reduction.
  
  