These chemicals, peroxides and free radicals, can serve as promoters in the tissue because they cause mutations and damage membranes and proteins in the cell too. A molecule with an unpaired electron. This makes it very reactive. Water is an example of a molecule where all the electrons are paired. The OH free radical has a single unpaired electron.
Peroxides frequently react to form free radicals.
A. Testing chemicals to see if they're bad. Test developed by Bruce Ames. If a chemical mutates DNA in bacteria, it can cause cancer. Chemical is put on a culture dish with the bacteria, and you wait to see if the bacteria get any mutations. Liver enzymes can convert a chemical that is OK to a carcinogen.