Most of us like being out in the Sun, but we’ve also all heard to be careful not to get sunburned since too much sun can cause serious problems like skin cancer, along with less serious problems like wrinkles and dry skin. The Sun can damage your skin because the ultraviolet rays from the Sun are relatively high-energy photons that can damage the elastin fibers in your skin. These can then lose their ability to go back to their original position after they are stretched and also lose their ability to heal as quickly when wounded or bruised.

As we discussed briefly in “Biochemistry,” the cause of cancers generally involve damage to the genetic material (DNA) of your cells, which interferes with their ability to replicate (or stop replicating) normally. With regard to cancers arising from too much exposure to ultraviolet radiation, DNA can be damaged in two ways. The first, probably more obvious, route is that the ultraviolet radiation could be absorbed by the DNA directly, causing changes in its chemical structure. The second possibility is that ultraviolet radiation can be absorbed by other molecules first, forming reactive, damaging radical species (like hydroxyl radicals or singlet oxygen), which then diffuse through cells and can damage DNA.