The "boiling" of the peroxide is caused by an organelle in our cells called peroxisomes, which break down toxic peroxide into water and something gas I believe.
The "something" gas is plain old oxygen.
Hydrogen peroxide is basically water with one extra oxygen atom attached: H2O2.
Not the most stable liquid, it doesn't need "special organelles" or anything like that to break it down. Pour some out on a concrete floor from about 3 feet out, and you'll see it fizz as oxygen is released.
It is the pure oxygen that is fatal to bacteria and other microorganisms.
It is the bleaching action of oxygen that makes for all the peroxide blondes with black roots, who try to pass themselves off as the real thing.
Peroxisomes help with the metabolism of fatty acids and are also involved in the breakdown of alkohol in the liver. While it is true that some of them actually produce peroxide, they have nothing whatsoever to do with causing hydrogen peroxide to fizz, when you pour it on a wound.
That concludes todays chemistry lesson!