Dear Sir,

My name is Dor, and I am studying biology in the high school. 
My friends and I have a question:
How does Hydrogen peroxide (H2O2) enter the cell? I know that water(H2O) can enter the cell through the aquaporins – the water channels in the membrane. So maybe the Hydrogen peroxide (H2O2) can break into OH- ions which dissolve in the water? Or maybe can it just generate hydrogen bands with the water molecules, and get through the aquaporins as a single molcelue(H2O2)?

Sincerely,
Dor

Updated answer:

The majority of intracellular H2O2 is generated within the cell and there is only limited passive diffusion across the lipid bilayer of mammalian cell membranes. There is limited evidence to indicate that some of the aquaporins could actively transport H2O2 across the cell membrane as well as water in mammals. In contrast, that definately does occur in plants.

For more details see:-
Biochimica et Biophysica Acta (BBA) - Biomembranes
Volume 1758, Issue 8, August 2006, Pages 994-1003