Octanol/Water Partition Coefficient The ratio of the amount of a substance that will dissolve in octanol versus the amount that will dissolve in water.  The higher the octanol/water partition coefficient the greater the tendency of substance to be stored in fatty tissues. Organelle A subcellular structure such as the mitochondria or nucleus of a cell. Oxidation A change in a chemical characterized by the loss of electrons.  This is a primary Phase I type biotransformation reaction.