Peroxisomes: I have learned a few basics about these organelles. They are an old organelle evolutionarily, and the enzymes within have become unique to the organisms, species, and cell types wherein they function.  So in the case of the liver of the mouse, there are going to be many enzymes, but basically for the following purposes: 1) for directing peroxiome-relevant proteins produced by the RER into two places, 1) including the peroxisomal limiting membrane, and 2) the peroxisomal matrix.  Matrix enzymes would include those that are protective, in that they metabolize reactive oxygen molecules, and participate in fatty acid metabolism, and peroxisomal matrix those enzymes that have evolved with the species and its environmental pressures and xenobiotics (which would