An enzyme can not be considered a reactant because, like catalysts, the enzyme is never used up in the reaction and is reused again in another chemical reaction. In this lab, the source of hydrogen peroxidase was the potato solution. The substrate that the hydrogen peroxidase acts upon is the hydrogen peroxide. The disks rises to the top of the cup because the substrate, hydrogen peroxide, when sped up by enzyme, creates both water and oxygen as products. The released oxygen is attached onto the disks, allowing it to float to the top of the cup. The way the concentration of enzyme affect the rate of the reaction is because more concentration of enzyme the more active sites are present for the substrate to chemically react with. An enzyme is