Joy Paul
Enzyme Catalyst lab
Abstract:
This laboratory explores the affects pH has on a reaction rate. The reaction
studied was the breakdown of hydrogen peroxide catalyzed by the enzyme peroxidase.
Three trials were run at pH levels of 6, 7 and 8. It was hypothesized that the reaction
would run very quickly at a pH of 7, since that is the normal condition of cells where
peroxidase is found. It was further hypothesized that the reaction would slow
significantly at pH’s of 6 and 8 since they are not within the normal pH range of a cell.
All hypotheses were found to be correct. Altering the pH of the solution into which the
enzyme was added slowed the reaction rates significantly. The breakdown of peroxide
occurred most rapidly in the solution with a pH of 7. The slower reaction rates are due to
the addition of hydrogen or hydroxide ions which bond to positively or negatively
charged side chains of the amino acids within the protein. Since the side chains are
bonded to ions in solution, they are unavailable to bond with each other. This lack of
bonding amongst the side chains affects the tertiary structure of the protein, changing its
shape. The shape change makes many of the peroxidase molecules unavailable to
correctly bind with the hydrogen peroxide substrate, thus slowing the rate of the reaction.
Materials and Methods:
Materials:
9 test tubes 4 small beakers One larger beaker with ice
LabPro hardware laptop computer w/ 3 graduated cylinders
Disposable pipette Loggerpro software 30 ml
22
OH
15 ml each of pH buffer 6, 7,8 enzyme source (ground liver)
