Does Manipulation of Substrate Ph Affect Enzymatic Catalysis?

Does Manipulation of Substrate pH Affect Enzymatic Catalysis?

Introduction:

An enzyme is a protein that reduces the activation energy required by reactant molecules (called substrates) without requirement of an external energy source. The structure of the enzyme remains unchanged, therefore permitting them to participate in multiple chemical reactions. "An enzyme promotes the formation of bonds between separate substrates, or induces the breaking of bonds in a single substrate to form the product or products of the reaction…each enzyme has an optimum temperature and pH at which it functions most efficiently" (Hillis, et.al 2011). The enzyme catalase, introduced in this lab, plays an important function in the cells of almost all aerobic organisms to break down harmful levels of hydrogen peroxide, (a by-product of oxygen metabolism) into harmless and useful products - oxygen and water. This experiment manipulates the pH of a substrate (H2O2) to observe if the alteration of the substrate pH does denature the structure of the protein enzyme, catalase, thereby inhibiting the enzyme's ability to perform catalysis of the substrate. The measurement of the enzyme reaction rate is measured indirectly by the accumulation of O2 (g) over time.

Hypothesis:

The enzyme catalase will not be able to catalyze the substrate H2O2 when substrate pH balances are manipulated outside of enzyme optimal pH range due to denaturation of enzyme protein. The rate of catalysis will be evidenced by the production of O2 (g) over time.

Materials & Methods:

The control group (CG) introduced 1 ml catalase to 10 ml H2O2. The experimental groups (EG) introduce 1ml catalase to a series of manipulated pH of H2O2 solutions.: EG #1 – 1 ml pH 9 added to 10 ml H2O2, EG #2 – 1 drop of NaOH added to 10 ml H2O2, EG #3 – 3 drops NaOH added to 10 ml H2O2, EG #4 – 2 drops HCl added to 10 ml H2O2, EG#5 – 1ml pH 2 added to 10ml H2O2, and EG #6 – 10 drops of NaOH added to 10ml of H2O2.. The pH of the substrate and enzyme were acquired and the resulting Experimental Group pH recorded and listed in the table below:

Experimental Group pH added to 10ml of H2O2 Resulting pH

EG #1 1 ml pH 9 pH 8

EG #2 1 drop NaOH pH 10

EG #3 3 drops NaOH pH 11

EG #4 2 drops HCl pH 2

EG #5 1 ml pH 2 pH 4

EG #6 10 drops of NaOH pH 13

Control Group - Substrate -------------------------- pH 6

Control Group - Catalase ---------------------------- pH 6

The lab apparatus