254 ❯ STEP 4. Review the Knowledge You Need to Score High
produced is measured using the color indicator guaiacol. Guaiacol readily grabs and binds
to oxygen, forming tetraguaiacol, a brown chemical. The greater the amount of oxygen pro-
duced, the darker brown your solution becomes. The relative amount of oxygen is deter-
mined by comparing the color of the tube to a turnip peroxidase color chart (a previously
made series of dilutions of the oxygen-guaiacol reaction). Once you’re comfortable with the
experimental setup, you will investigate at what pH peroxidase works its best.Results
You’ll have six test tubes, each with a different pH buffer. Once the reaction has proceeded
long enough to produce a nice color spectrum among all the different pH solutions, record
the color for each tube. Once you use your lab manual’s turnip peroxidase color chart to
help you quantify the relative amounts of oxygen produced, you can graph your data as
color intensity versus pH. Peroxidase is found in many different forms with optimum pHs
ranging from 4 to 11 depending on the source. Turnip peroxidase, for example, tends to
work best at pH 5.Key Concepts- The reaction rate can be affected by four major factors: pH, temperature, substrate con-
centration, and enzyme concentration. - The rate of reaction can be found by measuring either the appearance of product or the
disappearance of reactant. Either measure can provide insight into the effectiveness of an
enzyme’s presence. - When calculating the rate of reaction, remember that the rate is actually the portion of
the graph with a constant slope. - To determine the ideal pH at which an enzyme functions, run the enzyme reaction at a
series of different pH values and measure the various reaction rates.
KEY IDEA