Potato Enzyme Lab

Words: 1890
Pages: 8

A Study on Enzyme Kinetics by Substrate Concentration and pH
Colin Kuehnel

Abstract
An enzyme is capable of increasing rate (speed) of a reaction by lowering the activation energy of said reaction, specifically in our case the enzyme catalase. Like most things in the world, enzymes are subject to their environments and have ideal conditions in which they perform the best. Our experiment tested the performance of catalase under a variety of conditions including fluctuating pH, presence of inhibitors, substrate and enzyme concentrations, and changes in temperature, all of which you will soon learn, do influence the kinematics of enzymes.
Abbreviations
Vmax= maximum velocity
Km= Michaelis-Constant
½ Vmax = Km mls = milliliters
H2O2 = hydrogen
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Prior to examining the kinetics, the enzyme needed to be prepared. This was done by peeling the skin off bagged potatoes. These skin peels were roughly 1/8” to ¼” thick, and consisted of both, the exterior and interior of the potato. Once a sufficient amount of potato skins were peeled, they were placed within a juicer and a beaker labeled “potato juice” was placed under the outlet faucet of the juicer. About 4 mls of 7.2 pH Citrate Buffer was placed in the juicer along with the potato skins. The juicer was then turned on and juice collected in the “potato juice” beaker. This was repeated three more times, adding about 4 mls of buffer to the ever more deteriorating potato skins within the juicer. The raw potato juice was then filtered through cheesecloth, into a new beaker labeled “Catalase Extract.” Upon straining and collecting about 20 mls of catalase extract, the entire juicer was broken down, cleaned, dried, and set back up for the next …show more content…
All trials, Varying pH, altering substrate concentrations, and the presence of an inhibitor all change and alter the reaction rate of enzymatic reactions. As one can see in Table and Figure 1 below, pH does indeed alter the rate of the enzymatic reaction. pH Total ml O2 evolved Rate, (ml O2/sec)
5.8 16.8 0.140
6.6 25.2 0.210
7.2 31.2 0.260
7.8 27.9 0.233
8.8 26.2 0.218
Table 1: summarizes the total evolved O2 and rates (ml O2/sec) of each pH trial using the optimal 75% Catalase Solution.

From this data, we can conclude the most optimal pH is that of 7.2, this pH possessed the quickest rate of 0.260 ml O2/sec and evolved 31.2 ml. This optimum may be due to the potato’s and most other plants ideal pH range of 6.2 – 7.8. (Waterer, 2002)
Varying substrate concentrations as seen in Figure 2 also effects reaction rates, while Table 2 depicts the increase in both concentration and rate, from our data, one can conclude the 1.32M yielding the highest rate of 0.400 ml O2/sec. This I believe is inconclusive due to the similarity between 1.32M yielding 0.400 ml O2/sec and 1.47M yielding a rate of 0.398 ml O2/sec.
Concentration, (M) Total ml O2 evolved Rate, (ml O2/sec)
0.147 19 0.158
0.367 24.1 0.201
0.733 39.8 0.332
1.10 46.4 0.387
1.32 48 0.400
1.47 47.8