What affect the substrate has on the rate of reaction with the enzyme in potato?

Essay by jimbarson February 2004

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Enzyme Investigation


To find out what affect the substrate has on the rate of reaction with the enzyme in potato.


1. PH

2. Temperature

3. Concentration of substrate

4. Concentration of enzyme

5. Surface area of potato lumps

6. Time

Key Variables

Input variables - concentration of substrate

Output variable - volume of gas


I think that to start with, the higher the concentration of the substrate the faster the rate of reaction. However, I think that eventually the graph will start to level off because the enzymes will reach the highest level at which they can work.

I will keep the other variables constant to make the results more accurate and fair.


1. Put a set amount of potato into the conical flask.

2. Then add the chosen concentration of hydrogen peroxide.

3. The bubbles go through the rubber delivery tube and push water out of the measuring cylinder (the measuring cylinder is sat in a tub of water).

4. We stop after a set time and measure the volume of gas.

5. Repeat this process with the next concentration of the substrate (hydrogen peroxide.)


I will wear safety goggles throughout and handle the hydrogen peroxide with care.


After my preliminary tests I found that my original ideas for measurements made the reaction too fast. So now I am going to use 30 cm3 of hydrogen peroxide and 5g of potato each time. This gives a steady reaction that can be easily monitored and measured. I will be using the same amount of hydrogen peroxide each time but adding water to it, this will change the concentration.


Because of my reaction speed with the stop watch I approximate the a few bubbles of gas may pass before I take a reading,