The reaction of the enzyme takes place on the active site. The active site brakes down the substrate that fits into it. So enzymes can only break down one type of substrate. The enzymes can work over and over again though once the substrate leaves the active site.
Variable
The variable in this experiment is the concentration of the solution (hydrogen peroxide) reacting with the enzyme. I will keep the all other effecting factors the same. Temperature, weight and surface area of potato, amount of hydrogen peroxide and the ph conditions.
If I change the temperature the enzyme will work differently if the temperature goes over 40º the active face will denature and the enzyme will not work at all.
If I change the surface area there will be a greater area of enzyme to react with the hydrogen peroxide.
Safety
I will were goggles at all times during this experiment because hydrogen peroxide is hazardous. If I get any on my hands I will wash off straight away.
Method
I will full a water bath full of water. I will fill a measuring cylinder full of water and turn it upside down in the water bath making sure no water gets out. I will then make up different concentrations of hydrogen peroxide up. I will do this by mixing the hydrogen peroxide up with water. E.g. 5ml of water 15 ml of hydrogen peroxide. I will do this for concentrations 20, 17.5, 15, 12.5 and 10 molar. I will then cut up small cubes of potato. I will d my best to try and make each cube to have an equal surface area and will weigh them to make sure they are all roughly the same weight. I will drop the potato into the acid and immediately put a bung over it and start the stopwatch. The bung is connected to a pipe, which will run-through, and into the measuring cylinder. I will time how long it takes to collect 5m³ of gas given off. I will do this 3 times and then take an average.
Diagram
Results
Average Time taken to collect 5ml of gas in seconds
Conclusion
After doing this experiment I can conclude that enzymes work faster in higher concentrations of substrate. This is because with more substrate in a solution the faster the enzyme will collide with the substrate and break it down. This means that my prediction was correct. I predicted correctly because scientific knowledge I knew.
