In this experiment I am going to try and find out the factors that affect enzyme controlled reactions by using the Catalase in potato.

The factor I am going to investigate is an investigation into the effects of pH on the breakdown of H2O2 by catalase. To make the investigation fair I’m going to control my variables. To control pH I will use a buffer which will always be 5cm3, the substrate concentration will stay the same every time, this means the volume of H2O2 (hydrogen peroxide) will always be 5cm3 each time, the tests will all be done at room temperature, the tests will be repeated to get an average and my weight of potato will be the same for each of the experiments.

Potato is good substance because it contains many active sites to react with. I will be changing the pH in order to measure the effects on the rate of catalase activity. In this experiment the five pH’s I will be using are: pH2, pH4, pH6, pH8 and pH 10. 

At low pH’s the enzymes are denatured because the pH interferes with the bonding of the amino acids and the shape of the active site is changed. As you increase the pH, the enzymes and substrates gain more energy. They move around more and collide more frequently, so the substrate (key) hits the active sites (lock) of the enzyme more often. This means more collisions increase the rate of reaction, which is called the ‘collision theory’. Eventually as you increase the pH, the optimum pH (the ph that causes the greatest rate of reaction) is reached, so the pH is not interfering with the bonding of the amino acids. After the optimum pH is reached denaturing starts to occur. Above that pH the enzyme starts to denature (change in shape). The enzyme changes shape because heat causes to many vibrations inside the enzyme Therefore the active site changes shape; the substrate no longer fits into the active site, so the rate of reaction decreases and is slow.

To increase the accuracy of my investigation I will create a detailed plan, have several diagrams and note down a risk assessment. The potato size will have to be small enough to be completely submerged in hydrogen peroxide (the substrate). . After doing my preliminary test I discovered that if the potato was measured in length then this could be inaccurate e.g. dents. Doing a preliminary test before means I will know how to set up equipment and do the experiment, this will mean I make fewer mistakes. There are several factors which are difficult to control