Investigating a factor that affects the rate if enzyme activity
S(a)
Possible Independent Variables * Concentration of substrate – different concentrations of the substrate can have an effect on the rate of reaction due to more particles in the solution therefore increasing chance of the particles colliding. * pH – different pH levels can have an effect on the rate of reaction due to the interference of bonds that hold the enzyme together in the active site. Therefore the specific substrate will not fit into the active site * Temperature - the temperature can have an effect on the rate of reaction. This is because when a substance is heated the particles will move faster therefore increasing the chance of collisions between the particles. * Concentration of enzyme – different concentrations of the enzyme can have an effect on the rate of reaction due to more particles in the solution therefore increasing the chance of the particles colliding. * Source of catalase – depending on the source of catalase you are using can also have an effect on the rate of reaction. There are many different sources of catalase such as potato, liver and spinach. Depending on which source you are using for your catalase can produce different results.
I have chosen to investigate the effect of changing the concentration of enzyme on the rate of catalase activity. I have chosen this independent variable because it will be easy to monitor and change considering that the experiment is kept as fair as possible. It is also easy to measure with the equipment that is available to us.
Hypothesis
I predict using the information researched that the rate of reaction for the enzyme will be directly proportional to the enzyme concentration. I think the optimum rate of reaction will depend on the enzyme concentration. This is because enzymes can only react with a specific amount of substrate at a given amount of time. Therefore if you were to decrease the amount of enzyme concentration then the reaction would take longer. This is due to the fact that there will not enough particles to react with the substrate. For example if I put in 2g of potato then the reaction will be slower than if I put in 20g, which will then react faster.
Variables
Independent
Concentration of enzyme

Dependent
Volume of oxygen (cm3)
Control
* Volume of hydrogen peroxide (cm3) * Volume of pH buffer solution (cm3) * Temperature of water in the tray * Time (seconds)
It is important that all the control variables of the experiment are kept the same. This is to ensure that all of the results are accurate and reliable, and that any changes to the enzyme are caused by the change of the concentration of enzyme and no other factors. This will help to make the experiment a fair test.
S(b)
Equipment list * Potatoes – This is the source of the catalase enzyme. It is important that each sample is taken from the same potato to avoid any variation in catalase levels due to different potatoes. We will be using diced potatoes. This will make it easier to adjust when measuring for the concentration. It will also break open the cells, which releases more enzyme and will speed up the rate of reaction. * Hydrogen Peroxide – This is the solution we will be using as the substrate for the catalase. The volume of solution we use will be the same each time. * Safety Goggles and Lab Coats – this is to make sure that we protects our eyes and clothes from the hydrogen peroxide and the pH buffers. This is because hydrogen peroxide is a bleaching agent. * Buffer Solutions – These are the pH buffers that we will be using. We will be using the level 7 buffer solutions each time. * Boiling Tubes – The size and depth of the boiling tube will be kept the same so that the volume of solution will not vary each time we do the experiment. * Delivery Tube – The delivery tube will be used to transfer the oxygen in to the measuring cylinder