In this investigation I will investigate the effect of the enzyme Catalase on Hydrogen Peroxide by measuring the volume of oxygen gas produced in a certain time. All living cells contain Catalase in them and so instead of using a Catalase solution I will use a yeast solution. The reaction of this experiment will be as follows: Hydrogen Peroxide Water + Oxygen Hypothesis My hypothesis for this experiment is that I think as I increase the concentration of Catalase, the rate of oxygen produced will increase as long as there is always excess substrate (H2O2).

I am going to now explain what an enzyme is and this will help me to justify my hypothesis. An enzyme is a protein which acts like a biological catalyst, and the definition of a catalyst is a substance that speeds up a reaction, but is not chemically changed at the end of the reaction and therefore is never used up in a reaction. From preliminary work I have done on enzymes I know this to be true because I have done an experiment in which I measured the mass of Manganese (IV) oxide (MnO2) (also a catalyst of H2O2) before adding it to Hydrogen Peroxide.

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Then after the reaction had finished I measured the mass again. And as I suspected the mass remained exactly the same and so this proves the fact that the catalyst is unchanged. Every enzyme has an active site. Active sites are where the reactions happen. The reactions occur when a substrate molecule (hydrogen peroxide) fits into one of the specialised active sites of a Catalase enzyme. This is called the lock and key method. I will know explain this in more depth. Every enzyme is specialised to only one type of reaction because of the shape of its active site.

Enzymes can only fit one type of molecule into their active sites; this is shown by the diagram below The diagram above shows one type of enzyme and two types of substrate and that only one of the substrates fit into the enzyme. This fit means there would be a successful reaction. Enzymes can have two different types of reactions, a breaking down reaction, Catabolic and a building up reaction, Anabolic. The reaction that I will be doing is a catabolic reaction and it will go as follows:

Catalase also has a special feature in its make up; it has four active sites instead of one so this means that more than one reaction can happen at the same time on the same molecule of Catalase. I will now try to prove my hypothesis in two ways, both of Collision Theory. Collision theory is a theory that states particles are always moving and colliding with each other and that reactions happen when molecules collide with each other. But every single reaction needs a certain amount of energy when collisions happen in order to react.

This energy is called the activation energy. A catalyst speeds up a reaction by providing another route for the reaction which requires less activation energy. The following diagrams help me to show this by using the Maxwell-Boltzmann Distribution (this shows the number of particles with a certain amount of energy): The first diagram shows that only a certain amount of particles have enough energy to react, but when the catalyst is added, the new route allows more particles to react because of the fact that the activation energy is lower.

This therefore shows that if there is no catalyst present in the reaction (zero concentration of yeast (control of my experiment)) the rate of oxygen produced will be lower than if there was a catalyst present. In my investigation I will be changing the concentration of yeast (Catalase) in the reaction and my hypothesis states clearly that as concentration of yeast increases so must the rate of oxygen produced. I am now going to try and prove this again by Collision Theory, but this time not of catalysts but of concentration.

In Collision Theory it is well known that if you increase the concentration of particles in a certain area, the number of collision will increase. This can be shown by two very simple diagrams: These two diagrams show that if the concentration is increased the number of collisions will increase, in the low concentration diagram there are two collisions and in the high concentration diagram there are four collisions. Since there are more collisions there will probably be more successful reaction and therefore a higher rate of reaction which will mean a faster rate of oxygen produced.