Find out how Copper Sulphate affects the activity of Catalase.

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Salman Uddin

Enzymes Investigation

Aim: To find out how Copper Sulphate affects the activity of Catalase.

Hypothesis: My hypothesis is that if I add the inhibitor (O.5molar Copper Sulphate) to my enzyme (Catalase) and substrate (Hydrogen Peroxide) reaction, the rate of reaction will decrease.  

Equipment List:

O.5 molar solution of Copper Sulphate

Hydrogen Peroxide (20 vol)

Distilled water

2cm3 of 2.5% yeast solution (which in our case is Catalase)

100cm3 measuring cylinder

Water Trough

Stopwatch

8 Test tubes

Side armed test tube

2cm3 syringe with needle

Rubber delivery tube

Glass Delivery Tube

Half cut bung

Clamp

This is a diagram of all the equipment listed above.

I have chosen this set up of apparatus from a choice of three.  I have chosen this apparatus due to faults that could affect the result in the other apparatus.  Out of the other two used a manometer.  So I immediately eliminated that from the choices available.  This is because the dye will be pushed out of the tube, which will make it difficult to record large amounts of oxygen released.  The other choice was using the gas syringe.  At first I thought the gas syringe would be the most suitable apparatus for this experiment however it had its faults.  The tube didn’t move very smoothly and this wouldn’t give very accurate measurements.  So I chose the apparatus in the diagram, on the previous page.  This apparatus was well suited to experiment as hardly any oxygen had a chance of escaping

Variables controlled:

  • The amount of enzyme will be kept the same as it will always be kept at 2cm3
  • The concentration of enzyme will be kept as accurate as possible as well use the enzyme from the same beaker all throughout the experiment
  • Temperature will be kept at room temperature
  • The amount of substrate will always be 20ml

Variables Changed:

  • The concentration of the substrate will be changed. We will change the concentrations of Hydrogen Peroxide by diluting it with distilled water.

Scientific Knowledge:

Enzymes are biological catalysts, which increase the rate of reactions, without being used up themselves.  The enzyme in our experiment is catalase, which is produce by the yeast.  In our reaction the catalase enzyme breaks up the hydrogen peroxide molecules, which is the substrate.  The product from this reaction is water and oxygen.  We measure the amount of oxygen produced so that we can work out the rate of reaction.

The theory that states how enzymes work is called the lock and key theory.  The enzymes have an active site, which connects to a substrate like a key does to a lock.

It then breaks the substrate down into other products.  The substrate and the enzyme must be of the same shape otherwise the enzyme won’t be able to break the substrate.  This is because if they are of different shapes the enzyme and substrate won’t be able to connect.  Different enzymes only work for certain substrates because of their selective shapes.  In our experiment the active site of the Catalase enzyme connects to the Hydrogen Peroxide molecule as they are of the same shape.  Then the Catalase enzyme breaks down the Hydrogen Peroxide molecules into water and oxygen molecules.

Molecules called inhibitors can slow down enzyme activity or even stop them completely.  An inhibitor does this combining with the enzyme itself, hence preventing the substrate from joining it.  In our experiment we will add Copper Sulphate, which I know is an inhibitor. That is the reason that in my hypothesis I predicted that if I added Copper Sulphate the rate of reaction would decrease.  However, there are two types of inhibitors, Competitive reversible inhibitors and Non-competitive irreversible inhibitors.

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Reversible are temporary and when removed the enzyme will resume full activity.

I don’t know what type of inhibitor Copper Sulphate is. Competitive reversible inhibitors are similar in structure to the substrate. It will compete with the substrate for the active site of the enzyme. However, if the concentration of substrate is increased it will reverse the effects of the inhibitor.  This is because there will be too many substrate molecules for the inhibitor to compete with and they will gain access to the active ...

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