As the enzymes are proteins they will break down at high temperatures as the molecules start to vibrate and then lose their shape. The enzyme then loses its three-dimensional shape and the substrate no longer fits into the active site. The enzyme is now denatured. As of this high temperatures reduce enzyme activity. Every enzyme has an Optimum Temperature which is a balance between the two effects of temperature. Denaturisation is usually irreversible, and living cells make great efforts to keep the conditions suitable for the enzymes to work. I.e. The body temperature is at 37 degrees centigrade which body enzymes work at best. This is their optimum temperature.
Enzyme is denatured and the substrate molecule no longer fits the active site.
Catalase is an enzyme and is the fastest enzyme known. It catalyses (speeds up) the Breakdown of Hydrogen Peroxide. It is found in many living cells.
Catalase
Hydrogen Peroxide → Water + Oxygen
Hydrogen Peroxide is often formed as a product of reactions in cells. It can be poisonous if it builds up, so Catalase has to work quickly so it does not build up to much poisoning the cells and killing them.
Prediction: Based on the research above I think the enzymes will work best at 37 degrees C as this is body temperature. I think this is the enzymes Optimum temperature and will be able to react best with the substrate molecules as they would be moving about more and colliding more with the enzyme molecule increasing the chance of them reacting. This is called a successful collision. At optimum temperature the Enzymes react quicker. In this experiment it will be a catabolic reaction as the catalase enzymes will be breaking down the Hydrogen Peroxide molecules into water and oxygen molecules.
Catalase Enzyme
Hydrogen Peroxide
Molecule
Water Molecule
Oxygen Molecule
Equipment :
Boiling tube Thermometer
Gas syringe Beaker
Bunsen burner Heat Proof Mat
Gauze Hydrogen Peroxide
Tripod Water
Ice Liver (catalase)
Test tube Chronicle flask
Rubber but -
and tubing Scalpel
Ruler Stop watch
Pipette Measuring cylinder
Temperatures: The temperatures chosen to heat the sodium peroxide are as follows - 0 degrees C, 10 degrees C,20 degrees C, 30 degrees C, 40 degrees C, 50 degrees C 60 degrees C and 70 degrees C. This is because I believe that the enzyme will work best at Body Temperature which is roughly 35 degrees C, I think this is its optimum temperature at midway point the balance between the two effects of heating.
Method: After collecting all the equipment and placing them in place it is advised that you first see what temperature the Hydrogen Peroxide is at, it will most probably be at room temperature which is about 18 degrees C so it is advised to heat it up to 20 degrees as it is the quickest, what also would be advised at this point is to put Equal amounts of Hydrogen Peroxide (we used 5 ml3) into a three test tubes and place these into a beaker of ice and start the long process of cooling the Hydrogen Peroxide down to 0 degrees C(this will save time). To heat it up use the same process as before but instead put the three equal amounts of Hydrogen Peroxide into test tubes and then into a Beaker of water. Place the Beaker onto a tripod and gauze and proceed to heat it with a Bunsen burner which is placed on the heat proof mat. When heated to the desired temperature you should immediately add this to the little disk of liver (This helps keep it a fair test as no heat is lost), which has been placed in the chronicle flask. Each disk of liver has to be the same size (we used 5mm thick diskd). So, you can cut this with the ruler and scalpel to the length needed. When the Hydrogen peroxide is added to the liver the But and plastic tubing which is connected to the gas syringe must be connected immediately. When this is all connected just as in the diagram, you should record at what point the gas syringe is at with time intervals e.g. every 10 seconds. It would be more accurate if you done the experiment three times at each temperature so an average can be made.
Fair Test: we will try to make sure it is a fair test by keeping all measurements equal each time in every experiment. I.e. we will keep the hydrogen peroxide at 5 ml3 each time this will make sure that the concentration of the solution does not affect our results, this will be done by accurately measuring it out with a pipette and measuring cylinder. Also the liver will be cut to 5mm thick each time making sure that there are no more enzymes in one experiment than the other. Each experiment will be done three times so an average can be taken.
Safety: As Hydrogen Peroxide is an irritant solution goggles will have to be worn at all times. Long hair will have to be tied back as of open flames and as glass is being used their should be no silly behaviour and no bags in the corridor for people to trip over.
Observations>
Results:
Average Results:
There seem to be no anomalous results as the temperature increases steadily with each time interval and the reactions seem to become quicker with each rise in temperature.
Analysis>
My experiment has shown that with the increase in temperature the more oxygen and water has been produced by the reactions and at each temperature the oxygen and water produce rises steadily.
This shows that when the enzyme is heated the substrate molecules do move around more increasing the chance of a reaction between the enzyme and the substrate molecule.
As the substrate molecules are heated they move around more and at a faster rate the chances of a reaction greatly increase. As they are moving round quicker they react quicker so the enzyme reacts with many substrate molecules at a faster rate.
As the enzyme did not get heated it self and stayed at a constant temperature it did not denature. If the Enzyme was heated past its Optimum Temperature it would denature and the rate of reaction would greatly decrease as the substrate would no longer fit in the active site.
An enzyme-catalysed reaction gets quicker as it reaches its optimum temperature, but after it passes because of heating it further it will slow down as the enzyme has become denatured.
This information shows why my predictions were wrong, I referred to the enzyme working best at body temperature and then decreasing after that at a higher temperature as the enzyme denatured. This did not occur because the enzyme was not heated itself and stayed at a constant temperature. Instead we heated the Substrate molecules instead (hydrogen peroxide) and this showed that with increasing temperatures of the substrate molecule the enzymes reacted quicker. This occurred because as the substrate molecules were heated they moved around more increasing the chance of them having a successful collision and reacting.
Evaluation:
The experiment went ell as we worked together in a group to complete the experiments in a fast time with accuracy. Even though there are no anomalous results there were still factors on how to make it an even fairer test The experiment could be performed in a vacuum so none of the gasses given off in the reaction could have escaped, also the liver was not cut very accurately and to make sure you had the same amount each time measuring scales to three decimal places could have been used, making sure each disk was the exact same weight.
My results are accurate and prove that when the substrate molecule is heated it moves around more increasing the chance of a reaction. They are reliable as there seems to be no anomalous results and that we made the experiment as fair as possible.
To find out more about enzymes, catalase you could find an industry that uses enzymes to lower temperature to save money and how they makes sure everything is carried out at a suitable standard. You could also connect to the internet and find out more about our biological catalysts.
