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Hydrogen peroxide (H2O2) an Enzymes Investigation

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Introduction Hydrogen peroxide (H2O2) is a toxic, oxidation agent produced during chemical reactions in the body of most living organisms. Examples of reactions are the oxidation of fatty acids and respiration in plants. To combat this, the body also makes the intoxicating enzyme, catalase, which quickly breaks down this chemical into the undisruptive, constructive, and disposable oxygen and water. The enzyme uses hydrogen peroxide as both an electron benefactor and electron receiver. The active site contains an essential haem group (red compound containing iron and forming non-protein part of haemoglobin), which is what attracts the oxygen, which acts as the electron acceptor as part of the hydrogen peroxide, which is capable of reacting as acid and base. Effect of enzyme and substrate temperature on the rate of reaction, a convenient system is provided by the breakdown of hydrogen peroxide into water and oxygen. 2H2O2 ? 2H2O + O2 Found in potato, liver or yeast. Its speed and rate make it a perfect enzyme to conduct an investigation with. The importance of Enzymes: * Used in the food industry to convert starch into glucose and glucose into fructose which is sweeter to release fruit juices from plant cells clarify wine accelerate cheese ripening * Used in medicine to dissolve blood clots and bruises in biosensors to detect diabetics * Used in cleaning washing powders to remove hairs from leather * Used in genetic engineering to cut out lengths of DNA to rejoin pieces to synthesise lots of copies Enzymes are proteins which act as catalysts for biological processes. As catalysts, they increase the rate of reactions without themselves being altered. These molecules are spherical and coil into orb shapes. They coil, so as to have their non-polar, hydrophobic, water hating side chains point towards the centre of the molecule, away from water. This means that they are soluble. The importance of enzymes: Most enzymes work within the temperature range of 5-55 degrees oC they work at a near neutral pH and at atmospheric pressure. ...read more.


will not be able to be recorded as the Bunsen only holds 50cm3 of gas and will make more gas that it can hold. But I if don't use enough I will not get results I can make good results from. The mass of liver must remain constant through all the experiments. I can only use the weight of the liver as a measurement because unfortunately the surface area cannot be calculated, as liver is not solid and cannot be cut into a certain shape. If I use too much hydrogen peroxide would be a waste and if I use too little all the enzymes will not be used. Test experiments: In these small investigations, I am not looking for absolute accuracy, I shall be investigating simple measurements but they are that are critical to the real practical. The experiments I will perform will be according to the same procedure as I have planned for the real experiment and diagrams below but at room temperature around 30� C. it is no where near the point denaturing and not close to halting the enzyme. Safety Hydrogen Peroxide is an oxidising agent and type of bleach, eye protection such as goggles and gloves to protect the hands must be worn, the concentrations I am using are not extremely harmful but precaution must still be taken. If the hydrogen peroxide made contact with the eyes, skin, or clothes, the contaminated clothing must be removed, the skin or eye flooded with distilled water, a medical kit is needed to be at hand in the lab. Medical advice would be necessary if there was any pain caused or any marking of the skin. The H2O2 when reacting has a tendency to froth, care should be taken with regard to the amount of hydrogen peroxide used not to spill or expand over the volume of the test tube or beaker. ...read more.


The enzyme showed signs of denaturing at 57�C, but did not denature fully until around 80�C. The outer cells containing catalase may of reached the denaturing temperature but not the coated ones. How much enzyme is in 1 gram of liver is questionable. The same weight of live doesn't truly determine the same amount of enzyme contained in the liver. So it a piece of liver was collected from the centre of the liver it may contain more or less enzyme than the edge or vice verse or maybe the liver contains the same amount all over. The liver was kept over a series of days and this would of affected the amount of water in the liver. If the water evaporated the catalase would be in a dehydrated form then there could be more in a dehydrated form meaning there for the weight would remain the same but the amount of catalase could be increased. To over come this problem you could dehydrate all of the liver or keep it all moist. I found/collected information on how the errors could be calculated to a percentage this is what I found: To calculate the maximum percentage error, take the minimum value measured by this piece of apparatus. 1. Burette has an error of � 0.04ml. Minimum quantity used for was 5ml. �0.04/5 = �0.8% 2. Thermometer has an error of � 0.5�C. Minimum quantity used for was 15�C. �0.5/15 = �31/3% 3. Measure has an error of � 0.01g. Minimum quantity it was used for was 5.22g. �0.01/5.22 = �0.19% 4. Time measurements were taken to the nearest second. Minimum amount of time was 110 seconds. �0.5/110 = � 0.455% 5. measuring cylinder had measurements correct to �0.05ml. All cylinders volumes were 10ml. �0.05/5 = �1% Total: � 1 � 0.455 � 0.19 � 31/3 � 0.8 = �5.78% Thus the shortest amount of time (110 seconds) could be 104 - 116 seconds. Philip Bradley Page 1 Biology Coursework ...read more.

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