Investigating the Properties of the Enzyme Catalas
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Investigating the Properties of the Enzyme Catalase
The discovery of enzymes occurred accidentally in the late nineteenth century. The German chemist Eduard Buchnar had been attempting to harvest fluid derived from yeast extracts, to his exasperation the fluid extracts taken kept decaying. With the knowledge sugar acts as a preservative of fruit, Buchnar introduced sugar to his liquid extracts in the hope the sugar would preserve the yeast extracts. To his astonishment the yeast fluid dissolved the sugar resulting in fermentation, producing alcohol. Twenty years prior to Buchnarís findings Louis Pasteur had already established fermentation could be achieved by using yeast. Pasteur believed the living yeast cells caused the fermentation to take place. As Buchnarís findings show the fluid from the yeast was in fact responsible.
Enzymes are globular (complex three dimensional) proteins which consist of polypeptide chains joined together. They are responsible for all the biochemical reactions in the body. Divided into two groups, extracellular (produced inside the cell, used outside the cell i.e. digestive enzymes (pepsin) break down food in the gut) and intracellular (used to speed up and control metabolism (ATPase) inside the cell). Enzymes act as catalysts, (substances that speed up the rate of a chemical reaction by reducing the activation energy necessary to initiate the reaction, without changing the enzymeís properties). Enzymes do not make fresh reactions occur; they only balance an ongoing reaction at a safer and lower temperature (at the same rate as the living organisms in the body). Enzymes provide an active site (a three-dimensional structure which only admits a relevant substrate) described as working on a lock and key basis. (This basically means if the substrate is the right shape and correct biological property it can bind with the enzymes active site).
There are a number of factors that can either aid (activator) or hinder (inhibitor) the reaction rate of an enzyme. An activator interacts with the enzyme and increases its activity, whereas an inhibitor binds with the enzyme to decrease its activity.
The experiment to be carried out focuses on the enzyme Catalase. Located in the peroxisome (cell organelle responsible for the oxidation of fatty acids and synthesis of cholesterol and bile acids). The substrate to be used (Hydrogen Peroxide) is a product produced by the oxidation of fatty acid and also produced by phagocytes in white blood cells (to kill bacteria). Catalase has the ability to spilt hydrogen peroxide into water and oxygen. The purpose of the experiment is to investigate the properties of catalase.
Before the experiment can be performed the following safety precautions should be observed:
v Laboratory coat must be worn to avoid spillage of corrosive substances on skin and clothes.
v Eye protection must be worn to avoid substances coming into contact with eyes.
v The location of the eye station (medical eye wash kit) should be noted in case of substances coming into contact with the eyes.
v If H2O2 is spilt onto the skin rinse under water immediately. Inform person regulating the experiment.
v When handling the liver follow basic kitchen rules, (use chopping board, wash hands after contact, all waste liver in the bin).
v To enable safe discard of waste liquid substances, the experiment should be performed next to a sink.
The following equipment is required:
v Cutting board
v Scalpel to cut liver
v Tweezers to handle liver
v 1ml syringe for teepol
v 5ml syringe for H2O (distilled water)
v Syringe for H2O2
v Time piece (stopwatch)
v Measuring cylinder.
v 9 equal portions of liver
v 27ml of H2O2 (20 vols) Hydrogen Peroxide
v 9ml of teepol
v 48mls of H2O (water)
4ML H2O2 (20 VOLS)
EACH TEST NEEDS TO BE REPEATED 3 TIMES TO OBTAIN AN AVERAGE.
Once the safety rules have been observed and all equipment gathered the experiment can commence.
The ingredients need to be added in the correct order shown in the table above, i.e. for test 1 add the teepol first, H2O2 second, liver third and lastly add H2O.
As soon as all the ingredients have been added to the cylinder start the time piece. After 30 seconds has passed measure the amount of foam in the cylinder, repeat this process every 30 seconds until the foam measures the same on three consecutive times. Record answers, and then repeat each test twice to achieve an average.
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Chemistry, Catalysis, Metabolism, Enzymes, Disinfectants, Household chemicals, Enzyme, Catalase, Peroxide, Foam, Hydrogen peroxide, Insulin
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