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Investigating enzyme catalysed reactions.

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Biology Coursework Investigating enzyme catalysed reactions Introduction For my biology coursework I will be investigating enzyme catalysed reactions and their effects. In this project I hope to extend my knowledge of enzymes and catalysts and research my own experiment that will further and confirm my findings. I will examine how the concentration of the substrate hydrogen peroxide (H202) affects the rate of the reaction of the enzyme catalyses. Background information Enzymes Enzymes are protein molecules produced by living cells. Each cell contains several hundred enzymes. Enzymes can be defined as biological catalysts because they speed up reactions. Enzyme reactions may be either anabolic (involved in synthesis) or catabolic (involved in breakdown). The sum total of all these reactions in a living cell or organism constitutes its metabolism. Therefore metabolism consists of anabolism and catabolism. Enzymes serve to control the chemical reactions that occur within cells and ensure that they proceed at an efficient rate. Biological catalysts possess the following major properties: * All are globular proteins * They increase the rate of reaction without being used up * Their presence does not alter the properties of the end product * A small amount of catalyst effects the change of a large amount of substrate * Their activity varies with Ph, temperature, pressure and substrate/enzyme concentrations * The catalysed reaction is reversible * Enzymes generally catalyse only a single reaction The energy required to make substrates react is called Activation Energy ( ) The greater the amount of activation energy required, the slower will be the rate of reaction at a given temperature. Enzymes, by functioning as catalysts serve to reduce the activati0on energy required for a chemical reaction to take place. They speed up the overall rate without altering, to any great extent, the temperature at which it occurs. An enzyme combines with its substrate to form a short-lived enzyme/substrate complex. The chances of a reaction are greatly improved within this complex. ...read more.


For my experiment I need primarily to find out the maximum rate of reaction for my particular investigation which, is to use potato and hydrogen peroxide. To enable me to do this I will set up a preliminary experiment to find the maximum rate For my investigation VARAIBLE * Concentration of the substrate (H202) KEEP THE SAME * The enzyme catalyse(potato) * Mass of potato * Amount of water in the box and measuring cylinder * Same equipment * Same temperature Prediction I predict that the hydrogen peroxide will break down to the products of oxygen and water in the presence of catalyse. I think that an increase in substrate concentration will speed up the reaction. This will occur up until the substrate as taken up all the remaining active sites. It is then that the reaction will stop increasing. Equipment List * hydrogen peroxide * test tube rack * plastic container * a potato * a cork borer * water * measuring cylinder * clamp/clamp stand * stopwatch * 2x 10 mml syringe * scales * a ruler * 5 boiling tubes * bung/rubber tubing * tile * scalpel * 3x beakers * safety goggles Method To investigate my task I set up the following experimentation: * Fill up a plastic container to half its volume with water (make sure that this volume of water remains constant throughout the investigation). Fill a measuring cylinder to the brim with water. Turn the cylinder upside down so that it stands upright inside the plastic container. Use the clamp and clamp stand to support the free standing measuring cylinder. * Set up the boiling tube inside the test tube rack, with the bung and rubber tubing connected to the mouth of the boiling tube. Whilst one end of the rubber tubing is attached to the boiling tube, the other end should be joined to the inside of the measuring cylinder, within the plastic container. ...read more.


Variables - In this investigation, the variables that affect the activity of the enzyme, Catalase, were considered and controlled so that they would not disrupt the success of the experiment. i) Temperature -To control this variable, the temperature was maintained at a fairly constant level that allowed the enzyme to work effectively (room temperature, approximately 23�C). This was achieved by using a test tube rack and tongs to handle the apparatus so that the heat from my hands did not affect the Catalase. ii) pH -In this experiment, the pH was kept constant using a pH 7 buffer, selected to maintain a pH level suited to the enzyme by being equal to the natural environment of the enzyme (potato tissue). iii) Substrate Concentration To control the substrate concentration, identical quantities of the substrate were used for each reading. To ensure that this was measured precisely, 5ml syringes were used to accurately gauge to exact quantities. iv) Inhibition - Inhibitors compete with the substrate for the active sites of the enzyme (competitive inhibitors) or attach themselves to the enzyme, altering the shape of the active site so that the substrate is unable to occupy it and the enzyme cannot function (non-competitive inhibitors). Inhibitors therefore slow the rate of reaction. They should not have affected this investigation, however, as none were added) Enzyme cofactors - cofactors are none protein substances which influence the functioning of enzymes. They include activators that are essential for the activation of some enzymes. Coenzymes also influence the functioning of enzymes although are not bonded to the enzyme. Unless enzyme cofactors were present in the potato tissue containing the Catalyse, they were not included in this investigation and therefore would not have affected the rate of reaction and the results of this experiment. vi) Enzyme Concentration -I varied the enzyme concentration by altering the number of equal sized discs of potato that contain the Catalyse, in the reaction. The greater the number of discs, the greater the enzyme concentration. ...read more.

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