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Enzymes - show how substrate concentration affects the rate of reaction for an enzyme controlled reaction.

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Biology Coursework: Enzymes Aim: My aim is to show how substrate concentration affects the rate of reaction for an enzyme controlled reaction. Equation: Catalase Hydrogen Peroxide (2H O ) Water (2H O ) + Oxygen (O ) Introduction: Enzyme is a protein produced by a living organism that acts as a catalyst in a specific reaction by reducing the activation energy. A globular protein, enzymes have a specific three dimensional shape which is determined by the sequence of amino acids. The region which makes the enzyme specific and functional is known to be the active site. As result of this only the substrate which is complementary to the enzyme active site will be able to fit and form an enzyme-substrate complex. ACTIVE SITE SUBSTRATE ENZYME Enzyme + Substrate SUBSTRATE FITS INTO ACTIVE SITE OF ENZYME ENZYME Enzyme-Substrate Complex Lock and Key Theory: This theory outlines the fact that an enzyme is specific for a substrate. This is shown by using an example of lock and key. This states that as a key is specific in shape it fits into only one lock in order to function. Hence the substrate will only fit into one active site provided by a specific enzyme. As result the shape of the substrate (key) exactly fits the active site of a specific enzyme (lock). Induced Fit Theory: This theory suggests that the enzyme doesn't have to be specific for a complementary substrate as it is stated in the lock and key theory. This theory states that the enzyme is flexible hence has the ability to change its shape in order to allow it to fit the shape of the substrate. Also as the enzyme alters the shape, the enzyme puts on the substrate molecule as result of this it lowers the activation energy. Activation Energy: Activation energy is the energy that must be provided to make a reaction take place, enzymes reduce the activation energy required for a substrate to change into a product. ...read more.


Syringe - 10 cm� 2 Use to transfer hydrogen peroxide into the boiling tube. This is because the 20 cm� syringe will have a smaller scale hence a larger percentage error. Therefore I will use a 10 cm� syringe because the percentage error caused will be lower. Burette - 50 cm3 1 Measure the volume of oxygen produced. Clamp and stand 1 Hold burette in straight in large beaker so the reading taken is accurate and reliable. 2.0 M Hydrogen peroxide solution 50 cm� Use to dilute to produce the required concentrations. Also is the substrate that is catalysed. Plasticine - Use to make top of bungs airtight so oxygen can't escape. Rubber bungs 12 Use to cap dilutions of hydrogen peroxide solution until use. Potato 120-130 1mm thick discs Contains catalase hence used to catalyse hydrogen peroxide. Cork borer 1 To gain the same diameter of potato, this is smaller in diameter of the boiling tube diameter. Knife (scalpel) 1 It is required in order to cut the potato, 1mm thick. pH7 buffer solution 20 cm� Used to keep the potato moist Method: * Firstly get all the equipment required. * Wear goggles and follow other safety precautions. * First of all, using a cork borer (a little smaller in diameter than the boiling tube), cut a cylinder of potato. * Use the knife (scalpel) to cut the potato cylinder into 1mm thick discs. * Place 3 cm� of pH7 buffer solution in a watch glass. * Place the potato discs in the watch glass, which contains ph7 solution. This will keep the potato discs moist. * Place ten potato discs in a boiling tube with 3 cm� of pH7 solution and cover it with a bung with a gas deliver tube. * Place the boiling tube containing potato discs and pH7 solution in the thermostatically controlled water bath, at the temperature of 35�C. ...read more.


Fair Test: There are certain variables, which I would need to keep the same in order to carry out the experiment because the change of those particular variables may lead to unfair results. Those variables, which are required to be controlled throughout the experiment, are the volume of catalase and hydrogen peroxide used. I will only use 10 cm� of catalase and 20 cm� of hydrogen peroxide throughout the experiment in order to obtain reliable results and also allow the same volume of reactants to react with the at different concentrations of hydrogen peroxide. This is important because the more catalyse used the faster the rate of reaction hence the concentration of the catalase and the volume of catalase used for each concentration is to remain the same. Blank Results Table: A blank result table to show the volume of oxygen collected (cm�) when different concentrations of hydrogen peroxide are catalysed by catalase. Percentage concentration of Hydrogen Peroxide (%) 10 (0.2M) 40 (0.8M) 50 (1.0M) 60 (1.2M) 80 (1.6M) 100 (2.0M) Time (sec) 1st time 2nd time Ave. 1st time 2nd time Ave. 1st time 2nd time Ave. 1st time 2nd time Ave. 1st time 2nd time Ave. 1st time 2nd time Ave. 0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 30 1.20 1.10 1.10 1.90 2.15 2.40 2.45 2.55 2.50 3.50 3.90 3.70 4.90 5.20 5.05 6.20 6.50 6.35 60 1.90 2.00 2.00 3.60 3.93 4.25 4.95 5.00 4.97 6.70 7.10 6.90 9.20 9.60 9.40 11.6 12.2 11.9 90 2.50 2.90 2.70 4.35 4.93 5.50 6.95 7.10 6.97 9.30 9.50 9.40 12.8 13.6 13.2 16.4 17.6 17.0 120 3.10 3.50 3.30 5.50 5.85 6.20 8.60 8.70 8.65 11.6 11.8 11.7 16.1 17.7 16.9 20.7 23.5 22.1 150 3.90 4.10 4.00 6.20 6.40 6.80 10.3 10.5 10.4 14.1 14.3 14.2 18.8 21.6 20.2 24.8 27.6 26.2 180 4.30 4.90 4.60 6.80 6.90 7.00 11.6 11.8 11.7 16.7 16.9 16.8 23.0 25.2 24.1 29.2 32.8 31.0 Biology Coursework: Enzymes Yahyah Aman 12T ...read more.

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