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Factors That Affect the Rate of an Enzyme Reaction.

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FACTORS THAT AFFECT THE RATE OF AN ENZYME REACTION AIM The aim of this experiment is to investigate one factor that affects that rate of an enzyme reaction. I have decided to examine how the concentration of the substrate hydrogen peroxide affects the rate of reaction of the enzyme catalase, which is produced by yeast. BACKGROUND THEORY Catalysts lower the activation energy for reactions, and the lower the activation energy for a reaction, the faster the rate. Enzymes are biological catalysts; therefore they speed up metabolic reactions by lowering the activation energy of the metabolic reaction. Enzymes do not undergoing any permanent chemical change during the reaction they catalyse, therefore an enzyme molecule can be used over and over again. As a result a small amount of enzyme can catalyse the conversion of a lot of substrate into a lot of product. Enzymes are substrate specific, this means that a different enzyme is needed for each kind of substrate. For example, starch is digested to the sugar maltose by an enzyme called amylase, whereas protein is digested to amino acids by the enzyme protease. Enzymes are made from globular protein i.e. a polymer of amino acids and have a precise three-dimensional structure which includes an active site i.e. pocket or cleft on the enzyme surface. The active site is exactly the right size and shape, and has the correct charge for a molecule of the enzymes substrate to fit into. Therefore the active site determines the specificity of the enzyme. An enzymes active site has two components: a catalytic site and a binding site. The catalytic site is where the chemical reaction catalysed by the enzyme occurs, whereas the binding site is the area that holds or binds the substrate in the correct place on the enzymes surface. An enzymes active site is held together or in shape by: 1. Ionic bonding - part of the enzyme will have a positive charge (+), while the other half will have a negative charge (-) ...read more.


Analysis Of Pilot From the graphs I plotted from the results (time taken for 30cm3 of oxygen to be collected) and further calculations (rate of reaction) I can see that my prediction is correct. This is because as the substrate concentration increases the time taken to collect 30cm3 of oxygen gas decreases and the rate of reaction increases. This is because for 2% the time taken to collect 30cm3 of oxygen is 160 seconds, and the rate of reaction in 0.2cm3/second. Then when the concentration increases by 2% to 4% the time taken to collect 30cm3 oxygen decreases to 77seconds and the rate for reaction increase to 0.4cm3/second. When the concentration further increases to 6% the time taken to collect 30cm3 of gas further decrease to 50 seconds and the rate of reaction further increases to 0.6cm3/second. As the substrate concentration increases to 2% and 10% the time to collect 30cm3 of oxygen yet again decreases to 45 and 38 seconds, and the rate of reaction yet again increases to 0.7 cm3/second and 0.8cm3/second. In conclusion my pilot gives my accurate, valid and theoretically correct results that support and prove my prediction is correct. This also means that the method for my investigation after the two modifications is correct. MAIN INVESTIGATION Apparatus List - Unlimited supply of 10% hydrogen peroxide solution - to act as the substrate - Unlimited supply of distilled water - used to dilute the 10% hydrogen peroxide - Unlimited supply of yeast solution - this is a fungi which produces the enzyme catalyse - Plastic ice cream tub or trough filled with water - Burette (measuring to 50cm3) -used to hold water and measure the volume of oxygen collected. A burette was used because it is extremely accurate to 0.05cm3 and can hold up to 50cm3 of liquid. - Boiling tube - used to hold the yeast/catalase and hydrogen peroxide, it is where the reaction takes place - Bung with delivery tube and syringe needle - 1ml/cm3 syringe (accurate to 0.2ml) ...read more.


Diagram Method 1. Fill an ice-cream tub half full with tap water and place it on a heat resistant mat also as to protect the work surface from spillages. 2. Take a gas syringe and empty it of air, then place the delivery tube attached to the bung of a boiling tube into the opening of the gas syringe. This is done so that the oxygen i.e. gas produced during the experiment will be able to escape into the gas syringe. 3. Place the boiling tube into a water bath whose water temperature is at room temperature i.e. 37?C. 9. Using a burette filled with hydrogen peroxide measure 5ml of hydrogen peroxide. Then using a second burette filled with water measuring 20ml of water. When measuring the volumes of hydrogen peroxide and water the measurement should be taken by looking at at eye level to the middle of the bottom layer of meniscus. This is done to reduce measuring errors and ensure a fair test. 10. After removing the bung with delivery type and syringe needle pour created dilution into boiling tube. T 11. Using a class rod stir the yeast solution to obtain a uniform solution, and then using a 1cm3 syringe measure 0.5cm3 of yeast solution, making sure there are no air bubbles in the syringe. This and measuring accurately is very important to accurately measure the amounts of yeast to ensure a fair test. 12. Now via the syringe needle squirt the 2cm3 of yeast solution into the boiling tube containing the hydrogen peroxide, and immediately start the stopwatch. 13. Bubbles should start to rise up the tube and the gas syringe will move outwards, as soon as the gas syringe passes the 30cm3 mark stop the stopwatch and record the time to the nearest 1/10th of a second. 14. Repeat the experiment with hydrogen peroxide i.e. substrate concentrations of 4%, 6%, 8%, 10% and 0%. The 0% concentration of hydrogen peroxide solution is control to show that at 0% concentration no reaction occurs. Natalia Prochnicka 11R ...read more.

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