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Researching enzymes and their properties.

Extracts from this document...

Introduction

HAYLEY PEARCY 10HOo BIOLOGY COURSEWORK. INTRODUCTION (With help from 'Biology, a functional approach second edition' by M.B.V. Roberts.) First I am going to research enzymes and their properties to get a bit of background information. WHAT ARE ENZYMES? An enzyme is a biological catalyst. They were first discovered by the German chemist Eduard Buchner. There are now over 700 different types of enzymes identified. They affect the speed of a lot of the chemical reactions engaged in the metabolism of living organisms. The chemist, 'Jons Jakob Berzelius' suggested that enzymes are typical catalysts. They increase the rate of a reaction without themselves being used up. Enzymes are made up of polymers of amino acids HOW DO THEY WORK? The way in which all enzymes work has been named the lock and key hypothesis. All types of enzymes are individually shaped. Some control many reactions whereas others only control individual reactions. Below is an example of the lock and key method in action. Normally the enzyme will be more complex shape but for this purpose I have drawn a simple diagram. The first picture shows the substrate locking into the active site of the enzyme. The active site is where the reaction takes place and it is made up of amino acids. The substrate binds into the enzyme active site and then reacts to form the product. Picture 2 shows the substrate after the reaction. The products leave the active site and make way for another substrate molecule. The shapes of the enzyme active site and the substrate molecule need to match perfectly otherwise the reaction will not take place. The catalyst can also be reversed to make substrate molecules out of the products PROPERTIES OF ENZYMES. Enzymes are proteins therefore they have the same characteristics as proteins. * They can greatly increase the rate of a reaction compared to an inorganic catalyst, as they are more successful in lowering the activation energy level. ...read more.

Middle

If my prediction is true then my graph should have a positive correlation and its gradient should get gradually smaller. APPARATUS. A. 3x100ml beakers. One for the catalase, one for the hydrogen peroxide and one for the distilled water. B. 3xpippettes. One for the catalase, one for the hydrogen peroxide and one for the distilled water. C. 3x10ml measuring cylinders. One for the catalase, one for the hydrogen peroxide and one for the distilled water. D. Conical flask. E. Bung and delivery tube. F. Washing up bowl 1/2 filled with water. G. 100ml measuring cylinder. H. Goggles. I. Stopwatch. The variable that I will change in my investigation will be the concentration of the substrate. I will try to keep every other possible variable the same for each experiment to reduce the risk of affecting my results. I will measure the amount of oxygen produced in a set amount of time that should give me the changing speed of the reaction. METHOD. * I will start by setting up the apparatus as shown above. I will put my goggles on as instructed by the hazchem code for these substances. * Using the pipettes as they are a more precise way of measuring, I will measure out first 5cm3 of catalase from the beaker to the measuring cylinder and then do the same for my chosen amounts of water and hydrogen peroxide. The amounts will vary according to the concentration that I am doing for that particular experiment. Below is a table containing the concentrations of my experiments. I will keep the volume of enzymes at 5cm3 for each experiment. I will keep the volume of substrate solution at 10cm3 for each experiment. * I will then add the distilled water to the hydrogen peroxide to get my concentration of substrate. * I will fill up the 100ml-measuring cylinder full of water and tip it upside down in the washing up bowl so that the pressure of the water in the bowl holds up the water in the measuring cylinder. ...read more.

Conclusion

My graph reflects just this. This means that I have succeeded in proving my prediction is correct. I have drawn 2 dotted lines on the graph. The first one shows the initial rate of the reaction and the second one shows the final rate. If the reaction did not slow down at the end then the two lines would not have a gap between them. They show how the rate differs from start to finish. At the beginning of the graph up to a point around 24% substrate concentration the graph is straight and it goes through the origin. This shows a steady, proportional increase in volume produced. Above that point (25%), the graph begins to curve so it is here that the increase fails to be proportional. The line curves with a gradually decreasing gradient. I can make a good guess that the line would carry on curving to form a plateau of gradient 0 if I were to extend my graph, however my results were not broad enough to show this plateau. Most of my points seemed to follow the line of the curve with the exception of the point at 40% which I noticed after I had drawn my line was an anomaly. Firstly, the simple increase in volume with concentration can be explained by the collision theory. This tells us that the higher the substrate concentration, the more substrate molecules there are, therefore more collisions can take place over a set amount of time as there is an increased probability that an enzyme and a substrate molecule will collide. The collision theory explains the steady increase in the graph but it doesn't explain why it starts to level off as the concentration increases. Up to 25% concentration the increase is proportional. This is where there are not enough substrate molecules for the catalase to work at a maximum velocity so as I added more substrate, the enzymes worked harder proportionally. At the point where the graph levels off, the reaction is starting to become ENZYME SATURATED. 1 ...read more.

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