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An experiment to investigate the effect of substrate concentration on the rate of activity of the enzyme Catalase.

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Introduction

An experiment to investigate the effect of substrate concentration on the rate of activity of the enzyme Catalase PLANNING Aim: This is an experiment to examine how the concentration of the substance Hydrogen peroxide (H2O2) affects the rate of reaction of the enzyme Catalase. The main purpose of this reaction is to find out how; by varying the concentration of substrate (H2O2) the rate of enzymatic activity of the enzyme catalase (which is present in liver) is affected. The rate of this enzyme-controlled reaction can be measured by the amount of oxygen (O2) given off compared to the amount of time it takes to fill the entire volume of the gas syringe. Scientific Knowledge We know that an enzyme is a protein which serves as catalyst - a chemical agent that changes the rate of reaction without itself being consumed by the reaction. Each different enzyme acts upon a chemical substance called a substrate, which fits into the active site of the enzyme like a lock would into a key (lock and key mechanism), during the reaction products are formed. A Catalase enzyme serves to protect the cell (e.g. liver or potato cells) from the toxic effects of hydrogen peroxide by catalyzing (breaking it down) into molecular oxygen and water - O2 and H2O.

Middle

away from the active site - this action alters the shape of active site so that the substrate is unable to occupy it and the enzyme cannot function properly. The type of molecule which attaches itself away from the enzyme's active site - causing it to not function properly anymore is known as a non-competitive inhibitor. Inhibitors therefore slow the rate of reaction. As none are to be added to this investigation, there will be no effect from inhibition. e) Enzyme concentration - The amount of enzyme available to process the substrate can control an enzyme catalytic reaction. By carrying out this experiment we can investigate how doubling the amount of enzyme affects the enzyme catalysis rate, amount of substrate, and amounts of reaction products. Provided there is an excess in substrate, an increase in the enzyme concentration will lead to a corresponding increase in the rate of reaction. When the substrate is in short supply (i.e. it is in limited quantity) an increase in the enzyme concentration has no effect. Apparatus 1) 250ml conical flask and beakers. 2) 40ml Hydrogen peroxide (start off with 10vol and then the concentration will be varied thereafter) 3) Tongs 4) Distilled water 5) Liver (to be cut up into fine pieces which will weigh 1 gram each)

Conclusion

If the concentration were doubled, I would expect the amount of Oxygen released to be a figure twice as much. From 10vol to 1vol shows a directionally proportional decrease in reactivity rate, after 10vol the rate of reaction slows down. At this point virtually all active sites are occupied making the active sites saturated with Hydrogen Peroxide. With an increase the concentration of Hydrogen Peroxide, the number of active sites increases, hence, makes a more violent reaction (Quicker). The theoretical maximum rate of reaction is when all the sites are being used but in reality this theoretical maximum is never reached due to the fact that not all active sites are being used at the same time. The substrate molecules need time to join onto the enzyme and to leave it so the maximum rate achieved is always slightly below the theoretical maximum. The time taken to fit into and leave the active site is the limiting factor in the rate of reaction. Safety Laboratory coats can be worn during the investigation to prevent chemicals from spoiling clothes. Care was also taken whilst handling the chemicals as hydrogen peroxide is corrosive and very toxic (harmful to the eyes and skin). Whilst using the razor blades, care was also taken to hold them by the handle and not the blade to prevent an accident occurring. Rameez Ali 126PAH

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