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Experiment To Investigate The Effect Of Concentration On An Enzyme Based Reaction.

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Autumn 2003 Experiment To Investigate The Effect Of Concentration On An Enzyme Based Reaction Aim: To investigate the effect of either enzyme or substrate concentration on the rate of decomposition of hydrogen peroxide using catalase enzyme. Introduction: (information obtained from "OCR Biology 1", "Advanced Biology" & "Hutchinson Dictionary of Science") An enzyme is a protein molecule that speeds up chemical reactions in all living things. Without enzymes, these reactions would occur too slowly or not at all, and no life would be possible. Enzymes, for example, are needed for respiration to occur. Enzyme molecules function by altering other molecules, known as the substrate, to form a new product. They combine with the substrate molecules to form a complex molecular structure in which chemical reactions take place before the enzyme, which remains unchanged, separates from the product of the reaction. There have now been over seven hundred different enzymes identified by scientists, which have varying turnover numbers between 100 and several million. This 'turnover number' refers to the number of substrate molecules that one of the enzyme molecules can turn into a new product in one minute. Enzymes are classified into several broad categories, such as hydrolytic, oxidising and reducing, depending on the type of reaction they control. Hydrolytic enzymes accelerate reactions in which a substance is broken down into simpler compounds through a reaction with water molecules, oxidising enzymes, known as oxidisers, accelerate oxidation reactions and reducing enzymes speed up reduction reactions, in which oxygen is removed. The enzyme used in this experiment, catalase, occurs naturally in the tissues of most living organisms and can be found in the liver of the human body. It is present in the peroxisomes, which are micro body organelles that house various oxidation reactions in which toxic peroxides are generated as side products, of nearly all aerobic cells. It serves to protect the cell from the toxic effects of the side product, in this case hydrogen peroxide (2H2O2), by catalysing its decomposition into oxygen and water and is the fastest known enzyme with a turnover number of 6 million. ...read more.


Inhibitors therefore slow the rate of reaction. They should not have affect on 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 the Catalase, they were not included in this investigation and therefore would not have affected the rate of reaction and the results of this experiment. * Pressure- altering the pressure of the solutions would affect the rate at which they react. For example, if the pressure was increased then the substrate and enzyme molecules would be forced together, therefore the rate of reaction will increases as the molecules will be encouraged to collide with each other, however this will only happen up to a certain point as the molecules can only be induced to collide a certain amount, any point beyond this will have no affect on the reaction rate. In my experiment the conditions in which I carry out the experiment will be kept the same, therefore the pressure should not alter and will remain constant. The variable will be: Enzyme Concentration - Provided there is an excess substrate, an increase in enzyme concentration will lead to a corresponding increase in rate of reaction. Where the substrate is in short supply (i.e. it is limiting) an increase in enzyme concentration has no effect and the rate of reaction will no longer increase. I will vary the enzyme concentration by altering the volume of water added to the Catalase, in the reaction (by dilution of the hydrogen peroxide). DIAGRAM OF APPARARATUS: Once all the equipment had been collected it was assembled. The Hoffman's clamp was attached tightly to the clamp stand to make sure that the equipment would be held securely. ...read more.


So at higher concentrations of enzyme solution, the oxygen is given off more rapidly because there are more enzyme molecules working on substrate molecules in a second. PRELIMINARY METHOD: Before the actual experiment was performed, a preliminary experiment was carried out in order to determine certain factors of the experiment, which would need to be researched in order to make sure the main experiment would produce accurate results. These factors included: * A suitable range of concentrations of yeast solution to test. The concentration levels can neither be too high or too low. If too much water were added to the yeast then solution would be too dilute causing the reaction to be slow due to a lack of collisions taking place and this would waste too much time, however if not enough water were added the yeast may be too concentrated making the reaction rate much quicker, this would result in a lack of time to record the events of the reaction as it would have taken place far too quickly. * A suitable concentration for the substrate also had to be determined, as it would also contribute to a change in the rate of reaction. * The controlled variables, for example pH and temperature, will also need 2 be determined, as they may have an effect on the reaction rate, so may therefore give inaccurate results when altering the enzyme concentration levels. * Another area that will need to be determined is the apparatus that will be used throughout the experiment. This will need to be suitable and enable the experiment to be carried out effectively and correctly in order to produce results, which are both reliable as well as accurate. Firstly, the following equipment was collected and set up to begin evaluating the effectiveness of the apparatus and the other factors that would need to be considered during this preliminary experiment: * Hydrogen peroxide (20 volume) * Yeast solution (10%) * Hoffman Clamp * Clamp stand * Hypodermic needle and bung * Plastic container * 5cm3 syringe * Delivery tube * Measuring cylinder * Stop clock Test tube ...read more.

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