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Determine how the substrate concentration affects the activity of catalase in hydrogen peroxide.

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Introduction

The aim of this experiment is to determine the substrate concentration affects the activity of catalase in hydrogen peroxide. Enzymes are biological catalysts; they are globular proteins and allow many chemical reactions to occur within the homeostasis constraints of a living system. Enzymes function as organic catalysts. A catalyst is a chemical involved in, but not changed by, a chemical reaction. Many enzymes function by lowering the activation energy of reactions. By bringing the reactants closer together, chemical bonds may be weakened and reactions will proceed faster than without the catalyst. The shape of the protein determines the functioning of the enzyme. The arrangement of molecules on the enzyme produces an area known as the active site within which the specific substrate(s) will "fit". It recognizes, confines and orients the substrate in a particular direction. Many enzymes require the presence of an additional, nonprotein, and cofactor. Some of these are metal ions such as Zn2+ (the cofactor for carbonic anhydrase), Cu2+, Mn2+, K+, and Na+. Some cofactors are small organic molecules called coenzymes. The B vitamins are precursors of coenzymes. * Thiamine (B1) * Riboflavin (B2) * Nicotinamide 2 H2O2 ----> 2 H2O + O2 (Hydrogen peroxide ----> water + oxygen) Coenzymes may be covalently bound to the protein part (called the apoenzyme) of enzymes as a prosthetic group. Others bind more loosely and, in fact, may bind only transiently to the enzyme as it performs its catalytic act. Hydrogen peroxide is chemical compound, H2O2, a colourless, syrupy liquid that is a strong oxidizing agent and, in water solution, a weak acid. It is miscible with cold water and is soluble in alcohol and ether. Although pure hydrogen peroxide is fairly stable, it decomposes into water and oxygen when heated above about 80�C; it also decomposes in the presence of numerous catalysts, e.g., most metals, acids, or oxidizable organic materials. A small amount of stabilizer, usually acetanilide, is often added to it. ...read more.

Middle

at room temperature to maintain a constant temperature throughout the experiment pH Level Enzymes work at an optimum pH just like temperature. If the pH changes it affect the hydrogen bonds of the enzymes casing them to denature temporarily which causes them not function properly This will have to remain constant otherwise it will affect the rate of reaction as the active site of the enzyme can change, so I will control it by using only distilled water as it is pH neutral and will not slow down the reaction. The Enzyme Inhibitor Level For the experiment to be fair there has to be no inhibitors, which can take over the active site not allowing the enzyme to break up the substrate, therefore slowing down the rate of reaction. Also the inhibitors can join onto another part of the enzyme which can cause the shape of the enzyme to change not allowing the enzyme to work To make sure that the reaction is not affected by inhibitors I have decided to use distilled water instead of tap water as it may contain impurities which may contain substrate-like inhibitors whereas distilled water is clean and will not contain such impurities To make sure that the final experiment is well thought of and planned I decided to do a preliminary experiment which will enable me to complete the final experiment to the best accuracy and precision, which I may not have thought of beforehand, which could lead to the experiment not being a fair test, leading to imprecise results. My preliminary experiment is very similar to the actual experiment apart from the things that I learn that I need to improve on. Safety is a key issue that must be considered prior of proceeding with the experiment. If these certain safety rules are not considered they could consequence in inaccurate results due to being unprepared, you have a good chance of wasting time and making a mistake. ...read more.

Conclusion

it also acts as a plug This would stop gas escaping so it is possible to measure the correct amount of gas collected so I get a accurate reading at 30 seconds 3 Fluctuating temperature at room temperature. At the beginning of the experiment the room temperature was less and then it increased because there were many people in the lab slightly increasing the heat This will act as activation energy causing the rate of reaction to increase as the substrate and enzyme molecules are more likely to collide successfully because of increased kinetic energy I could proceed with the experiment in a water bath which will be a constant temperature and is less likely to fluctuate This will lead to no activation energy which will be a fair test throughout, leading to more reliable results 4 The percentage error of the pipette When collecting the solutions need for my experiment I could have collected a incorrect amount, this could ultimately cause a unfair test and affect my results Use a piece of equipment with less divisions such as a gas syringe This will give a more accurate volume of gas and it is easier to read of this apparatus as it more clearer 5 When reading off the pipette bubbles formed at the surface of the water which made it difficult to read the decrease in water, so sometimes I had to estimate it as it kept lowering The number, which I read, could have been incorrect by up to 0.5. ml which could affect the trend on the graph giving an anomalous result Again a gas syringe could solve this problem as it is quite wide allowing space for the bubbles to pop, making it easier to read If I can get clear readings it is more likely that my results have less of an error which could prevent any anomalous results 6 7 8 9 10 * Enzymes: http://www.ultranet.com/~jkimball/BiologyPages/E/Enzymes.html * Cambridge Advanced Sciences Biology 1 Nisha Patel 12E Ms. Sharma 2 ...read more.

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