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Effect of Substrate concentration on the enzyme catalase.

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Introduction

Sumudu D. Lankatilake L6B Biology Coursework Effect of Substrate concentration on the enzyme catalase Scientific knowledge Enzymes Enzymes are catalysts, that is they increase the rate of a reaction, which would otherwise react very slowly without the presence of an enzyme. The products of reactions, with the use of enzymes, are therefore obtained more quickly. Enzymes have an area on their molecules that have a specific shape in which the substrate molecules can fit into and combine or separate. This site on the enzyme is called the active site. All enzymes are globular proteins and within the cell they have two fundamental roles: * They act as highly specific catalysts greatly speeding up chemical reactions that would be hopelessly slow. * They provide a mechanism whereby individual chemical reactions can be controlled, the available quantity of an enzyme determining the rate of the corresponding action. Enzymes are made up of chains of amino acids that are twisted and folded to compact rounded molecules that are called globular proteins. The specificity of an enzyme reaction occurs because each enzyme has a definite three dimensional shape that is complementary to the substrate molecule. The first step in the reaction is forming a specific association of the molecules called the enzyme substrate complex. This is because the active sites of the enzyme and substrate molecules match each other but must collide in the correct orientation. The enzyme and substrate interact in such a way that a chemical reaction takes place and the specific products are formed. The products leave the enzyme molecule and the enzyme molecule is available to be reused. This mechanism is known as the lock and key hypothesis. Another concept is the "induced fit" theory where the configuration of the enzyme becomes altered as the substrate binds at the active site. At the same time the binding process changes one of the chemical bonds in the substrate molecule so that a chemical reaction occurs. ...read more.

Middle

With using potatoes or liver etc. you can't be sure if the concentration of catalase is constant. One potato may have more catalase than another. This could lead to inaccuracies and thus an unfair test. Other factors needed to ensure a fair test is keeping the temperature, air pressure, volume of hydrogen peroxide, volume of yeast, concentration of yeast, type and batch of yeast constant. The reading taken from the gas syringe must be read perpendicular to the graduation to avoid a parallax error and retain the accuracy of the experiment. The reliability of the experiment was conserved by repeating the experiment. In this case the experiment was repeated three times with a similar pattern of results. The control is the use of distilled water (a concentration of 0%) to show that it is indeed because of the enzyme catalase acting on the hydrogen peroxide. Safety A strong solution of hydrogen peroxide can cause burns so gloves should be worn for a strong concentration. A pair of safety glasses should be worn at all times cause hydrogen peroxide can irritate the eyes. For the experiment we only used 20 volume hydrogen peroxide which is a relatively safe concentration. Although eye protection must still be worn. Pupils should check that over frothing does not occur during the experiment. If swallowed mouth should be washed and a glass or two of water drunk. Seek medical attention. If liquid gets in your eyes flood the eye with gently running water for 10 minutes. Seek medical attention. If spilt on skin or clothes. Flood area with large quantities of water. Remove and soak contaminated clothing. If lasge area is affected or blistering occurs seek medical attention. If spilt... wear protection and cover with mineral absorbent and clear up into a bucket. Rinse several times. Add water to dilute thoroughly and wash down the drain. Dispose of by diluting thoroughly in water and pour down the drain. ...read more.

Conclusion

If I got similar results with different techniques then it would further confirm my results of the experiment. Improvements A number of improvements could've been made. The experiment could have been repeated several times more so that the errors in a single experiment can be compensated for by other experiments and a better overall result would have been obtained. I could have used more concentrations of hydrogen peroxide to get a larger number of results for each concentration and thus a better curve on the graph. The concentrations could have been between the concentrations already used such as 1.5% and 2.5% etc. If higher concentrations of hydrogen peroxide were available I could have continued the experiment right to the saturation point but we were limited to a 6% concentration. Someone else could have read the graduation while I looked at the time to get a more accurate reading of the volume of oxygen obtained, as the gas syringe was constantly moving during the experiment, or an even better method would be to use an electronic instrument to measure the volume of the oxygen more accurately. It could also be connected to a data logger to measure the corresponding time as well. One method could be to measure the pressure changes caused by oxygen in a closed system electronically. I could have used a buffer solution to ensure that the PH is constant. The experiment could have been carried out in a water bath to keep the temperature constant because small differences in temperature can significantly affect the rate of reaction. A Haemocytometer could have been used to measure the concentration of the yeast to see if it was absolutely constant. Conclusion Hence the hypothesis of substrate concentration increasing the rate of a catalysed reacyion till the end point is confirmed. In the context of cell metabolism, these reactions are potentially important in the controlling different types of reaction. In many cases the substrate concentration is a very important factor in the rate of a reaction but from this experiment we can also see that for some other reactions enzyme availability is also critical. ...read more.

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