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the effect of substrate concentration on the rate of an anzyme reaction

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´╗┐This document was downloaded from Coursework.Info - The UK's Coursework Database - http://www.coursework.info/ The effect of substrate concentration on the rate of an enzyme reaction Pilot and main experiment Aim: This is an experiment to investigate how the concentration of the substrate Hydrogen Peroxide (H2O2) affects the rate of reaction of the enzyme Catalase, in yeast cells. Background theory: An Enzyme is a globular protein, which is capable of starting a chemical reaction, which involves the formation or breakage of chemical bonds. The feature of Enzymes are to speed up the rate of reaction, it lowers activation energy (the higher the activation energy, the slower the reaction will be) , denatures if the temperature is too high and is a biological catalyst. Enzymes increase the rate of biochemical reaction to more than a billion times their normal rate, without being changed or used in the reaction. This is why they can be reused and even small concentrations of enzymes can be very effective. Enzymes cannot make reactions occur which otherwise wouldn't happen, and they do not alter the final amount of product formed. In addition they are very specific and they won't catalyse just any old reaction, only those which are suited for the enzyme. Enzymes formed and retained in the cell are known as intracellular enzymes, like Catalase, and may occur either in the cytoplasm or the nucleus of the cell. Certain other enzymes produced in the cell are packaged to be secreted from the cell, and work externally, including most digestive enzymes. These enzymes are called extracellular enzymes. Furthermore all enzymes contain an active site, a depression in the enzymes molecule, where a specific substrate molecule can fit into exactly and bind to. The active site is small and usually 2 to 20 amino acids. All enzymes have a substrate molecule, which is the same shape as its the active site. ...read more.


Once the number of substrate molecules added is more than the number of active sites which are unfilled, then the rate of reaction will no longer go up. When this point is reached, adding extra substrate will make no difference to the rate of the reaction. This is because the maximum number of reactions are taking place at once so any more substrate molecules have to wait until some active sites are no longer in use. In addition I would predict that the amount of oxygen evolved would double from the Hydrogen Peroxide concentration 5 to 10 moldm and also a doubling from 10 to 20 moldm . Apparatus list: item quantity Concentration and volume accuracy 50cm Burette 1 50 cm of distilled water 0.05 cm Beaker 4 50 cm and 100 cm - Boiling tube 1 - - Clamp stand 1 - - Thermometer 1 - 2 C Stop clock 1 - 1 s 10 cm syringe 2 10 cm 1 cm 1.0 ml syringe 1 1 cm of yeast for every experiment 0.1 cm Distilled water Circa 150 cm pH 7 - 20 % H2O2 Circa 150 cm 20% concentration - Stopper 1 - - Delivery tube 1 - - Yeast 10 cm 10% concentration , 1g every cm - Text marker 1 - - Goggles 1 - - Table to show reasons for choice of apparatus: item What it is used for Reason for choice Burette To collect the volume of oxygen evolved in 10 seconds It is very accurate Beaker Contains solutions Easy to use and is able to contain large amount of solution Boiling tube To contain the substrate and this is the place where the enzyme- substrate reaction occurs It is larger than the normal test tube Clamp stand To hold the burette upside down in place It can hold the burette horizontal Thermometer To measure the room and water temperature I can easily read the temperature and see a change in temperature Stop clock To time the ...read more.


The hydrogen peroxide would be more diluted, so that the amount of oxygen produced would be less than expected middle Wash it out and then dry it properly It would be an error in measurement You could push the yeast to much into the boiling tube so that it splashes next to the boiling tube The whole experiment would be wrong and the values you get for the amount of oxygen would be an anomalie Very high Fill the yeast into the boiling tube very carefully Incorrect working Loss of oxygen gas I would have measured less oxygen high To use better sealing, eg use a better stopper This would be an error in measurement I have no anomalous results and my experiment went well. There were no major errors except the changing of the temperature which had to be noticed. After noticing i changed the normal tap water into cooler water to make it a fair test. I can be confident of my results because there are no anomalous and there was no great inaccuracy. In another experiment i would have probably used a gas syringe instead of the burette, because it was quite difficult to fill the burette with exactly 50 cm of water and to make sure that no oxygen will be lost. The construction between the end of the burette and the delivery tube was not as accurate as it could be and maybe some oxygen was lost there. My results are all very similar at the same concentration and are precise and reliable. The standard deviations of the measurements are are all similar small, but it would have been more accurate to use more readings for same concentrations to increase the significance of the experiment. Further it would be good to have results with the volume of Hydrogen Peroxide using 30 or 40 cm to make sure my experiment was correct and the results are as expected ( the curve of formed oxygen levels off at higher substrate concentration). ...read more.

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