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To investigate changes in the rate of reaction under different temperatures using yeast.

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Biology project KS4 To investigate changes in the rate of reaction under different temperatures using yeast. Introduction In order to understand the three main concepts: enzyme properties and activity, aerobic respiration and yeast, let us first look at enzyme properties and activity. Enzymes are catalysts and exist in all living things. Catalysts speed up the rate of reaction and each enzyme is catalysed by a specific enzyme. Enzymes are proteins. At this moment in time thousands of reactions are going on in our bodies. Enzymes released into the gut help speed up the digestion of food. Without enzymes, the reactions in your body would cease and you would die. Reactions in plants are also catalysed by enzymes. Plants thrive when there is warmth, there is a limit to the temperature at which they can survive. The rate of photosynthesis increases until the temperature reaches about 40?C. Above 40?C photosynthesis slows down and the stops. This is because important chemicals in the plant are destroyed above 40?C. These important chemicals are called enzymes. Enzymes are also used in industry as they are used in biological detergents and washing powders. They break down foods, blood and other biological substances. These biological detergents are more effected than ordinary because they contain enzymes as well as soaps and detergents. ...read more.


As the temperature rises the particles get hotter. They have more energy and move around faster. Most catalysed reactions go faster as the temperature rises but above 40?C their reaction rate decreases rapidly because the enzymes are proteins and there structure is damaged as the temperature rises above 40?C. This damage to the protein structure is called denaturation. As the protein is denatured, it becomes less and less effective as a catalyst and the enzyme-catalysed reaction get slower and eventually stops. Independent variables My independent variable within this practical experiment is temperature my aim is to raise the temperature of the water baths by 10?C each time and record in cm3 the amount of gas given off per 10 seconds. I will repeat the experiment three times at temperatures of 10?c, 20?c, 30?c, 40?c and 50?c and record the results. The range of the temperatures being taken is 40?c. Dependant Variables My dependant variable will be to measure the temperature with a thermometer in to verify the temperature is correct giving me accurate results. I will also be measuring the volume of O2 given off in cm3 per 10 seconds. I will measure this in cm3 using a syringe body to collect the gas. ...read more.


The rate of reaction did increase between 30?c and 40?c but above forty the rate of reaction decreased. This proved my hypothesis to be correct but not entirely as it didn't double in the rate of reaction. Evaluation In my experiment some of my results didn't quite fit this may have been the cause of poor preparation or the way I carried out the experiment. Some of the problems I found in my experiment were: * I should have let the reaction fully finish so that I could obtain a wider range of results giving me more to work on and adjust. I should have started recording at 5 seconds until 110 seconds. * I should have let the solution warm up while it was sitting in the water bath rather than start straight away. * The recording of data may not have been accurate due to the repeated rising in temperature whilst you are trying to take a reading. This may have been the reason why the results didn't double up. * In a classroom environment people are pushing and shoving and so the solutions may have been mixed causing a difference in results. * I rushed obtaining my results and this may have caused me to predict what should be there rather than what is there. * There was not enough lab equipment as people were taking other peoples apparatus which led to confusion and panic. ...read more.

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