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Investigate the factors affecting the rate of breakdown of sucrose by the enzyme sucrase (invertase).

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GCSE Biology Coursework Investigate the factors affecting the rate of breakdown of sucrose by the enzyme sucrase (invertase) Avninder Gidar Planning Definition of enzyme An enzyme is a biochemical catalyst that enormously accelerates a chemical reaction. Enzymes are complex protein molecules highly specific to particular reactions. (Taken from the Collins Dictionary of Medicine) How enzymes work Enzymes have an area - usually thought of as a pocket-shaped gap in the molecule - which is called the active site. The substrate (or substrates) fits/fit into the active site, but enzymes are specific so only a certain substrate will fit a particular enzymes active site. There are several types of enzyme which contribute to different types of biochemical reaction. The enzyme speeds up the process of conversion of substrates into products. Although the enzyme joins with the substrate for a short while, the enzyme and substrate split apart afterwards, releasing the enzyme. Thus the enzyme is not used up in the process unlike the substrate, so it can continue to react if more substrate is provided. The enzyme I am investigating and what it does I am investigating the rate at which the enzyme sucrase breaks down its substrate sucrose. Sucrose is a type of sugar used by many plants as a convenient form in which to move carbohydrate around the plant i.e. from leaves to roots. Each sucrose molecule consists of two single glucose molecules joined together and the sucrose must be broken down before it can be used to provide energy through respiration. The enzyme sucrase is used to break down the sucrose molecules into glucose so they can be respired. Factors that effect the rate at which enzymes breakdown There are many factors that affect the rate at which enzymes breakdown their substrate for example - * ...read more.


At higher temperatures these bonds literally get shaken apart and the three-dimensional structure of the protein destabilises. This is called denaturisation and will dramatically slow down the rate as the substrate no longer fits the active site of the enzyme. Optimum temperature for sucrase = 37�C My Factor I have chosen to make my variable factor Temperature. All other factors must be kept the same (how is stated later). I will vary the Temperature by the use of a water bath. This will help maintain the temperature required at a constant during each experiment. Both the enzyme and substrate will be heated in the water bath to the temperature required for about five minutes so that the breakdown occurs at the desired temp. The rest of the experiment will take place inside the water bath to ensure a constant temperature is kept. I know from research the optimum temperature for sucrase is 37�C. I will use this value to concentrate some values of my range. (http://www.usdsu.org/faculty/madsens/powerpoints/Spring%202004/Lecture%20stuff/Lecture%2010%20Chapter%2021%203%2030%202004%20%20ALL%20sections.pdf) - Research page. Temperature Range I will be looking at a wide spread of temperatures to help make my results more reliable. My range will be: 10�C 20�C 30�C 34�C 37�C 40�C 50�C 60�C I believe that this range is wide enough to find the temp at which sucrase denatures and find the optimum. Rate I will find out the rate buy using 1/T. Therefore I will need to know the time it takes for the total breakdown of sucrose. This will be achieved by timing how long it takes for a clinistix to change colour from pink to blue i.e. to show when the end point is and glucose is produced. Maintenance of other factors It is very important to keep ALL other factors the same to achieve more accurate and reliable results. ...read more.


Looking at the graph there was only 1 apparent anomaly which is at 44�C. The rest of the results follow the line of best fit accurately. From the table there is not a lot of deviation between replicates so I believe the results were quite accurate. I recon my experiment was a fair test as all of the factors were maintained accurately I believe 4 replicated were enough to get a reliable average and spot any anomalies. The range could have been wider after the optimum to determine the point at which the enzymes denatured more accurately. Problems During the experiment there possibly was some unwanted mixing of solutions, which could explain why the 44�C result was consistently to fast in all the replicates. The cleaning of test tubes was not very good; some residue of enzyme could have been left over in a test tube where sucrose was measured out into, starting breakdown. It was hard to get the same colour on the clinistix for the end point There were two different types of clinistix (one which reached end point much faster) so using the wrong clinistix could effect results drastically. Improvements Use a wider range of temperature at he optimum and after to accurately determine the denature point Use a burette to accurately measure out solutions Have the two solutions on different sides of the room with its own set of equipment to stop any contamination of solutions (the accidental addition of sucrase to the sucrose source could seriously effect the results as breakdown will already occur). Use a magnetic stirrer to evenly mix solutions. Use a bigger concentration to make the time to end point of clinistix more, so results are more accurate times. Use a colorimeter to determine the colour of clinistix at the end point accurately. - 1 - ...read more.

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