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Activity of starch synthase enzyme.

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Biology Experiment Report --Activity of starch synthase enzyme Introduction Enzyme is a protein that acts as a catalyst in biochemistry reactions. Enzymes speeds up biochemical reactions by lowering the activation energy-the minimum energy required for a chemical reaction to take place. With the presence of enzyme, the rate at which the reaction proceeds to form the product can greatly increase by a factor of up to 1020. Enzymes have several important properties: * They are specific. Each enzyme is specific to a particular reaction or group of similar reactions. For example, trypsin cuts an amino acid chain at a point between arginine and lysine, and nowhere else; amylase only attacks 2-glycosidic bonds but not other bonds. This can be explained by the 'lock and key hypothesis': each enzyme has an active site-the site on the surface of the enzyme molecule that binds the substrate molecule. The size, shape and chemical nature of the active site corresponds closely with a particular substrate molecule, so they fit together like a key fits into a lock, which means other substrates cannot react with the enzyme. * They have an optimum PH and temperature under which they can work most effectively. Most enzymes have an optimum PH of around 7 and an optimum temperature of around 30 C to 40 C (e.g. ...read more.


with glucose-a-phosphate at room temperature * Label 8 test tubes to receive 3 cm of 1% glucose-1-phosphate * Label 4 test tubes to receive 3 cm of 1% glucose * Label 12 test tubes to receive 5 cm of standard iodine solution * Label 12 miniature tubes to receive 1 cm of potato extract * When ready to begin the experiment, add 1 tube of potato extract to each tube of substrate. Note the time. * Immediately i.e. zero time tip one tube of the reaction mixture into a tube of iodine. The iodine denatures the enzyme and stains any starch present. * At intervals of 20 minutes tip another tube of reaction mixture into iodine. Repeat for a total of 4 tubes. * At the end of the experiment determine the amount of starch in each tube by reading the depth of colour in the colorimeter. Record the results and repeat the experiment for the other 2 treatments. * Plot light absorption against time for each experiment. The colorimeter consists of a light source, a filter to select the appropriate range of wavelengths, a photocell whose electrical resistance is proportional to the intensity of light falling on it, and a meter. The sample is then places between the filter and the photocell, a simple diagrammatic representation being given below. ...read more.


Accuracy can be improved by using a volumetric pipette. 2. One container was used for all the samples in the same experiment when using the colorimeter, so there were always a few drops from the previous sample left in the container, which might have affected the reading of the next sample. We can wash the container every time before reusing or use a new one for each sample. 3. The biggest source of error in the experiment was time controlling. * In step 6, I was required to immediately tip one tube of the reaction mixture into a tube if iodine. Whether I was slow of fast in this step might have affected the result. * I used a two-handed watch in the experiment, so I was unable to keep the intervals at exactly 20 minutes. A three-handed watch or even a stopwatch would be much more accurate. The method can be improved by interfacing the colorimeter to a computer to obtain a more accurate reading result. A further study could repeat the experiment at different time intervals and longer time, say 10 minutes for 2 hours, to give more data on the production of starch. Also different enzymes and substrates from different types of organisms (e.g. animals and bacteria) could be employed. The effect of different temperature and chemicals (acids and bases and some inhibitors) could be investigated as well. ...read more.

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Here's what a teacher thought of this essay

3 star(s)

This is a well written report that has some good sections. However the investigation itself lacks direction.
1. The introduction is well researched, but the sources need to be referenced.
2. The hypothesis, equipment and method section all demonstrate good practice.
3. The evaluation is detailed and shows an understanding of scientific processes.
4. The investigation itself needs more direction. It would benefit from a preliminary test to determine the optimum temperature before the actual investigation is run.
***(3 stars)

Marked by teacher Luke Smithen 08/05/2013

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