In this experiment my aim is to find out at which temperature amylase digests starch the quickest.

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Amylase investigation

Aim:        

In this experiment my aim is to find out at which temperature amylase digests starch the quickest.

Prediction:        

Enzymes are proteins which are made by living cells. Digestive enzymes break down larger molecules into smaller molecules. Enzymes are biological catalysts. This means that they speed up the rate of a reaction without being used up themselves. Starch, protein and fats are quite large molecules and so they cannot pass through cell membranes into the blood. Sugars, amino acids and fatty acids/glycerol are much smaller in size and so are able to pass through the cell membranes. Digestive enzymes work to break down these larger molecules into smaller ones. Enzymes are sensitive to both change in pH and temperature. Thousands of different types of enzymes are found in each cell. Enzymes are quite specific in their action. Each enzyme has an active site. Active sites are different shapes in which only one substrate can fit into. This active site breaks down the substrate into the products. After the enzyme has broken down the substrate it can still work on another part of that substrate and it continues to break the substrate into the products:

For example, the enzyme amylase breaks down starch molecules (substrate) into maltose and other products (products). Amylase can be found in the salivary glands. Amylase breaks down starch into maltose. If the resultant solution is blue/black when added to iodine solution then starch is still present. If it turns red/orange when added to iodine then the starch has been broken down into maltose. Iodine is the test for starch.

        The optimum temperature is the temperature at which the rate of reaction is the quickest. You would expect this temperature to be between 35°c and 40°c. This is because 37°c is body temperature and as amylase is found in the body it will be adapted to this temperature. This means that amylase will be used to these types of conditions and will therefore probably digest starch the quickest. With the temperature at 20°c I would expect the speed of reaction to take longer. This is because it is colder than body temperature and the amylase particles won’t have as much kinetic energy and the particles will be moving less than a hot temperature’s particles. This means there will be less collisions  (as the particles will have less energy to move) between the starch and amylase particles and the reaction time will be slower. With hotter temperatures the particles will have more energy to move and they will move more. Therefore there will be more collisions and the rate of reaction will be quicker. At 30°c the rate will be quicker than at 20°c as it is getting closer to body temperature and the particles are moving quicker. As the temperature gets to around 50°c and 60°c the enzyme will begin to denature. This means that it will stop working and it will take the amylase much longer to digest the starch molecules. The enzyme vibrates more and as it has more kinetic energy there are more collisions. The bonds then break and the active site changes shape. This affects the substrate meaning it is much more difficult for it to interlock into the active site. The time taken is affected and less maltose is produced. This is how an enzyme denatures.  

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        I predict that the shape of the graph to be a U shape as to start with it would take longer because there would be less energy for the particles. As the temperature increases from 20°c and 35°c the graph will continue to curve down as it gets closer to body temperature. I think the optimum of the graph will be around 35°c or 40°c. As the temperature increases from 40°c the graph will gradually curve up as the enzyme begins to denature.

        I can back-up my ideas from a preliminary piece of evidence from the computer simulation ...

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