Independent While the reaction is taking place the hot

Independent variable: The pH level for each reaction, will be testing pH of 2,4,6,7,10,12,14

Dependent variable: the rate of reaction between the amylase enzyme and starch molecules, the time taken for the complete hydrolysis of starch will be determined by observing when the blue-black colour of the iodine and starch mixture disappears.

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Controlled variables:

·      Temperature: must remain constant for all trials as a change in this variable can vary results. Enzymes are highly sensitive to temperature changes as any increase in temperature increases the reaction rate as molecules have more kinetic energy and thus a higher chance of successful collisions. In efforts to mimic the conditions of the human body, all trials will be conducted at a temperature of 37oC (body temperature). Since I cannot be provided with an incubator, a hot water bath will be prepared using a hot plate in which the test tube containing the starch and iodine solution will be placed. As soon as the solution reaches the desired temperature, the solution of amylase in a specific pH buffer will be added. While the reaction is taking place the hot plate will be continuously adjusted to maintain the temperature.

·      Volume and concentration of amylase: must remain constant for each repeat of the experiment as any changes to these two variables could make the enzyme more or less effective at its hydrolysis reaction. For example, an increase in volume would mean there are a greater number of available active sites for starch molecules to bind to and so the chances of successful collisions greatly increase. A change in concentration could result in amylase being able to catalyse the reaction at a faster or slower rate.

·      Volume and concentration of starch: must also remain constant for all trials. For example, an increase in volume means the amylase will have a greater number of starch molecules to hydrolyse which can increase the time it takes for the reaction to complete. A change in concentration will impact the reaction velocity as the substrate molecules will have a greater or lesser ability to collide with enzyme molecules.