Biology Coursework Investigation

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Biology Coursework Investigation

Aim

        The aim of my experiment is to investigate how long is needed to digest starch using the enzyme amylase at different temperatures.

Introduction

I am investigating the time needed for enzymes at different temperatures to digest starch. Enzymes are small protein molecules made in the pancreas and stored in the stomach. They are a biological catalyst that means they increase the rate of reaction in digestion. For enzymes to digest they need to be denatured; this is the term used to describe when enzymes are heated to reach their optimum temperature; when the enzyme is heated over its optimum temperature its bonds are broken and the shape of its active site changes therefore preventing the substrate from fitting into it, as each substrate is specific to one enzyme it will therefore stop reacting. After the enzyme is denatured it can never return to its previous state and because enzymes have a high specificity they can only catalyse one reaction. I am going to test for starch using iodine, when the iodine turns brown this will indicate that the starch is digested.

 

Variables

           A variable is anything you can measure or change in an experiment. In this investigation there are certain variables, which must be taken into consideration before carrying out the experiment. These include:

  • The pH of the experiment (input variable) – If the pH is changed this will dramatically affect your overall results. I found this out through the preliminary work. As the pH of an enzyme increases (becomes less acidic) the enzyme activity increases until there is an optimum pH. As pH increases further (becomes more alkaline) the activity decreases. At very low pH and very high pH, the enzyme is denatured and does not work.

  • The type of enzyme (input variable)– The type of enzyme you use is also very significant to your results. This is due to the fact that different types of enzymes have different optimum temperatures and therefore are denatured at different temperatures.

  • The temperature of enzyme (input variable) - This is another input variable which if changed will alter your overall results.  This is due to the fact that enzyme activity increases as temperature increases, until an optimum temperature is reached; then the activity rapidly decreases until the enzyme no longer works. At high temperature the enzyme is denatured this is normally 50°C and above. When an enzyme is denatured its shape changes so that the active site shape is changed permanently and the enzyme does not work. In conclusion, it is obvious that altering the temperature of the enzyme will dramatically change your results.

  • The temperature of enzyme and starch (input variable)- As you increase the temperature the rate of reaction increase. This is because when the particles are heated they gain kinetic energy and so vibrate and move faster than before. This would increase the amount of successful collisions; therefore making the reaction faster and changing your results.

  • Sweetness of the solution (output variable) – This is an output variable (it can be measured). When mixed with the amylase solution starch will break down into the sugar, maltose. This tastes sweet and so by tasting the solution you can guess how much maltose there is and compare it against the other temperatures.
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- Time taken for the starch to be broken down (output variable)

          In this particular experiment we will only be changing one of the input variables – temperature. The rest will be controlled in order to make it a fair test. The output variable that we will measure will be the time taken for amylase to digest the polysaccharide – starch.

Prediction

I predict that the amylase will break down the starch most effectively at 40oC, and with decreasing efficiency towards 0oC, at which time the amylase would be unable to break down ...

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*** The candidate has submitted an incomplete report. This report does not contain the candidate's experimental results table, although the results are discussed and evaluated and a graph has been plotted. Planning The student planned a simple procedure and used suitable equipment. The student planned to take a suitable range of five temperatures and to repeat these readings but several key variables were ignored in the planning stage. To improve : There were many scientific inaccuracies in the background material. The student would have benefited from widening the research to include appropriate books and textbooks and selecting relevant material. The risk assessment could have been presented more clearly in a table and the concentrations of the solutions used should be stated. Carrying Out Although the student discussed the results these were not present in the report. All raw data for pilot and main experiments are expected to be seen recorded clearly in a table with the correct headings and units. The student would gain no merit for this section. Analysis and Evaluation There is a graph plotted but it is not clear whether this is of the candidate's results. The graph should be included in the conclusion of the experiment not at the end. The student has identified a trend in the data and partly explained this using relevant scientific background theory. The student has commented on the reliability of the procedure and suggested some ways of improving the reliability.