Biology Coursework Enzymes

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Mustafa Saai, 11P

Biology Coursework

Aim

To investigate how starch concentration affects an amylase-controlled reaction.

Introduction

An enzyme is a protein with a special shape, which catalyses or speeds up chemical reactions inside our bodies. However not all enzymes are proteins. The enzyme amylase that I will be using throughout my investigation to find out how starch concentration affects an enzyme controlled reaction is found in saliva in the mouth and also in the small intestine. Inside the body the enzyme amylase is used to break down the substrate starch into simple sugar (maltose), which is soluble in water. Enzymes are crucial to the existence of humans as it speeds up chemical reactions inside the body, which would be too slow in the absence of enzymes. Enzymes themselves only catalyse chemical reactions and do not alter the actual reaction, they also increase the rate of reaction.

Enzymes have many properties which if affected can change the outcome of reactions taking place. When enzymes react the same end product is always formed.  Enzymes themselves react best at the optimum temperature of 36.7 °C, as that is the general temperature of our bodies. Also enzymes have optimal pH levels as well at which they react best. The pH at which enzymes work best at is 7 (neutral). However exposure to heat over 40 °C or extreme pH (acid or alkali) can denature the enzyme, which will mean that they can no longer act as a catalyst for the reaction. Temperatures under 36.7 °C will not denature the enzyme but the reaction taking place will be considerably slower.

The lock and key theory is a theory in biochemistry that looks at why enzymes catalyse reactions. The theory states that all enzymes have a unique shape and have a special active site on which the substrate attaches itself to and allows the enzyme to begin breaking down the food into products (nutrients). The active site breaks down the substrates by affecting the substrates bond of electrons. Once the enzyme has broken down the substrate into products the enzyme can then act on the next substrate as enzymes can be reused.

The collision theory is also another theory that states how chemical reactions occur and the reason why the rate of reaction differs. In order for a reaction to take place particles must collide. When successful collisions take place they cause some chemical changes because of the impact caused by the collision causing the bonds of some substrates to break resulting in a “successful collision”. However only a certain percentage of collisions result in chemical change. In order for chemical reactions to take place the substrate particles need energy to break the barrier and result in a product. This is called the activation energy

Enzymes are also used in many day-to-day products such as; washing powders, the clarification of juices and are also used in the process of fading jeans.

Preliminary Work

Before I begin my actual experiment I will conduct a preliminary experiment to gain an insight into how the enzyme amylase breaks down the substrate starch. This preliminary work will give me experience and extra information about how amylase reacts with starch.

Apparatus

The apparatus I will use to conduct my preliminary work will be:

  • Amylase solution (3%)
  • Starch solution (5%)
  • Iodine
  • Boiling tube
  • 10ml Measuring cylinder
  • Spotting tile (with 12 wells)
  • Graduated pipette
  • Digital Stopwatch
  • Safety Goggles

Method

I will use this method to conduct my preliminary work efficiently and accurately:

  • Firstly I will place 2 drops of the iodine solution into each of the 12 wells of the spotting tile using the graduated pipette.
  • Secondly I will place 2 drops of the starch solution using the graduated pipette into the first well. (As the iodine solution reacts with the starch to produce a blue/black colour this will help me compare what reaction has taken place with the starch and amylase reaction.)
  • Thirdly I will measure out 5ml of the 5% starch solution with the 10 ml measuring cylinder and add it into a boiling tube.
  • Fourthly I will measure out 1ml of the 3% amylase solution with the cleansed 10ml measuring cylinder.
  • Fifthly I will add the measured amylase into the boiling tube with the starch solution and immediately start the digital stopwatch; also I will instantaneously add 2 drops of the amylase/starch solution into the second well of the spotting tile.
  •  Finally I will add two drops of the starch/amylase solution every 30 seconds to the next well until there are no remaining wells.
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Results

With the results I got I was able to draw a table, which displays the resembling colours of the starch and amylase solution reacting with the iodine and also displaying the times and any other relevant information.

 

Conclusion

From my preliminary work I was able to identify any problems I might have encountered and also I gained an insight into how amylase breaks down starch.. I noticed that the method I used in my preliminary work was not very reliable, accurate and would ...

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****A well constructed procedure demonstrating good scientific knowledge. Planning The experiment was trialled and the procedure modified. There was a qualitative prediction supported by scientific evidence. The main error was the inclusion of an apparatus list which belonged to an entirely different experiment. Carrying out The candidate has presented the results of the pilot experiment and main experiment in a fairly clear and organized way. The range and number of repeats was acceptable. Analysis and Evaluation There was evidence of good processing of results- calculations of mean and rate of reaction. The conclusion was explained well using scientific theory. The student has considered the reliability of the evidence and made some sensible suggestions to improve the method. It might have been improved if another method could have been suggested such as the inclusion of a buffer to maintain pH and the measuring of colour using a colorimeter. The student does not have to have the equipment available to carry out a different technique.