Affects of Temperature On the Digestion of Starch.

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AFFECTS OF TEMPERATURE ON THE DIGESTION OF STARCH

PAUL MITCHELL

SCIENCE COURSEWORK

Affects of Temperature On The

Digestion of Starch

  • Introduction

For my experiment, I will be looking at enzymes; more specifically, the enzyme amylase.  Amylase breaks down starch into glucose.  I will be looking at how temperature affects this conversion.

Enzymes exist in all living things. They are composed of polypeptide chains of amino acids and are produced in living cells. Each cell contains several hundred enzymes, which catalyse a vast number of chemical reactions.

Enzymes are known as ‘Biological Catalysts’ as they dramatically affect the rate at which reactions occur within living organisms, without being 'used up' or effecting the reaction in any other way. Enzyme catalysis saves the need for an increase in temperature in order to speed up reactions within living things. Such an increase in temperature would be lethal to the organism.  Enzymes only control the rate of one specific reaction inside the body, as only one specific substrate can fit into its active site; therefore we say the enzyme is specialized.

There are two main types of enzyme:

  • Intracellular enzymes, which control reactions that occur inside cells.
  • Extracellular enzymes, which control reactions that occur outside cells

All enzymes are affected by temperature and pH.  They have an optimum range of the two, and anything outside this range will denature the enzymes “active site.”  The enzymes that are used in reactions inside our bodies have an optimum temperature of 37oC.  The enzyme can withstand a few degrees either side of this temperature; but any higher will cause the protein structure to break apart and stop working, because the bonds that hold the amino acids together are relatively weak; therefore, a high temperature would cause the atoms to excite and the bonds to break.

The enzyme will become denatured permanently and no longer functional.  The optimum pH for an enzyme depends upon where about in the body it is working.  Generally, most enzymes have an optimum neutral pH of around 7, but enzymes that work in the stomach, for instance, have a much lower optimum pH of 2 due to the acidic environment.  

  • Prediction:

I predict that as the temperature increases, so will the rate of the reaction.  I think this because when heat is applied, it excites the particles more and as a result, they collide faster and so the reaction rate increases.  When a particular temperature is reached, I think the rate of reaction will dramatically decrease because the amylase is working outside its optimum temperature range.  Usually a rise of about 10oC will double the rate of reaction.  After the enzyme reaches its limit, which I predict to be 40oC, I think the reaction rate will decrease rapidly and then stop.  I think this because the enzyme has become denatured and the bonds holding the enzyme together have started to break; therefore denaturing the active site.

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  • Equipment List:

Variables:

To keep my experiment as fair as possible and to achieve the best possible results, I will keep the following aspects of my test identical:

Amount and concentration of starch solution, Amount and concentration of amylase solution, amount of iodine solution, amount of benedict’s solution added and pH.

The only variable in my experiment will be the temperature change, as this is the objective of my test.

  • Safety Precautions:

Throughout my experiment I will be handling chemicals; some of which are dangerous.  I will also be using a Bunsen burner throughout the ...

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