Experiment to investigate the effect of surface area on the rate of reaction.

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Biology AT 1 – Experiment to investigate the effect of surface area on the rate of reaction.

Introduction.

        Enzymes are proteins that behave like as biological catalysts. They are produced inside the cells of the body. It can never be exhausted and is usually used many times. There are two types of reaction that can occur, anabolic and catabolic.

Anabolic involves the creation of a complex molecule from simpler molecules (e.g. glucose, for storage, is turned into starch for later use, in plants):

        However, catabolic is the directly opposite reaction, breaking complex molecules into simpler ones (e.g. protease enzymes turn proteins into amino acids):

        This theory is called the “lock and key” because it shows how the enzymes are specific to what they can/cannot break down or make molecules. Therefore only one enzyme is able to break/make a molecule due to its structure. Equally, this occurs with the substrate, Catalase. The gap is known as the active site as it is unique to its purpose.

Catalase, as it is very specific, is the only enzyme which is able to break down the substance Hydrogen Peroxide (H2O2). This substance is poisonous and is produced by the body from other reactions; therefore it is important to be rid of this toxin. The only way is by producing Catalase which breaks the H2O2 down into oxygen and water:

                                Catalase

2 H2O2                          2 H2O    +     O2

        

                     For this experiment, I will be investigating this enzyme, not from the body but in potatoes as H2O2 is also produced from cellular reactions.

Variables/Hypothesis.

        There are many variables that affect the rate at which the enzyme reacts, in this case, the rate that Catalase breaks the H2O2 down:

  • Temperature – The optimum temperature at which enzymes react is 37o C, the temperature that our body normally works at. The molecules, from the heat energy, move faster. This increases the enzyme’s rate of reaction and substrate molecules meet quicker, speeding the rate at which the products are formed. Soon the reactions break the hydrogen and ionic bonds, forming water and oxygen.  As the temperature continues to rise, to about 50o C or higher, the enzyme becomes denatured, as it’s shape is altered, not allowing it to break down that specific molecule.
  • Enzyme Concentration – If there is an excess of substrate molecules, with extra active sites available from the enzymes, the more frequent the collisions will be between molecules, increasing the rate of reaction. This is known as the collision theory, in which there is an increased chance of a successful reaction occurring, therefore speeding up the reaction.
  • Enzyme Concentration – Providing there is excess enzyme molecules, the introduction of extra substrate molecules will lead to an increase in the rate of reaction. This is because the substrate molecules will occupy all active sites, boosting the chance of a successful collision.
  • pH – The further the pH is away from its optimum, the slower the reaction will be between the enzyme and substrate. A slight variation from the optimum would denature the enzyme, slowing the reaction.
  • Inhibitors – This could compete with the Catalase enzymes for active sites, thus slowing the rate of reaction.
  • Surface Area - This is the variable that I will be investigating. With a larger surface area, for the enzymes to act on; the more of a chance there will be of a successful collision, and reaction. This will speed up the rate of reaction:
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        The surface area will show how the increasing surface will raise the rate of reaction. I will divide a piece of potato, from one length, into various lengths of equal size but in sections/parts (i.e. 3cm length potato cut into 2 parts of length 1.5cm). I will be measuring the amount of oxygen released from each section of these, breaking down the hydrogen peroxide.

Apparatus List

  • 2 Measuring cylinders – 10cm3 for measuring the hydrogen peroxide and gathering the oxygen ...

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