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How enzyme concentration affects the rate of reaction Free essay! Download now

Home > A Level > Biology > How enzyme concentration affects the rate of reaction

How enzyme concentration affects the rate of reaction

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Downloads to date: N/A | Words: 2500 | Submitted: 21-Jan-2009
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How enzyme concentration affects the rate of reaction


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Enzymes are proteins that act as catalysts. They speed up chemical reactions which would otherwise take a very long time. The advantages of enzymes are that they do not get used up in the reaction but stay unchanged. So only a small amount of enzyme is needed as they can be reused. To understand the significance of enzymes in an enzyme-catalyzed reaction some information about how they work must be known.
Enzymes are protein molecules which are made up of amino acids. They have a three- dimensional shape because of the way the amino acids are arranged o the protein. A few of these amino acids on the surface of the molecule fold inwards making what is called the active site. Within the enzyme the active site is where the reactant molecule (in this case the egg white) attaches to the enzyme by random collision. The substrate binds to the active site of the enzyme where the reaction takes place. A reaction is able to takes because the amino acids around the active site hold the substrate in place. This forms an enzyme-substrate complex when the enzyme’s active site binds with the substrate. This is known as the lock and key theory as the substrate attaches to the active site of the enzyme fitting like a key in a lock. Therefore enzymes are very specific as they will only function correctly if the shape of the substrate matches the active site.
After the enzyme substrate – complex is formed the enzyme changes the substrate into a product molecule. These product molecules then break down and the product is released. The enzymes active site is now free and can be re-used by another molecule to take part in another reaction. This will cause the rate of reaction to increase but eventually it level off because all the active sites are filled. ¹


For the experiment egg white and the enzyme Pepsin will be used. Egg white contains the protein albumen. When Egg white is cooked it appears opaque. If the enzyme protease is added to egg white it is broken down and the solution clears.


Hypothesis- As the concentration of the enzyme protease is increased so will the rate of protein breakdown. However after a bit the enzymes will stop working (denature) as all the active sights will be full and so increasing the concentration will have no effect on the reaction rate.
Apparatus & materials- The following will be needed in order to carry out the experiment
• Laboratory coat, disposable gloves and goggles to ensure safety. Goggles will ensure that nothing gets in to the eyes and that they are protected from the enzyme. Laboratory coat and gloves will make sure that clothing and the hands are protected.
• Five different test tubes for the different concentrations of solution. The testubes will be labelled one- six to ensure that there is no mix up between the tubes. A testube rack will be used to place the tubes to ensure that they are not handled and are on a stable surface.
• 2.55mm syringe to measure the enzyme protease solution. A syringe is more appropriate to use than a beaker or measuring cylinder as only small measurements are needed therefore the syringe will make the measurements more accurate and the results valid.
• A 10cm-measuring cylinder to transfer 5cm of protein to the testubes and the different amounts of distilled water.
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