How does a change in temperature effect the activity of the catalase enzyme on a piece of liver?

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BIOLOGY COURSEWORK INVESTIGATION

How does a change in temperature effect the activity of the catalase

enzyme on a piece of liver?

PLANNING

Background knowledge

An enzyme is a biological catalyst; it alters the rate of reaction without being changed itself. Enzymes are proteins; they have a very precise three- dimensional shape, which forms a one specific active site on the enzyme. Each enzyme can only convert one kind of substrate molecule into one kind of product molecule.

What affects Enzymes?

  • Temperature – Enzymes start to denature if the temperature rises above 37.5 C Increasing the temperature alters the three – dimensional shape of the enzyme therefore the enzyme can no longer fit the substrate
  • pH – Enzymes work best in neutral conditions neither acidic or alkaline.

What effect does catalase have?

Catalase is a very fast reacting enzyme, it is found in many living cells, it breaks down hydrogen peroxide to water and produces oxygen. In fact one molecule of it can deal with six million molecules of hydrogen peroxide in 1 minute. Hydrogen peroxide is toxic so it needs to be changed into harmless substances.

The equation for the reation:

        2H202           Catalase            2H20 + 02  

Reference to praticals referring to enzymes

  • Biology for You Pg. 30 – Experiment 3.1

From looking at this I found that the catalase reacts with the hydrogen peroxide to give out water and oxygen. Oxygen bubbles produce froth on the surface of the solution. In my forthcoming experiment I will expect to see froth being produced.

In my pilot I will need to find a way to get rid of most of the froth.

  • Biology – Nelson Science Pg. 25

After looking at this I learnt that the effect of the temperature does in fact change the rate of the reaction. When the reaction reaches (37 - 40 C), the enzyme denatures and the rate of the reaction decreases. The rate falls rapidly suggesting the enzyme is denaturing.

Taking this information into account I expect the enzyme catalase to show a similar pattern in respect to the temperature.

Information obtained from secondary sources into ‘lock and key’ theory  

  • Encarta 99 – Structure and function of an Enzyme.

Enzymes are large proteins that speed up chemical reactions. In their globular structure, one or more polypeptide chains twist and fold, bringing together a small number of amino acids to form the active site, or the location on the enzyme where the substrate binds and the reaction takes place. Enzyme and substrate fail to bind if their shapes do not fit exactly. This ensures that the enzyme does not participate in the wrong reaction. The enzyme itself is unaffected by the reaction. When the products have been released, the enzyme is ready to bind with a new substrate.

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Pilot Test

After taking the information above into account, I expect to see froth to appear of the surface of the solution if I use pure hydrogen peroxide. But I only want to measure the amount of oxygen given off. In order for me to measure the oxygen only I will need to dilute the hydrogen peroxide. As a result of this I should only see a very same amount of froth appearing on the surface. To measure the amount of froth given off I ...

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