Find out the effect of temperature on enzyme activity.

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Title: Temperature on Enzyme activity.

Date: 29 September 2004

Aim: To find out the effect of temperature on enzyme activity.

Theory:

Like all enzymes, amylase catalyses a (bio) chemical reaction. A fundamental of chemical thermodynamics is that all reaction rates will increase as the temperature increases. With a typical amylase, therefore as you increase the temperature to the optimum, the rate at which an enzyme catalyses the breakdown of starch increases.

Effect of temperature on reaction rate

Increasing temperature will increase the rate of chemical reactions generally (kinetic energy of reactants is raised which increases the chances of favorable collisions). Enzyme catalyzed reactions will also increase with temperature due to the same reasons. However, catalytic activity depends on the enzyme having the correct conformation (molecular shape). As temperature increases the conformation of the enzyme is disrupted due to the increased kinetic energy of the enzyme molecule itself.

Materials:

1. test tube rack        2. teat pipette                3. starch solution        

4. 3 glass beakers        5. thermometer        6. 7 test-tubes

7. iodine solution        8. ice                        9. clock

10. marker                11. amylase solution

Procedure:

  1.  Seven test-tubes were labeled, 1,2,3,4,5,6, and 7
  2. 3 cm of starch solution was placed in to each of test-tube 1, 2 and 3.
  3. 4 drops of iodine solution was added to each of these solutions.
  4. 1 cm of amylase solution was placed in test-tubes 4, 5, and 6
  5. 3 beakers were labeled A, B and C.
  6. Beaker A’s temperature was about 10oC using ice to water. Beaker B’s temperature was 20oC using cold water and beaker C’s temperature was about 35oC by heating.
  7. Test tubes 1 and 4 were placed in beaker A, test tubes 2 and 5 were placed in beaker B and test tubes 3 and 6 were placed in beaker C.
  8. They were left for five minutes after the amylase from 4 was placed in test tube 1, the amylase from 5 was placed in test tube 2 and the amylase from 6 was placed in test tube 3. Each test tube was shaken to mix its contents and test-tubes 1, 2 and 3 were returned to their respective water baths and observed
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Observation:

Discussion:

Firstly iodine forms a complex with the starch solution to give the characteristic blue-black color. Starch consists of two types of molecules, amylose (normally 20-30%) and amylopectin (normally 70-80%). The unbranched amylose is a chain of glucose molecules bounded together. The chain is coiled in the shape of a helix.

Fig 1 Starch-iodine complex

 The iodine inserts itself into the helix making it rigid. This changes the color to blue. When heat is applied, the complex is destroyed and the solution becomes ...

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