Work out the results expected of standard tests used by scientists to identify the presence of specific chemicals which may be found in cells.

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CHEMICAL TESTS FOR CELLULAR MOLECULES.

Experiment Number 1                                                                                             03-02-04

Partners: Philippa Pretorius and Claire Walter                                        Suzanne Poulgrain

AIM:

To work out the results expected of standard tests used by scientists to identify the presence of specific chemicals which may be found in cells.

A.        TEST FOR PROTEIN

PROCEDURE:

  1. 3mL of egg white solution was placed in a test tube.
  2. 1mL each of dilute sodium hydroxide solution and dilute copper sulfate solution was added.
  3. The resulting liquid was observed and described in Table 1.
  4. Steps 1, 2 and 3 were repeated using water in place of egg white solution.
  5. Steps 1, 2 and 3 were repeated using bread, meat and biscuit. All ingredients were tested separately.  

RESULTS: _                        Table 1 – Results of Protein Testing

DISCUSSION / CONCLUSIONS:

Protein is an important cell chemical and is constantly needed by the body.  As a result of this it is found in many common food stuffs.  In this test, water was used as a control and shows the results when no protein is present.  When water, bread and biscuit were tested there was no change in the colour of the solution.  This indicates that there is a minimal amount of protein within these substances.  The results of this investigation show that both egg white solution and meat react similarly to this test.  Since it is known that egg white solution contains protein it can therefore be concluded that meat does likewise.  In conclusion this test has identified protein within some common materials.  

B. TEST FOR STARCH

PROCEDURE:

1.        A small amount of starch was placed on a spotting tile.

  1. 2-3 drops of Lugol’s iodine solution was added to the starch.
  2. The resulting substance was observed and described in Table 2.
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3.        Steps 1, 2 and 3 were repeated using water in place of starch.

5.        Steps 1, 2 and 3 were repeated using  ground: potato, biscuit and meat. All ingredients were tested separately.

RESULTS:                         Table 2 – Results of Starch Testing

DISCUSSION / CONCLUSIONS:

Starch is needed by the plants as an energy supply.  It is used in place of other forms of carbohydrates as it is insoluble.  In this test water is used as a control and shows the results of the test when no starch is present.  When water and meat were used there was no change in the colour ...

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