Testing for Biochemicals

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TITLE: Aspects of Biochemistry

AIM: To determine which biochemicals are present in five (5) unknown solutions

APPARATUS:
• Beakers
• Test tubes
• Test tube holder
• Test tube rack
• Bunsen burner
• Tripod/Clamp stand
• Wire gauze
• Matches
• Red litmus paper

MATERIALS:
• Distilled water
• Benedict’s solution
• Hydrochloric acid
• Sodium hydroxide
• Iodine solution
• Ethanol
• Copper sulphate solution
• Solutions A-E

METHOD:
• Written in past tense
• Written in paragraph form
• See instructions below to help you carry out the tests

TEST FOR REDUCING SUGAR (Benedict’s Test)

1. Add 2 cm3 of the solution to be tested into a test tube. 2. Add 2 cm3 of the Benedict’s solution.
3. Boil in a water bathe for 2 minutes.

Results: Green colour: A trace of reducing sugar
Yellow/Orange colour: A large amount of reducing sugar

TEST FOR NON-REDUCING SUGAR

A complex sugar breaks down into a simple sugar when it is heated with a dilute acid. If Benedict’s test is negative, test for the presence of a non-reducing sugar.

1. Add 2 cm3 of the solution to be tested into a test tube. 2. Add 3 drops of dilute Hydrochloric Acid, HCL
3. Boil in a water bath for 2 minutes.
4. Cool the test tube by placing it in a beaker with tap water. 5. Make the solution alkaline by adding drops of Sodium Hydroxide, NaOH. (Test with litmus paper) 6. Do Benedict’s test.

TEST FOR PROTEIN (Biuret Test)

1. Add 2 cm3 of the solution to be tested in a test tube. 2. Add 2 cm3 of Sodium Hydroxide, NaOH, solution. Mix by shaking the test tube. 3. Add 4 drops of Copper Sulphate, CuSO4.

Positive result: Lavender/Purple...
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