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CAL Biology
Practical 2 – Identification of Biochemicals in Pure Form
Name :…………………………………………………………….
MARK:
Class :…………………………………………………………….
PRACTICAL 2: IDENTIFICATION OF BIOCHEMICALS IN PURE FORM
CAUTION:
Any heating that has to be done in the following tests should be carried out in a water bath at the boiling point of water. Direct heating of test-tubes should not take place.
Introduction
Biochemical Tests
Qualitative
- present/ absent
Semi-quantitative
- present in >/< amount
- a rough estimation
Quantitative
- precise numerical value of the quantity
Aims: 1) To learn how to carry out biochemical tests to identify biochemicals in pure form.
2) To learn the basis of biochemical tests.
3) To find out the concentration of ascorbic acid in a vitamin C solution.
4) To classify biochemical tests into qualitative, semi-quantitative & quantitative tests.
5) To learn how to use the correct significant figures for numbers calculated from experimental results.
6) To learn the meaning of some scientific terms used in experiments.
Materials: (as projected on screen)
Method/ Procedure:
I.
CARBOHYDRATES: REDUCING SUGARS
The reducing sugars include all monosaccharides, such as glucose and fructose, and some disaccharides, such as maltose.
Test
Benedict’s test
Add 2cm3 of a solution of the reducing sugar to a test-tube. Add an equal volume of Benedict’s solution. Shake and place into boiling water. Boil for
2-5 minutes; shake continuously to minimise spitting.
Note: Make sure you standardise the boiling time for all specimen.
Observation
Basis of test
The initial blue colouration of the mixture turns green, then yellowish and may finally form a brick-red precipitate. Benedict’s solution contains copper sulphate. Reducing sugars reduce soluble blue copper sulphate, containing Cu2+ to insoluble red-brown copper oxide, containing Cu+. The latter is seen as a precipitate.
Note:
1) Read the colour
Practical 2 – Identification of Biochemicals in Pure Form
Name :…………………………………………………………….
MARK:
Class :…………………………………………………………….
PRACTICAL 2: IDENTIFICATION OF BIOCHEMICALS IN PURE FORM
CAUTION:
Any heating that has to be done in the following tests should be carried out in a water bath at the boiling point of water. Direct heating of test-tubes should not take place.
Introduction
Biochemical Tests
Qualitative
- present/ absent
Semi-quantitative
- present in >/< amount
- a rough estimation
Quantitative
- precise numerical value of the quantity
Aims: 1) To learn how to carry out biochemical tests to identify biochemicals in pure form.
2) To learn the basis of biochemical tests.
3) To find out the concentration of ascorbic acid in a vitamin C solution.
4) To classify biochemical tests into qualitative, semi-quantitative & quantitative tests.
5) To learn how to use the correct significant figures for numbers calculated from experimental results.
6) To learn the meaning of some scientific terms used in experiments.
Materials: (as projected on screen)
Method/ Procedure:
I.
CARBOHYDRATES: REDUCING SUGARS
The reducing sugars include all monosaccharides, such as glucose and fructose, and some disaccharides, such as maltose.
Test
Benedict’s test
Add 2cm3 of a solution of the reducing sugar to a test-tube. Add an equal volume of Benedict’s solution. Shake and place into boiling water. Boil for
2-5 minutes; shake continuously to minimise spitting.
Note: Make sure you standardise the boiling time for all specimen.
Observation
Basis of test
The initial blue colouration of the mixture turns green, then yellowish and may finally form a brick-red precipitate. Benedict’s solution contains copper sulphate. Reducing sugars reduce soluble blue copper sulphate, containing Cu2+ to insoluble red-brown copper oxide, containing Cu+. The latter is seen as a precipitate.
Note:
1) Read the colour