1. REACTION OF CARBOHYDRATE
BY: DR. BEENISH ZAKI
INSTRUCTOR DEPARTMENT OF BIOCHEMISTRY

2. Procedure

3. Test Tube rack Test tube holder Test tube (4 in number)
Equipment required
Each student needs:
Test Tube rack
Test tube holder
Test tube (4 in number)

4. MOLISCH’S TEST PROCEDURE Take 2ml of solution in a test tube.
Add two drops of Molish’s reagent.
Mix it well.
Under the cooling conditions incline the test tube and add 2 ml concentrated H2SO4 slowly along the sides of the test tube.
Don’t mix the content

5. H2SO4 is sulphuric acid.
Sulphuric Acid is the most corrosive acid.
This reaction is exo-thermic reaction.
Acid and Water don’t go well together.
Please be CAREFUL!!

6. BENEDICT’S TEST PROCEDURE Take 5ml of Benedict’s reagent
Add 8 drops of solution to it.
Mix well.
Boil it for 2 minutes.
Cool under tap water.

7. Seliwanoff’s Test PROCEDURE Take 3 ml of Seliwanoff’s reagent.
Add 3ml of carbohydrate solution.
Mix well and heat for 3 minutes.
Cool under tap water.

8. IODINE TEST PROCEDURE Take 2ml of solution in a test tube.
Add 2 drops of iodine solution
Mix well

9. Molisch's Test Documentation Principle Observation Inference
As you get your results start writing your observation in the observation column. The principle and inference will be discussed at the end of the session.
Molisch's Test
Principle
Observation
Inference

10. Before You Start Please button up your laboratory coats.
Girls tie your hairs
Check the temperature of the water bath. (>90)
Cool for no more than half a minute under tap water.

11. Discussion

12. Principle Of Molisch’s Test
General test for carbohydrates
Molisch Reagent composition: 5% alcoholic α- napthol.
Carbohydrates in the presence of hot mineral acids undergo dehydration forming hydroxy - methyl furfurals.
This condenses with α-napthol to form a purple ring at the junction of the two layers.

13. Molisch’s test General test for carbohydrates Observation Inference
A purple ring is observed at the junction of the two layers
Indicates the given solution is a carbohydrate solution

14. Content’s of Benedict's reagent
Copper sulfate: provide cupric ions
Sodium Citrate: Prevents the precipitation of cupric ions
Sodium Carbonate: Provides an alkaline medium

15. Principle of benedict’s test
In an alkaline medium carbohydrates form enediols .
Enediols reduce cupric ions to cuprous forming a colored complex.
It is called as semi quantitative test which gives an approximate percentage of sugar present in the urine of a diabetic person

16. BENEDICT’S TEST Observation Inference
Colour of the solution changes from blue to green, yellow, orange
Indicates the presence of a reducing sugar.

17. INTERPRETATION OF BENEDICT’S TEST
Colour
Percentage of sugar
Green
0.5 (+)
Yellow
1.0 (++)
Orange
1.5 (+++)
Red
2.0 (++++)

18. Importance of the Benedict's Test
Used in the preparation of Urostix for diagnosing glucose in urine
Used by Diabetics to check their glucose status.

19. Principle of Seliwanoff's test
Seliwanoff's Reagent composition: Resorcinol in Concentrated HCL
Principle:
In acidic medium carbohydrates form furfurals which react with resorcinol to give a cherry red colour.

20. Seliwanoff's test Observation Inference Cherry red colour is observed
Indicates the presence of a ketohexose i.e fructose.

21. Principle of Iodine test
Principle: Starch a polysaccharide forms a complex with iodine which gives a blue colour.

22. IODINE TEST Observation Inference Light blue colour is observed
Indicates the presence of starch

23. ANY QUESTIONS?