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

Procedure

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)

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

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!!

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.

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.

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

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

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.

Discussion

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.

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

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

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

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

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

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.

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.

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

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

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

ANY QUESTIONS?