Define the iodine test - carbohydrates, Biology

Define the Iodine Test - Carbohydrates?

This test is given by polysaccharides and is not given by monosaccharides or disaccharides.

Principle

Iodine forms a coloured adsorption complex with polysaccharides. When starch is mixed with iodine, an intensely colored starch/iodine complex is formed. The minute details of the reaction are still not clear.

   Test

Reagents Required

      Methodology    

Observation

Iodine Test

- Solutions of glucose, fructose, galactose, lactose, maltose, sucroseand polysac- charide.

- Iodine solution in potassium iodide

For mono and disaccharides: To 5 ml of glucose solution taken in a 10 ml test tube, add 3-4 drops of iodine solution. Observe the change in colour. Repeat the test with fructose, galactose, lactose, maltose, and sucrose.

For polysaccharides: To about 5 ml of polysacch-aride solution add drop by drop a dilute solution of iodine in potassium iodide. See the change in colour. (in Performing this test the solution must always be neutral or acid in reaction).

Divide the coloured solution into three parts:

(i) Heat one part and cool it.

(ii) To the second part add alcohol.

(iii) To the third part add NaOH solution.

No change in the colour of the sugar solution containing monosaccharide on addition of iodine.

Disaccharides do not form adsorption complex with iodine solution.

The polyasaccharide molecules form adsorption complexes with iodine. The composition of the coloured complex is however, not well defined.

Polysaccharides are large colloidal molecules which form aggregated particles called micelles

These micelles combine with iodine to form coloured adsorption complexes.

The starch-iodine or dextrin- iodine adsorption complex dissociates on heating and is reformed on cooling. It is also broken up by alcohol and NaOH.

 

 

 

Posted Date: 6/17/2013 3:15:56 AM | Location : United States







Related Discussions:- Define the iodine test - carbohydrates, Assignment Help, Ask Question on Define the iodine test - carbohydrates, Get Answer, Expert's Help, Define the iodine test - carbohydrates Discussions

Write discussion on Define the iodine test - carbohydrates
Your posts are moderated
Related Questions
Sound is a main mean of communication and entertainment and is also very effective alarm system for some animal. A loud and unwanted or unpleasant sound causes discomfort and is ca


Q How does the amoeboid movement occur and what are examples of beings and cells that use such movements for locomotion? Amoeboid movements are created by cytoplasmic movements

Water Reuse And Recycling Are Becoming   Much More Common As Demands For Water Exceed Supply. Unplanned reuse occurs as the result of waste effluents entering receiving waters or g

Define the term - Functional magnetic resonance imaging Functional magnetic resonance imaging (fMRI) is a recent development that permits simultaneous measurements of the brain

Define Food availability and Food Access? Food availability: This refers to availability of necessary types of food in sufficient quantity, to the individual. The sources may b

Define Class – Arachnida? The class Arachnida (Arachnida = spider) has terrestrial and few aquatic animals. It includes spider, scorpions and mites. 1. Prosoma bears. six pair

What is the main difference between a bird heart and a mammalian heart? The bird heart has a one aortic arch on the right side of its body while the mammalian heart has one on

Explain the Jejuno ileal Bypass and Jaw Wiring? Jejuno-ileal Bypass: Absorptive surface of the small intestines can also be reduced through surgery called the jejuno-ileal by p

What are the main characteristics of the bryophytes? Bryophytes are nonvascular plants, i.e., they do not have conductive tissues and they perform transport of water and nutrie