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Carbohydrates, especially starch, which is a polysaccharide carbohydrate. Starch turns deep purple when tested with iodine.
Use iodine to test a leaf for starch | Plant Physiology | Biology
yes amylose yields a blue color and amylopectin yields a purple color
Iodine salts haven't starch.
Iodine stains starch contained in cells. Iodine is also used to distinguish between Gram negative and Gram positive bacteria. The Gram stain contains iodine.
Iodine
Starch can give a negative iodine test when starch is mixed with iodine in water. The iodine gets stuck in the coils of beta amylase molecules and the starch forces the iodine atoms into a linear arrangement in the central groove of the coil.
Carbohydrates, especially starch, which is a polysaccharide carbohydrate. Starch turns deep purple when tested with iodine.
Perhaps the iodine solution was old and gave a false negative.
By testing whether adding iodine darkens it.
It is simply called the Starch test which is the process of testing something for the presence of starch. Add Iodine solution to whatever is it you're testing and a dark blue/black color indicates the presence of starch
As you know that iodine act as indicator for testing of starch so when a drop of iodine is added to starch it turns bluish black but when added to distilled water nothing happens except the colour of water which turns brown and its is the colour of iodine.
Use iodine to test a leaf for starch | Plant Physiology | Biology
Iodine is famous for testing of the presence of starch. I would assume starch is present in the solution, therefore iodine would turn blue. Originally, the colour of iodine solution is brown.
When starch is mixed with iodine in water, an intensely colored starch/iodine complex is formed. Many of the details of the reaction are still unknown. But it seems that the iodine (in the form of I 5- ions) gets stuck in the coils of beta amylose molecules (beta amylose is a soluble starch). The starch forces the iodine atoms into a linear arrangement in the central groove of the amylose coil. There is some transfer of charge between the starch and the iodine. That changes the way electrons are confined, and so, changes spacing of the energy levels. The iodine/starch complex has energy level spacings that are just so for absorbing visible light- giving the complex its intense blue color..
The presence of starch can be tested with the help of Iodine. Similarly Benedict's test solution is also used to detect the presence of starch.
Starch has high affinity for Iodine and in presence of iodine crystals starch turns blue from being colourless. This the fundamental that is used for chemically identifying the starch.