Iodine and plant cells

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leongw
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Iodine and plant cells

Post by leongw » Wed Mar 21, 2007 2:46 pm

Why does blue spot appears when iodine come into contact with plant cells?

Jammerz
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Post by Jammerz » Thu Mar 22, 2007 4:23 am

Plant cells can contain stored starch grains. Starch turns blue when it comes in contact with iodine (which is why Lugol's iodine for example can be used as an indicator for starch).

muraceae
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Post by muraceae » Thu Mar 22, 2007 5:48 pm

"The iodine (in the form of I5- 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."
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