NURSING EXAM QUESTIONS
BIOCHEMISTRY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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glycogen
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starch
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cellulose
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amylose
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Detailed explanation-1: -Starch forms helical secondary structures which can hold iodine, but cellulose does not contain helices, and so cannot hold iodine.
Detailed explanation-2: -(iv)Cellulose gives no colour with iodine solution.
Detailed explanation-3: -Amylose is helical in structure and can hold I2 molecules whereas cellulose, being linear, cannot hold I2. Hence, the iodine test can not be used to detect cellulose in a solution.
Detailed explanation-4: -A positive result for the iodine test (starch is present) was a colour change ranging from violet to black; a negative result (no starch) was the yellow colour of the iodine solution.
Detailed explanation-5: -This is because cellulose cannot hold iodine. Since there are no complex helices in cellulose, it can’t coil around iodine.