Which of the following carbohydrates gives a dark blue colour with iodine?
Correct answer: B. Starch
- A. Amylopectin
- B. Starch
- C. Cellulose
- D. None of these
Explanation
The correct answer is Starch. Starch is composed of two types of glucose polymers: amylose and amylopectin. The iodine test for starch is based on the interaction between iodine and the helical structure of amylose, resulting in a dark blue color. Amylopectin, despite being part of starch, does not produce this color change on its own due to its highly branched structure. Cellulose does not form a complex with iodine because its linear chains do not create the necessary helical structure. Therefore, the statement 'None of these' is incorrect as starch does indeed produce a dark blue color with iodine.
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