NEET (UG) 2023 — Question 167

Cellulose is a polysaccharide composed of β-D-glucose units linked by β(1→4) glycosidic bonds. The iodine test for starch produces a blue color due to formation of an iodine-starch complex. This complex forms because starch has helical structures that can trap iodine molecules. Cellulose has a linear structure without complex helices. Due to the absence of helical structures, cellulose cannot trap iodine molecules. Therefore, cellulose does not give a blue color with iodine. Option A is incorrect because cellulose is not helical. Option C is incorrect as iodine doesn't break down cellulose. Option D is incorrect because cellulose is a polysaccharide, not a disaccharide.