The student adds Lugol's iodine (small molecule) to the water surrounding bag X (10% sucrose + starch). After 30 min, the inside of the bag turns blue-black, but the surrounding water remains amber.
Which conclusion is best supported?
- A
Water did not move during the experiment
- B
Starch diffuses out of the bag
- Ccheck_circle
The membrane is permeable to iodine but not to starch
- D
Iodine and starch are both impermeable
Explanation
Iodine (small) crossed into the bag and produced the starch-iodine color change inside. Starch is too large to cross, so the surrounding water remained amber. Membrane permeability depends on molecular size.