Year 12s: what will be the first way you research your future options? >>

Biology IGCSE Past Paper Question-how to answer?

The question is in the attachment below - the answer is supposed to be option C but can you explain why?

Screen Shot 2016-01-09 at 10.16.49 pm.png65.9KB

Hi

I think the question is talking about osmosis. Which is when the water moves down a concentration gradient from a high concentration to a low concentration through a semi permeable membrane. There is lots of water around the potato and very little water in the concentrated glucose solution, so the water molecules in the potato cells around the glucose solution move into the concentrated solution so it becomes less concentrated. Those potato cells now have less water in, so for osmosis to balance out the potato cells they draw water from the cells next to them and this continues until you reach the water which is pulled into the potato cells to overall reduce the concentration of the glucose solution and reach a balance. That is why we see the water go down because it has travelled through the potato to dilute the concentrated glucose solution so there is a balance of water molecules.

I hope this helps

James