Osmosis Lab Essay

4945 Words20 Pages
Investigation 5 Investigating the Effect of Time on the Plasmolysis of Potatoes Research Question What causes potatoes to go soft after being stored for a long time? Aim The aim of this experiment is to investigate how time affects the amount of water · lost by potatoes, by measuring at how much water a cylinder cut from a potato (4cm in length) can take up after various amounts of time, measured in weeks. I will do this by calculating the change of mass of the cylinder, after placing it in water for 1.5 hours, as I predict the amount of water absorbed by the potato cylinder through osmosis, will be the same as the amount of water lost over time Background Information Osmosis is the passive transport of water through a partially permeable membrane of a cell. As this transport is passive and not active, no ATP is needed as the water movement occurs along the concentration gradient through the partially permeable membrane. In plant cells, such as potato cells, when water leaves the cell tissue through osmosis, the cytoplasm and plasma membrane are pulled away from the cell wall. The cell wall however, as it is a semi-rigid structure composed mainly of cellulose, maintains its shape. This loss of water and pulling together of the plasma membrane is called plasmolysis. As observable in flowers when they wilt in the absence of enough water, plant cells rely on turgor pressure, water filling up the cytoplasm, for support. This also explains why potatoes get soft over a longer period of time. When exposed an hypertonic environment, meaning the cells contain a higher concentration of water than there is externally, water will gradually move out of the cells by osmosis. Therefore, when potatoes are left for a longer period of time, the water will be drawn out of the cells, through the partially permeable membrane, causing the cells to become flaccid and eventually
Open Document