Osmosis Flashcards
What is a partially permeable membrane
A membrane with very small holes in it. A cell membrane is a partially permeable membrane
Why do water molecules pass both ways through the membrane during osmosis.
The water molecules move about randomly during osmosis but there are more water molecules on one side than the other; there’s a steady net flow of water into the region with fewer water molecules
What does the study net flow of water mean
The solution with less water gets more dilute because water diffuses into it
How does water move into and out of cells
By osmosis. The tissue fluid surrounds cells - it is water with oxygen, and glucose dissolved in it. It’s squeezed out of the blood capillaries to supply the cells with everything they need. The tissue fluid will have a different concentration to the fluid inside the cell, and so water will either move into the cell from the tissue fluid or out of the cell by osmosis
What happens if a cell is short of water
The solution inside will become quite concentrated. This usually means the solution outside is more dilute and so water will move into the cell by osmosis
What happens if a cell has lots of water
The solution inside will be more dilute and water will be drawn out of the cell and into the fluid by osmosis
When are cells said to be turgid
When a plant is well watered all of its cells will draw water in by osmosis and become plump and swollen.
What is turgor pressure
When the contents of the cell push against the cell wall. Turgor pressure helps to support the plant tissues
Why do plants start to droop if there is now water in the soil
The cells start to lose water and so lose their turgor pressure. The cells are then said to be flaccid
What does the inelastic cell wall do
Keep the cells shape when it is flaccid
What is osmosis
The net movement of water molecules across a partially permeable membrane from a region of high water concentration to lower water concentration
