Osmosis, Gas and Solute Exchange Flashcards
What is osmosis?
The movement of water molecules across a partially permeable membrane from a region of high water concentration to region of low water concentration.
What is a partially permeable membrane?
One with lots of little holes in it.
Why do water molecules pass both ways?
They move randomly.
What causes a net flow?
More molecules on one side than on the other.
What is tissue fluid?
Fluid that surrounds cells in the body.
What does tissue fluid contain?
Water, with oxygen, glucose and other substances dissolved in it.
Why is it important that the tissue fluid has a different concentration to the fluid inside a cell?
So that water can move into or out of the cell by osmosis.
What do life processes need before they can happen?
Gases or other dissolved substances.
What needs to move out of cells?
Waste substances.
How are substances moved?
Diffusion, osmosis and active transport.
What do gases and dissolved substances have to move through?
An exchange surface.
How are exchange surfaces adapted to maximise effectiveness?
- Thin - short distance to diffuse
- Larger surface area
- Lots of blood vessels
- Gas exchange surfaces are ventilated
Where is the exchange surface in a leaf?
Underneath the leaf.
How does carbon dioxide enter leaves?
Diffusion through stomata.
What diffuses out of leaf stomata?
Oxygen and water vapour.
