Diffusion - Osmosis Flashcards
What is diffusion?
The gradual movement of particles from an area of higher concentration to an area of low concentration.
What substances does diffusion happen in and why?
Liquids and gases because the particles in these substances are free to move about randomly.
What three things speed up diffusion and how?
- Concentration difference: The bigger the concentration difference, the faster diffusion happens.
- Distance: Substances diffuse much quicker when they do not have as far to move.
- Surface area: The more surface area available, the faster they can get from one side to another.
What can move in and out of cells?
Substances
What type of molecules can diffuse through the cell membrane? Give examples
Only very small molecules such as glucose, amino acids, water and oxygen
Where does gas exchange happen?
In the little air sacs called alevoli, located in the lungs
What is osmosis?
The movement of water molecules across a partially permeable membrane, from a region of higher concentration to a region of lower water concentration.
Define a ‘partially permeable membrane’
A membrane with very small holes in it- only tiny molecules such as water can pass through them.
What is tissue fluid made up of?
It is water with oxygen, glucose and other stuff dissolved in it.
What does tissue fluid do?
It is squeezed out of the blood capillaries to supply the cells with everything they need.
What does it mean if tissue fluid has a different concentration to the fluids inside of the cell?
It means that either water will move into the cell from the tissue fluid, or out of the cell by osmosis.
What does it mean if a cell becomes short of water?
When a cell becomes short of water, the fluid inside of it becomes fairly concentrated. This will usually mean that the solution outside is more dilute, therefore water will move into the cell by osmosis.
What happens if a cell has too much water?
If a cell has lots of water, the solution inside of it will be more dilute, therefore water will be drawn out of the cell and into the fluid outside by osmosis.
