Diffusion is the separation of the particles, resulting in a net movement from a region of a higher concentration to a region with a lower concentration. The greater the difference in concentration, the faster the rate of diffusion. (concentration gradient)
What is osmosis?
Osmosis is the diffusion of water from a dilute to a more concentrated solution through a partially permeable membrane.
What is active transport?
the movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring energy.
How can cells be specialised for exchanging materials? (3)
1. Having a large surface area that is thin, to provide a short diffusion path
2. (in animals) having an efficient blood supply
3.(in animals, for gaseous exchange) being ventilated
How is the small intestine and lungs in mammals adapted for exchanging materials?
Large surface area
Alveolar walls are one cell thick....gases diffuse across a small distance