Gas and Solute Exchange

Substances move by Diffusion, Osmosis and Active Transport

• Life processes need gases or other dissolved substances to happen

• e.g. For photosynthesis to happen, carbon dioxide and water have to get into plant cells.

• e.g. For respiration to take place, glucose and oxygen both need to get into cells

• Waste substances need to move out of cells so the organism can get rid of them

• These substances move to where they need to be by diffusion, osmosis and active transport:

• Diffusion - where particles move from an area of high concentration to area of low concentration

• e.g. gases can diffuse through one another, like smell spreading through a room

• Alternatively, dissolved particles can diffuse in and out of cells through cell membranes

• Diffusion and osmosis both involve stuff moving from area of high concentration to area of low concentration.

• Sometimes substances need to move in the other direction - active transport

• In life processes, gases and dissolved substances have to move through some sort of exchange surface.

• The exchange surface structures have to allow enough of necessary substances to pass through

• Exchange surfaces and adapted to maximise effectiveness:

• They…