Biology Unit 3 - Gas and Solute Exchange

Gas and Solute Transport

Substances move by diffusion, osmosis and active transport.

Life processes require gases or other dissolved substances believe they can happen.For photosynthesis to happen carbon dioxide and water have to get into the plant cells. For respiration to take place, glucose and oxygen have to be inside the cells. Waste substances also need to move out of cells so that the organism can dispose of them.

These substances move to where they need to be via diffusion, osmosis and active transport.

• Diffusion, is where particles move from an area of high concentration to an area of low concentration. For example gases can just diffuse through one another, like a smell spreading through a room. Alternatively, dissolved particles can diffuse in and out of cells. (All things except water molecules).
• Osmosis; the net movement of water molecules from an area of high concentration (dilute) across a semi-permeable membrane to an area of low concentration (more concentrated).
• Osmosis and diffusion involve travelling down a concentration gradient, however sometimes substances need to move in the opposite direction. From an area of low concentration to an area of high concentration. This is called active…