Diffusion

• Diffusion is really important in living organisms - it's how a lot of substances get in and out of cells
• Diffusion is the spreading out of particles from a high concentration to a low concentration
• The bigger the concentration gradient, the faster the diffusion rate. A higher temperature will also give a faster diffusion rate because the particles have more energy, so move around faster.
• Cell membranes hold the cell together but they let stuff in and out aswell
• Dissolved substances can move in and out of cells by diffusion
• Only very small molecules can diffuse through cell membranes though things like oxygen, glucose, amino acids, and water
• Big molecules like starch and proteins can't fit through the cell membrane
• Just like with diffusion in air, particles flow through the cell membrane from where there's a higher concentration to where there's a lower concentration
• The particles are only moving about randomly of course, so they go both ways - but if there are a lot more particles on one side of the membrane, there's a net movement from that side