Diffusion

• Diffusion is spreading out of particles from a high concentration to a low concentration.
• Diffusion happens in both solutions and gases- that's because the particles in these substances are free to move randomly.
• The bigger the concentration gradient the faster the diffusion rate.
• The simplest type of diffusion is when different gases diffuse through each other. This is what's happening when the smell of perfume diffuses through a room.
• 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 also let things in and out.
• Dissolved substances can move in and out of cells by diffusion.
• Only very small molecules can diffuse through cell membranes.
• Oxygen, glucose, amino acids and water are all diffused through cells.
• Big molecules like starch and proteins can't fit through the membrane.
• The particles move randomly so they go both ways, but if there is a high concentration gradient there is a net movement to the lower concentration side.
• The larger the surface area of the membrane, the faster the diffusion rate because more particles can pass through at once.