TRANSPORT IN CELLS

• diffusion is the movement of particles from an area of high concentration to an area of lower concentration, down a concentration gradient.
• diffusion happens in both solutions and gases because particles are free to move around
• • The bigger the concentration gradient (the difference in concentration) the faster the diffusion rate.
  • a higher temperature increases the diffusion rate - particles have more energy so they move faster
• dissolved substances can move in and out of the cell by diffusion
• only very small molecules can diffuse through the cell membrane:

  • oxygen (needed for respiration)
  • glucose
  • amino acids
  • water
• big molecules like starch and proteins cant fit through the cell membrane
• the larger the surface area of the membrane, the faster the rate of diffusion