3.1 diffusion

• diffusion - net movement of particles from a region of high concentration to a region of low concentration
• cell membrane restrict the free movement of the molecules
• partially permeable membrane - allows some molecules to pass through easily but others with difficulty or not at all
• diffusion helps living organisms to obtain many of their requirements, to get rid of many of their waste products & to carry out gas exchange for respiration
• energy for diffusion comes from the kinetic energy of random movement of molecules & ions (Brownian motion)
• factors that influence diffusion: surface area, temperature, concentration gradient, distance
• larger surface area = higher rate of diffusion
• higher temperature = higher rate of diffusion
• higher (steeper) concentration gradient = higher rate of diffusion
• on the side with higher concentration = more random collisions against cell membrane occurs
• shorter distance = higher rate of diffusion