List and describe the four factors that affect the rate of diffusion
1. Concentration difference: substances move from place with high concentration to a place with low concentration across the membrane. If the gradient of concentration is zero, there will be no diffusion. 2. Temperature: Increasing of temperature increases the rate of diffusion because molecules get additional energy for moving. Decreasing of temperature decreases the rate of diffusion by decreasing the energy of particles. 3. Diffusion distance: the rate of diffusion will befaster when the distance is small; the rate of diffusion will be more slowly when the distance is long. 4. Molecular weight of the diffused particles: small particles move faster than heavy particles. Small particles can move through the membrane by dissolving into phospholipids.