Simple Diffusion Relative to the concentration gradient movement is doWn the concentration gradient ONLY (higher concentration to lower concentration) (outside) lipid- soluble molecules Rate of diffusion depends on O2, CO2, H2O The concentration gradient Charge on the molecule Size Lipid solubility 0888 (inside)Simple Diffusion Relative to the concentration gradient movement is DOWN the concentration gradient ONLY (higher concentration to lower concentration) Rate of diffusion depends on • The concentration gradient • Charge on the molecule • Size • Lipid solubility