 Many molecules and ions dissolve in the cytoplasm and outside of the cell  The concentration of substances is different inside and outside of the cell  Molecules will diffuse, to equalize, and need to pass through the cell membrane  Selectively permeable
{"Image DocumentName": "Movement of Substances", "Image ImageDescription": "Particles of a substance will move randomly. If there is a concentration gradient (uneven concentration) then diffusion occurs. Diffusion is the movement of a substance from an area of high concentration to low caused by the random movement of particles.", "Image XResolution": "37", "Image YResolution": "37", "Image ResolutionUnit": "Pixels/Centimeter", "Image Software": "SlidePlayer", "Image YCbCrPositioning": "Centered"}