The document discusses different transport processes across cell membranes. It explains that diffusion is the passive movement of particles from areas of high concentration to low concentration without needing energy. Osmosis, the diffusion of water through the selectively permeable cell membrane, occurs to maintain water balance in cells. Particles can enter and leave cells through membrane proteins via passive transport through diffusion or active transport using cellular energy. Larger particles move in and out of cells through endocytosis, which surrounds particles with the membrane, and exocytosis, which releases particles using vesicles.