How does a cell regulate osmosis and diffusion?

A cell regulates osmosis and diffusion through several different ways. One way is through the semipermeable membrane, which allows selective movement of molecules, letting water pass through while blocking other substances. Additionally, the structure of cell membranes (phospholipid bilayer) regulates the movement of water-soluble molecules and ions, preventing their free movement. Channel and carrier proteins also help regulate osmosis and diffusion. Channel proteins create channels that allow specific ions or water molecules to pass through, aiding diffusion. Carrier proteins bind to specific molecules, change shape, and transport them across the membrane; this is done either by facilitated diffusion or active transport. Another way is through osmoregulation, which  controls the movement of solutes to manage osmotic pressure and prevent the cell from bursting. Contractile vacuoles are also used to remove excess water in single-celled organisms. Diffusion and osmosis are also regulated by endocytosis and exocytosis. Endocytosis involves the cell membrane taking in large particles or liquids to bring them into the cell using vesicles. Exocytosis involves the release of substances from the cell by vesicles fusing with the membrane. Another way is through aquaporins, which enable rapid movement of water across the cell membrane and allow cells to quickly adjust to changes in osmotic pressure.