Understanding Cell Membranes and Transport Processes

Cell membranes are sophisticated barriers that regulate the entry and exit of substances in cells. They are selectively permeable, meaning they control what can pass through. Composed of a phospholipid bilayer, which is flexible, cell membranes also contain proteins that function as receptors and transporters. Small molecules like carbon dioxide and oxygen can easily pass through, while larger molecules such as glucose require transporter proteins. Diffusion describes the movement of molecules from areas of high concentration to low concentration, while osmosis refers to the movement of water across a selectively permeable membrane. Cells react differently to varying water concentrations; animal cells may burst or shrink, while plant cells may become turgid or plasmolysed.