A defining feature of biological membranes is their selective permeability, which allows them to control the movement of substances in and out of the cell or compartment. This selective permeability is critical for maintaining distinct internal environments and enabling cellular functions. Biological membranes are primarily composed of a lipid bilayer with embedded proteins, organized as a fluid mosaic that is asymmetric and dynamic.
Key Defining Features of Biological Membranes
- Lipid bilayer structure: Composed mainly of phospholipids, cholesterol, and glycolipids, forming a semi-permeable barrier.
- Selective permeability: The membrane permits controlled passage of molecules based on size, charge, and chemical properties, enabling regulation of the internal cell environment.
- Fluid mosaic model: The lipids and proteins within the membrane are fluid and can move laterally, allowing flexibility and dynamic interaction.
- Asymmetry: The membrane's two leaflets differ in lipid and protein composition, facing distinct environments inside and outside the cell.
Thus, the most defining and fundamentally important feature of biological membranes is their selective permeability.
