BIOL 1001 Chapter : Chapter 5 Cell Membranes 2
Document Summary
The cell membrane is usually the outermost barrier of the cell. (fig 5-1) The plasma membrane contains the cell but still allows the cell to interact with the environment. The plasma membrane functions: isolate the cell environment, regulate exchange between inside and outside, communicate with other cells, regulate biochemical reactions, create attachments with other cells. Plasma membrane is the membrane at the boundary of every cell that acts as selective barrier thereby regulating the cell"s chemical environment. Phospholipids are molecules which can form membranes naturally (fig 5. 3) hydrogen bonds form between water and the phospholipid heads, tails are located on the inside. Outside is hydrophyllic, inside is hydrophobic: biological membranes contain proteins. As phospholipids isolate cell from the environment, proteins selectively exchange substances and communicate with the environment. Singer and nicolson: fluid-mosaic model each membrane consists of a mosaic of proteins that constantly shift and flow within a fluid formed by a double layer of phospholipids.