The Plasma (Cell) Membrane

Plasma Membrane Maintaining Balance Separates living cell from nonliving environment Allows flow of nutrients into and out of cell Homeostasis ▫Maintain a stable internal environment Selective permeability ▫Allows some molecules into the cell while keeping others out

Structure of Phospholipid Bilayer Two layers of phospholipids back to back Lipid with a phosphate group attached

Phospholipid Head is polar – interact with aqueous external environment ▫loves water = hydrophilic Tails are non-polar – avoids water ▫afraid of water = hydrophobic Water-soluble molecules will not pass through easily

Phospholipid Bilayer polar hydrophilic Heads nonpolar hydrophobic tails polar hydrophilic Heads

Fluid Mosaic Model Model of the plasma membrane ▫Fluid due to flexible nature of membrane ▫Phospholipids move like water current ▫Proteins in membrane create pattern (mosaic) on membrane surface It’s like a fluid… It’s like a mosaic… It’s the Fluid Mosaic Model!

FluidMosaic

Other Components Cholesterol ▫Helps stabilize phospholipids ▫Stops fatty acid chains from sticking together Proteins on membrane surface aid in cell identification Transport Proteins ▫Span the width of the membrane ▫Regulates which molecules may pass through the membrane

Functions Outside Plasma Membrane Inside Cell Transporter Enzyme Activity Receptor Identity Marker Cell AdhesionAttach to Cytoskeleton

Functions Transporter ▫Exocytosis- moving molecules out of the cell ▫Endocytosis- moving molecules into the cell Enzyme Activity ▫Aid in enzyme activity Receptor ▫Receiving chemical signals Identity Marker ▫Surface protein markers are embedded and aid in cell to cell communication Attach to Cytoskeleton ▫ Maintains structure and shape ▫ Attached to fibers that are on cytoskeleton Cell Adhesion ▫ Allows cells to come together and adhere Cell Adhesion ▫ Allows cells to come together and adhere