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Download The Plasma Membrane
Transcript
The Plasma Membrane AP Biology Selective Permeability • • • • Brings in certain substances Releases or keeps out certain substances Maintains water balance Essential for life Structure of the membrane • Composed largely of phospholipids • Arranged in a bilayer • The hydrophilic heads face the outside of the membrane • The hydrophobic tails are inside the membrane away from water Phospholipid Bilayer Water bathes the outside of the cell and makes up most of the cytoplasm Fluid Mosaic Model • The membrane has a fluid quality: will ooze if punctured • Parts move and interact • Mosaic means many parts or components Components of the Mosaic • • • • • Phospholipids Glycolipids Sterols Proteins Glycoproteins Types of Proteins • • • • • Transport proteins Receptor proteins Recognition proteins Adhesion proteins Cell to cell communication proteins Transport Proteins • Allows water soluble molecules to move through membrane • Binds substance on one side, and releases it on the other • Glucose, ions, large polar molecules • May be active or passive Receptor Proteins • Bind substances outside the cell which triggers some cellular activity • Hormones • Perfect fit: lock and key Recognition Proteins • Identify each person’s cells as their own • Must be matched in transplants, blood transfusions, etc. Adhesion Proteins • Help cells of the same type stick together in tissues • These are glycoproteins with oligosaccharides attached. Cell to Cell Communication Proteins • Cell to cell communication proteins: match up with another cell to pass on a signal Permeability • Some substances move across easily • These include substances which are soluble in lipids (nonpolar) CO2, O2, and some H2O. • Glucose, amino acids, and other large molecules that do not dissolve in lipids cannot pass through • Most water molecules, and ions such as H+, NA+, K+, and Ca+ cannot pass through • Need transporter proteins Permeability
