4I. Cell Membrane A. General 1. Flexible and allows a unicellular organism to move
5Maintain a high concentration of materials in the cell. The Plasma Membrane4/6/2017B. FunctionMaintain a high concentration of materialsin the cell.2. Keep harmful materials out.3. Control the movement of materials intoand out of the cell.4. Let the cell sense its environment.G. Podgorski, Biol. 1010
65. Protective barrier6. Regulate transport in & out of cell (selectively permeable)7. Allow cell recognition8. Provide anchoring sites for filaments ofcytoskeleton
7Membrane Components The Plasma Membrane 4/6/2017 G. Podgorski, Biol. 1010
8Proteins Are Critical to Membrane Function The Plasma Membrane4/6/2017Proteins Are Critical to Membrane FunctionG. Podgorski, Biol. 1010
99. Provide a binding site for enzymes 10. Interlocking surfaces bind cells together11. Contains the cytoplasm (fluid in cell)
10C. Maintains homeostasis Balanced internal condition of cells.Also called equilibriumMaintained by plasma membrane controlling what enters & leaves the cell.
11ReviewExplain what would happen to a cell if the cellmembrane did not do its job properly.
17Figure 04.3aTitle:Diffusion through the plasma membraneCaption:Simple diffusion through the phospholipid bilayer: Gases such as oxygen and carbon dioxide and lipid-soluble molecules can diffuse directly through the phospholipids.
18Figure 04.1Title:The plasma membrane is a fluid mosaicCaption:The plasma membrane is a bilayer of phospholipids in which various proteins are embedded. Many proteins have carbohydrates attached to them, forming glycoproteins. The wide variety of membrane proteins fall mostly into three categories: transport proteins, receptor proteins, and recognition proteins.
19The Plasma MembraneThe Plasma MembraneFLUID MOSAIC MODEL*1. FLUID- because individual phospholipids and proteins can move around freely within the layer, like it’s a liquid.2. MOSAIC- because of the pattern produced by the scattered protein molecules when the membrane is viewed from above.G. Podgorski, Biol. 1010G. Podgorski, Biol. 1010*
20Cell MembranePolar heads are hydrophilic “water loving”Nonpolar tails are hydrophobic “water fearing”Makes membrane “Selective” in what crosses
21The Plasma Membrane G. Podgorski, Biol. 1010 The Plasma Membrane *
22Cell Membrane Hydrophobic molecules pass easily; hydrophillic DO NOT The cell membrane is made of 2 layers of phospholipids called the lipid bilayer
23SolubilityMaterials that are soluble in lipids can pass through the cell membrane easily
24Semipermeable Membrane Small molecules and larger hydrophobic molecules move through easily.e.g. O2, CO2, H2O*
25Semipermeable Membrane Ions, hydrophilic molecules larger than water, and large molecules such as proteins do not move through the membrane on their own.*