Cell Boundaries The Cell Membrane The Cell Membrane Thin, flexible barrier Regulates what enters and leaves Protects and supports aka: Phospholipid Bilayer. Consists of: hydrophilic head (water liking) and a hydrophobic tail. (water avoiding) Phospholipid Bilayer: Fluid Mosaic Model Also has Proteins – doorways Carbohydrates – name tags Cholesterol – keeps membrane flexible Therefore referred to as a “fluid mosaic” of different molecules. Cell Boundaries The Function of the Plasma Membrane The Cell Membrane Cells want nutrients Cells get rid of wastes Two ways: Passive Transport – No Cell Energy (ATP) needed Active Transport – Cell Energy (ATP) required Passive Transport - Diffusion Passive Transport – Facilitated Diffusion Passive Transport - Osmosis The diffusion of water molecules through a cell membrane. Concentration gradient depends on amount of dissolved particles (like salt) inside and outside the cell. Isotonic Solution Concentration of a dissolved substance (solute) is the same inside and outside the cell. Isotonic = Dynamic equilibrium. Cell stays same size. Isotonic Solution Hypotonic Solution Concentration of the solute is low outside the cell and higher inside the cell. Water moves INTO the cell. Cell gets BIG like the O in hypOtonic Hypotonic Solution Hypertonic Solution Concentration of the solute is higher outside the cell and lower inside the cell. Water Exits the cell. E Think of the “E” in hyp rtonic Cell shrinks. Hypertonic Solution Assignment Draw and Label Figure 23, 24 and 25 on page 204-205. Complete the Osmosis worksheet.