 Surrounds all cells  Regulates cell’s internal environment  Maintains HOMEOSTASIS Maintains the same conditions constant inside the cell, regardless of external conditions

 Regulates what enters and exits the cells  Selectively permeable Only allows specific materials to pass over the membrane Examples: spaghetti strainer & mosquito netting Allows water & nutrients to enter the cell and wastes to leave the cell

◦ Lipid with…  2 fatty acids  1 glycerol  1 phosphate group  1 polar group ◦ Fatty acids are hydrophobic ◦ The rest of the phospholipid is hydrophilic

Form a bilayer ◦ Cell membrane has two layers of phospholipids ◦ Polar “heads” attracted to water, carbs, proteins outside the cell and in the cytoplasm  Face outward ◦ Non-polar “tails” not attracted to water  Face inward

 Lipid  Hydrophobic Fits in with fatty acid tails of phospholipids  Function:  Keeps membrane from freezing or falling apart  Helps “stabilize” membrane

 Membrane proteins structure:  Hydrophobic regions & Hydrophilic regions  These help membrane proteins STAY in membrane

 Which color of the protein is hydrophilic?  Hydrophobic?

 Function:  Recognize material & transport it into or out of cell

 Describes the cell membrane: cell membrane  Phospholipids are always moving like a fluid and membrane proteins make a pattern in the cell membrane Bozeman membrane