Biology, I

 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 and nutrients to into the cell and wastes to exit the cell

◦ Lipid with…  2 fatty acids  1 glycerol  1 phosphate group  1 polar group ◦ Fatty acids (tails) are hydrophobic (water-fearing) ◦ The rest of the phospholipid (head) is hydrophilic (water-loving)

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  Hydrophobic regions anchor proteins in the membrane

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

 Function: 1. Transport protein: move material into & out of the cell

 Functions: 2. Adhesion protein: helps cells stick together in animal tissue

 Function: 3. Receptor protein: Bond to particles outside of cell to trigger changes inside of cell

 Glycoproteins – proteins with carbohydrate chains attached

 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