4 3 MEMBRANE STRUCTURE Biology I MEMBRANE FUNCTION

4. 3 MEMBRANE STRUCTURE Biology, I

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

MEMBRANE FUNCTION 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

MEMBRANE STRUCTURE: 1. PHOSPHOLIPIDS ◦ 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)

MEMBRANE STRUCTURE 1. PHOSPHOLIPIDS 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

MEMBRANE STRUCTURE 2. CHOLESTEROL Lipid Hydrophobic Fits in with fatty acid tails of phospholipids Function: Keeps membrane from freezing or falling apart Helps “stabilize” membrane

MEMBRANE STRUCTURE 3. MEMBRANE PROTEINS Membrane proteins structure: Hydrophobic regions & Hydrophilic regions Hydrophobic regions anchor proteins in the membrane

MEMBRANE STRUCTURE 3. MEMBRANE PROTEINS Which color of the protein is hydrophilic? Hydrophobic?

MEMBRANE STRUCTURE 3. MEMBRANE PROTEINS Function: 1. Transport protein: move material into & out of the cell

MEMBRANE STRUCTURE 3. MEMBRANE PROTEINS Functions: 2. Adhesion protein: helps cells stick together in animal tissue

MEMBRANE STRUCTURE 3. MEMBRANE PROTEINS Function: 3. Receptor protein: Bond to particles outside of cell to trigger changes inside of cell

MEMBRANE STRUCTURE 3. MEMBRANE PROTEINS Glycoproteins – proteins with carbohydrate chains attached

Bozeman membrane FLUID MOSAIC MODEL Describes the cell membrane: Phospholipids are always moving like a fluid and membrane proteins make a pattern in the cell membrane