Cell Membrane and Transport PDF

Function of the Cell Membrane: separates the components of a cell from its environment provides protection and support regulates the flow of materials into and out of cell—selectively permeable helps cells maintain shape Cell Membrane  Phospholipids...

Function of the Cell Membrane: separates the components of a cell from its environment provides protection and support regulates the flow of materials into and out of cell—selectively permeable helps cells maintain shape Cell Membrane  Phospholipids Polar Hydrophilic head Hydrophobic tail Interacts with water Membrane Lipids Phospholipids Lipid Bilayer Lipid Bilayer is Fluid Cholesterol Cholesterol and unsaturated FA prevent packing of phospholipids  Membrane Proteins 1. Channels or transporters Move molecules in one direction 2. Receptors Recognize certain chemicals  Membrane Proteins 3. Glycoproteins Identify cell type 4. Enzymes Catalyze production of substances Membrane Proteins Protein Properties Membrane Asymmetry Cell fusion experiment proves membrane is fluid Cellular Transport  Types of Cellular Transport Passive Transport Weeee!! ! cell doesn’t use ATP 1. Diffusion high 2. Facilitated Diffusion 3. Osmosis low Active Transport cell does use energy This is gonna 1. Protein Pumps be hard 2. Endocytosis high work!! 3. Exocytosis low Cell Transport PASSIVE TRANSPORT  Passive Transport cell uses no energy in the form of ATP cell only uses KINETIC ENERGY molecules move randomly Molecules spread out from an area of high concentration to an area of low concentration. (HighàLow)  3 Types of Passive Transport 1. Diffusion 2. Facilitative Diffusion – diffusion with the help of transport proteins 3. Osmosis – diffusion of water  Passive Transport: Diffusion 1. Diffusion: random movement of particles from an area of high concentration to an area of low concentration. (High to Low) Diffusion continues until all molecules are evenly spaced (equilibrium is reached) Note: molecules will still move around but stay spread out. Diffusion  Passive Transport: Facilitated Diffusion 2. Facilitated diffusion: diffusion of specific particles through transport proteins found in the membrane a.Transport Proteins are specific – they “select” only certain molecules to cross the membrane b.Transports larger or charged molecules Passive Transport: Osmosis Osmosis: diffusion of water through a selectively permeable membrane Water moves from high to low concentrations  Hypotonic Solution Hypotonic: The solution has a lower concentration of solutes and a higher concentration of water than inside the cell. (Low solute; High water) Result: Water moves from the solution to inside the cell): Cell Swells and bursts open (cytolysis)!  Hypertonic Solution Hypertonic: The solution has a higher concentration of solutes and a lower concentration of water than inside the cell. (High solute; Low water) shrinks Result: Water moves from inside the cell into the solution: Cell shrinks (Plasmolysis)!  Osmosis Animations for isotonic, hypertonic, Isotonic Solution and hypotonic solutions Isotonic: The concentration of solutes in the solution is equal to the concentration of solutes inside the cell. Result: Water moves equally in both directions and the cell remains same size! (Dynamic Equilibrium) What type of solution are these cells in? A B C  How Organisms Deal with Osmotic Pressure Bacteria and plants have cell walls that prevent them from over-expanding. In plants the pressure exerted on the cell wall is called tugor pressure. A protist like paramecium has contractile vacuoles that collect water flowing in and pump it out to prevent them from over-expanding. Salt water fish pump salt out of their specialized gills so they do not dehydrate. Animal cells are bathed in blood. Kidneys keep the blood isotonic by remove excess salt and water.  How Cells Deal With Osmosis Plants: Turgor Pressure Water pressure that is exerted against cell wall  Plasmolysis – loss of turgor pressure Plants wilt Cytolysis – cells burst due to hypotonic solution cell is in  How Cells Deal With Osmosis Animal Cells: Contractile Vacuoles Collects water and expels it from the cell ACTIVE TRANSPORT  Active Transport cell uses energy in the form of ATP actively moves molecules to where they are needed Movement from an area of low concentration to an area of high concentration (Low à High) Types of Active Transport 1. Protein Pumps -transport proteins that require energy to do work Example: Sodium - Potassium Pumps are important in nerve responses. Types of Active Transport 2. Endocytosis: taking bulky material into a cell Uses energy Cell membrane in-folds around food particle “cell eating” forms food vacuole & digests food This is how white blood cells eat bacteria!  Types of Active Transport 3. Exocytosis: Forces material out of cell in bulk – process by which materials are released from the inside of the cell Release toxins and waste products Release proteins Cell changes shape – requires energy Example: Hormones or wastes released from cell WRITTEN WORK Review for 5 minutes