Cellular Transport Notes

Structure of the Cell Membrane Outside of cell Carbohydrate chains Proteins Lipid Bilayer Transport Protein Phospholipids Inside of cell (cytoplasm) Animations of membrane structure Go to Section:

Types of Cellular Transport Animations of Active Transport & Passive Transport high low Weeee!!! Passive Transport cell does NOT use energy Diffusion Facilitated Diffusion Osmosis Active Transport cell does use energy NA+ K Pump Endocytosis Exocytosis high low This is gonna be hard work!!

Passive Transport (HighLow) no energy required molecules move randomly Molecules spread out from an area of high concentration to an area of low concentration. (HighLow) Food coloring in water demo

3 Types of Passive Transport Diffusion Facilitative Diffusion – diffusion with the help of transport proteins Osmosis – diffusion of water

Simple Diffusion Animation 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 http://bio.winona.edu/berg/Free.htm

Facilitated diffusion (Channel Protein) Diffusion (Lipid Bilayer) diffusion of specific particles through transport proteins found in the membrane Transport Proteins are specific – they “select” only certain molecules to cross the membrane Transports larger or charged molecules Facilitated diffusion (Channel Protein) Diffusion (Lipid Bilayer) Carrier Protein http://bio.winona.edu/berg/Free.htm

Facilitated Diffusion Glucose molecules Cellular Transport From High High Concentration Channel Proteins animations Cell Membrane Low Concentration Protein channel Low Transport Protein Through a  Go to Section:

Osmosis Osmosis animation diffusion of WATER through a semi- permeable membrane Water moves from high to low concentrations Water is so small and there is so much of it the cell can’t control it’s movement through the cell membrane. Water moves freely through pores. Solute (green) too large to move across.

Tonicity The concentration of solutions (usually one inside a cell and the other outside the cell, that determine direction and amount of diffusion

Osmosis Animations for isotonic, hypertonic, and hypotonic solutions There is less solutes outside the cell than there is inside the cell (hypo = low/less) Result: Water moves from the solution to inside the cell (to dilute the solutes)- Cell Swells and bursts open (cytolysis)!

Osmosis Animations for isotonic, hypertonic, and hypotonic solutions Hypertonic Solution There is more solutes outside the cell than there is inside the cell (hyper = higher/more) shrinks Result: Water moves from the cell into the solution (to dilute the solutes) Cell shrinks (Plasmolysis)!

Osmosis Animations for isotonic, hypertonic, and hypotonic solutions Isotonic Solution 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)

B C A What type of solution are these cells in? Hypertonic Isotonic Hypotonic

Active Transport (Low  High) cell uses energy actively moves molecules to where they are needed Movement from an area of low concentration to an area of high concentration (Low  High)

Sodium / Potassium Pump (Na+ / K+) Sodium Potassium Pumps (Active Transport using proteins) Pumps are carrier/transport proteins that require energy to move substances UP their concentration gradient. Sodium / Potassium Pumps are important in nerve responses. Transports 3 Na ions out of cell and 3 K ions into the cell Prevents Na ions from building up in the cell which would lead to osmosis into the cell and eventual bursting of the cecll Protein changes shape to move molecules: this requires energy!

Mass Transport Across a Membrane Vesicles Many substances, such as proteins, polysaccharides, and even bacteria, are too large to be transported by carrier proteins altogether. Instead, they cross the cell membrane in vesicles, which are membrane-bound (lipid bi-layer) sacs. vesicles can bud off from the membrane, fuse with it, or fuse with other vesicles.

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!

Endocytosis & Exocytosis animations Forces material out of cell “cell-pooping” membrane surrounding the material fuses with cell membrane Cell changes shape – requires energy EX: Hormones or wastes released from cell