Cells Active & Passive transport

Phospholipid bilayer Made of Phospholipid molecules Heads (polar) Tails (nonpolar) Form impermeable barrier

Fluid Mosaic Model Fluid  Bilayer has “fluid” consistency  molecules “float” “Mosaic”  Proteins, Carbs & Lipids “float” in bilayer

Selective Permeability Some substances can get through, some cannot Glucose & other ions, molecules have to use transport proteins

Passive & Active Passive Active Movement of molecules in and out of the cell Does not require energy Moves stuff with the Concentration Gradient Two types OSMOSIS DIFUSION Active Movement of molecules in and out of the cell Requires energy (ATP) Requires some type of protein Moves stuff against the Concentration Gradient

Passive Transport Diffusion Molecules are driven by molecular motion/collisions

Passive Transport Diffusion Molecules move from  to  concentration  equilibrium Solutes may be: Molecules (solid, liquid or gas) Ions (cations [+], anions [-]) Solvent (biological) is water How O2 & CO2 pass in & out of cell membrane

Passive Transport Osmosis Diffusion of solvent molecules (usually water) Tonicity: Ability of surrounding solns to cause cells to gain/lose water Osmoregulation-control of water balance

Hypertonic Higher concentration on solutes (which means lower concentration of SOLVENT…aka water) Cells SHRINK in a Hypertonic solution

Hypotonic SOLUTE concentration is lower (and SOLVENT concentration is higher) Cells SWELL in a hypotonic solution

Isotonic SOLUTE concentration is the same inside and outside the cell (so is the SOLVENT)  Equilibrium Cells don’t change size in Isotonic solutions

Passive Transport Results

Facilitated Diffusion Imbedded protein helps move molecules across membrane Doesn’t require energy (still high to low) Some hydrophilic Other hydrophilic molecules can pass through

Active Transport Moves substance against concentration gradient “Carrier-mediated”—always uses a carrier protein Always requires addition of energy P Protein changes shape Phosphate detaches ATP ADP Solute Transport protein

Active Transport Na+/K+ pump With the help of ATP, the carrier protein changes shape 3 Na+ leave cell 2 K+ enter cell 1/3 of all the energy used by cells is used to drive the Na+/K+ pump!

Enzymatic Proteins Enzymes that are bound into the membrane Carry out reactions Ex. ATP Synthase  generate ATP

“Bulk” Transport Endocytosis Phagocytosis: Ingestion of large molecules Pinocytosis: Ingestion of small molecules or liquid

“Bulk” Transport Exocytosis Vesicles fuse with plasma membrane and “dump” contents! Eliminate wastes Secretion of molecules Contractile vacuoles Fluid outside cell Cytoplasm Protein Vesicle