1. Name the three basic parts of a cell and describe the functions of each. 2. Why do phospholipids organize into a bilayer – tail-to-tail – in a watery environment?

Hypertonic, isotonic, or hypotonic? 1. What type of fluid might be infused into the bloodstream of a patient who needs fluid drawn out from swollen tissues? 2. What type of fluid might be used (carefully) to rehydrate the tissues of extremely dehydrated patients? 3. In a U-tube separated by a selectively permeable membrane, there is.2 M glucose in Side A, and.4 M glucose in Side B. Side A is ____ compared to Side B, and Side B is ____ compared to Side A. 4. If the membrane in #3 is only permeable to water, what will happen?

Part 2: Membrane Transport

Interstitial fluid Interstitial fluid:  Fluid outside cells  Rich, nutritious “soup” – amino acids, sugars, fatty acids, vitamins, hormones, salts, wastes Selective Permeability Selective Permeability:  Plasma membrane only allows some substances to enter cell  Nutrients in, wastes out passive active  By passive or active transport

 No energy (ATP) needed down concentration gradient  Molecules move down concentration gradient from HIGH  LOW concentration  Types: diffusion, filtration

 Nonpolar & lipid-soluble substances  Nonpolar & lipid-soluble substances diffuse directly through lipid bilayer  Eg. O 2, CO 2, fat-soluble vitamins

 Transport proteins  Transport proteins (carrier or channel proteins) assist molecules across membrane  Eg. glucose, amino acids, H 2 O, ions

 Water-filled channels  Eg. ions

 Binds to molecule, changes shape, ferries it across membrane  Eg. glucose transporter

 Diffusion of H 2 O  Aquaporins:  Aquaporins: channel proteins for H 2 O passage

 Ability of solution to change shape or tone of cells by changing water volume  Isotonic  Isotonic = equal concentration solutes  Hypertonic  Hypertonic = higher conc. of solutes  Hypotonic  Hypotonic = lower conc. of solutes

 Energy (ATP) is needed!! against concentration gradient  Move molecules against concentration gradient from LOW  HIGH concentration  Types: Primary and Secondary

ATP  Directly uses ATP to drive transport  Eg. Ca 2+ pump, H + pump, Na + -K + pump

Sodium-Potassium Pump

 Move more than 1 substance at a time  Symport  Symport: 2 substances moved in same direction  Antiport  Antiport: 2 substances cross in opposite directions  Eg. cotransport of sugars, animo acids, ions

vesicles  Fluid & large particles transported across membranes in vesicles (sacs)  Exocytosis  Exocytosis: “out of cell” – eject substances  Endocytosis  Endocytosis: “within the cell”- ingest substances

 Phagocytosis  Phagocytosis: (cell eating) – engulf large or solid material  eg. WBC engulf bacteria

 Pinocytosis  Pinocytosis: (cell drinking) – fluid w/dissolved molecules  Eg. intestinal cells

 Receptor-mediated endocytosis ligands receptor proteins  Receptor-mediated endocytosis: concentrate specific substances (ligands) that bind to receptor proteins  Eg. insulin, iron, cholesterol