1. TRANSPORT ACROSS MEMBRANES THE WAY CELLS REGULATE THEIR CONTENTS

2. TWO MAJOR TYPES OF TRANSPORT zPASSIVE: Only from high concentration to low zACTIVE: Can actually pump up a gradient using energy from some other source such as ATP (Primary) or another gradient (Secondary)

3. Passive Transport zDiffusion zBulk Flow zElectrodiffusion zCurrent Flow zOsmosis zFacilitated Diffusion

4. Diffusion zDiffusion occurs when concentration in one region is greater than in another zThe end result is an even distribution called equilibrium Before: After:

5. Diffusion across a permeable membrane zDiffusion occurs when concentration in one region is greater than in another zThe end result is an even distribution called equilibrium Before: After:

6. Impermeable membrane zDiffusion can not occur Before: After:

7. Bulk Flow zAnalogous to the flow of water through a pipe zThrough pores in membranes zThrough blood vessels zThrough other tubular structures

8. Current Flow + - POSITIVE REGIONNEGATIVE REGION CATIONS AND ANIONS MOVE IN OPPOSITE DIRECTIONS CARRYING ELECTRICAL CURRENT CURRENT = FLOW OF CATIONS - FLOW OF ANIONS

9. Osmosis z SOLUTE NO SOLUTE NO SOLUTE Before: After: Water moves across a semi-permeable membrane to the side where the solute is most concentrated

10. Facilitated Diffusion z1. Molecule binds to carrier z2. Carrier changes conformation z3. Molecule released on other side z4. Purely passive process- stops when concentrations are equal

11. ACTIVE TRANSPORT REQUIRES AN INPUT OF ENERGY zUSUALLY IN THE FORM OF ATP zATPase IS INVOLVED zSOME ASYMMETRY IS NECESSARY zCAN PUMP UPHILL

12. ACTIVE TRANSPORT ADP ATP