Cellular Transport

Cellular Transport The movement of materials in and out of cells Ch 8

Cellular Transport • What substances move ? • How do they move? • What is the membrane structure? • What is passive versus active transport?

Solution Concentration: • Like density = • # molecules per • volume of container • Low or High Concentration * * * * * * * * * ** * * * ** * * * * High Conc. * * * * * * * * Low Conc.

Diffusion • Movement of molecules: • gas or liquid • Law of Diffusion: • From High Concentration to • Low Concentration

Diffusion of gases……. O2 High CO2 CO2 High

Cell Membrane • Surrounds cells • Gives shape to animal cells • Inside cell wall of plant cells

Cell Membrane Made of: • Lipid layer • Protein channels • Semi-permeable

Cell Membrane

Semi-permeable: • Semi= “some” substances may pass • Selective • Based upon size & solubility H20 flows Salt remains

Osmosis • Movement of water • Across a semi-permeable membrane • Special case of diffusion

Equilibrium H2O H2O H2O H2O H2O H2O H2O H2O H2O • “Equi” =Equal concentrations • On both sides of membrane • Osmosis stops • Isotonic Solution

Therefore focus on the water concentration: 1% Salt solution Water is High concentration Salt is Low 10% Salt Solution Water is Low concentration Salt is High In Osmosis….only H2O moves

Osmosis in cells • 10% salt solution • -H20 • +NaCl 1% salt solution + H20 -NaCl H20 H20 Water flows from High to Low Concentration

Active or Passive Transport? • Which requires ATP energy? • Which goes with the concentration gradient? • Which goes against the gradient?

Concentration Gradient * * * * * * * * * * * *

Passive Transport • Diffusion or Osmosis • Going with the gradient • No ATP energy required High Conc. To Low Conc. * * * * * * * * * * * * * * * * * * * *

Active Transport • Against the gradient • Requires ATP • Low to High Concentrations • Salt returning to blood in kidneys * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

Plasmolysis • Cell membranes shrink or expand • Dependent on salt concen-trations

Hypotonic or Hypertonic Solutions? Tap Water • Hypotonic = “under” or low salt outside, relative to cell • Hypertonic = “over” or high salt relative to cell Salt water inside cell

Sea water organism in fresh water………………. Tap Water • Hypotonic Solution = • Low salt concentration outside the cell • High Water concentration outside • Water moves? • Inside • Cell Bursts! • Salt Water • Inside Cell • Low Water H20

Fresh water organismin salt water…………. • Hypertonic Solution • Water moves? • Out of the cell • Cell shrinks • Salt Water • High salt • Low water • Fresh water • Inside cell= • High Water H20

Plants cells bulge, not burst! Or Cell Membranes Shrink

Paramecium have water pumps!(called contractile vacuoles)

Cellular Transport