The movement of materials in and out of cells Ch 8 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 On both sides of membrane Osmosis stops “Equi” =Equal concentrations On both sides of membrane Osmosis stops Isotonic Solution

In Osmosis….only H2O moves 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

Osmosis in cells 10% salt solution -H20 +NaCl 1% salt solution + 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 organism in 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)