Maintaining HomeostasisPassive and Active Transport

Lesson Objectives •Understand how equilibrium is established

as a result of diffusion.

•Distinguish between diffusion and osmosis.

Cellular Membrane•Membrane: function is to control what

enters and exits the cell

▫Selectively permeable

Homeostasis•All living cells exists in a liquid

environment•Internal conditions need to remain

constant▫Homeostasis▫Equilibrium=everything is balanced

•Maintain homeostasis by regulating movement of molecules across the membrane▫Passive Transport (no energy required)▫Active Transport (energy required)

Passive Transport: Diffusion•Movement of materials across the cell

membrane without using energy•Diffusion:

▫Movement of material/molecules from an area of high concentration to an area of low concentration Concentration Gradient

Passive Transport: Osmosis•When water diffuses across the cell

membrane

• http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html

Effects of Osmosis on CellsHypotonic:•Lower solute

concentration outside of the cell

▫Water moves into the cell

▫Cell swells

Hypertonic:•Higher solute

concentration outside of the cell

▫Water moves out of the cell

▫Cell Shrinks

Isotonic:•Concentration

is the same inside and out

▫Water moves in and out

How does water move? “Salt Sucks”

How does water move? “Salt Sucks”

v v

How does water move? “Salt Sucks”

Osmosis In Nature•Cytolysis: in a hypotonic solution red blood

cells will continue to swell until they burst▫Penicillin killing bacteria

•Contractile Vacuole: organelle in protist cells that pumps excess water out ▫ http://www.youtube.com/watch?v=pahUt0RCKYc&feature=relat

ed

•Turgor Pressure: water pressure placed on the cell wall to give plant cell its shape▫Plants wilting if solution is hypertonic

•Don’t drink salt water•Diarrhea

▫Something in stools that is drawing out the water

Facilitated Diffusion•Movement of particles from higher

concentration to lower concentration•Large molecules may require “help”, they

use carrier proteins•Nervous system uses Na and Ca pumps

Lesson Objectives•Distinguish between passive and active

transport.

•Explain how sodium-potassium pumps operate.

•Compare and contrast endocytosis and exocytosis.

Active Transport

Passive Transport: down concentration gradient

Active Transport

Active TransportPassive Active

Active Transport•Requires energy to move molecules up

their concentration gradient▫Low concentration to high concentration

•Sodium-Potassium Pump•Exocytosis•Endocytosis

Cell Membrane Pumps•Requires a carrier protein •3 Na-2 K

•Requires energy

• http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html

Endocytosis•Phagocytosis•Pinocytosis

Exocytosis