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Homeostasis & Transport

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Chris Maltby

on 14 November 2014

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Transcript of Homeostasis & Transport

Passive Transport
Homeostasis & Transport
(cc) photo by Metro Centric on Flickr
(cc) photo by jimmyharris on Flickr
(cc) photo by Metro Centric on Flickr
The Quest for stability
Cell membranes are selectively permeable.
Some things cross without energy input from the cell.
Diffusion: The movement of molecules from an area of higher concentration to an area of lower concentration
Concentration Gradient: The difference in the concentration of molecules across a space.
Kinetic Energy: Drives diffusion.
Molecules move "down" their gradient and then keep moving once they are evenly distributed.
Equalibrium: when the concentration of molecules is the same throughout a given space.
Diffusion Across Membranes
Molecules that dissolve in Lipids (think phospholipid bilayer) can diffuse across cell membranes.
Oxygen and Carbon dissolve in lipids (because of their non-polar nature)
Very small molecules that cannot dissolve in lipids also diffuse by moving through the pores.
The process by which water molecules diffuse across a cell membrane from an area of higher concentration to an area of lower concentration
The direction of osmosis depends on the concentration of solutes on the two sides of the cell membrane
Hypotonic: when the solute concentration is LOWER outside the cell than in the cytosol.
Hypertonic: when the solute concentration is HIGHER outside the cell than in the cytosol
Isotonic: when the solute concentration is EQUAL outside the cell and in the cytosol.
How Cells Deal With Osmosis
Isotonic Environment Dwellers-- (vertabrates on land and most organisms in the sea)

They do nothing special.
Hypotonic Dwellers (unicellular freshwater organisms)

Contractile Vacuoles -- Vacuoles that rid the cell of water. I.E. The Paramecium.
Plant Cells -- example :roots

The cell wall is strong enough to stop too much water entering the cell.
Turgor Pressure -- the pressure water exerts on the cell wall.
Hypertonic Dwellers

Plasmolysis -- When a plant cell losses water and the cell membrane shrinks from the wall.
Red Blood cells -- no vacuoles or pumps. Shrink and swell.
Cytolysis -- when cells burst due to a hypotonic (lower outside) gradient.
Turgor Pressure
Contractile Vacuole
Osmosis: The Movie
The End!
Facilitated Diffusion
Diffusion Through Ion Channels
Active Transport
Requires energy.
Moves things up the concentration gradient.
From lower concentration to higher.
Cell Membrane Pumps
Sodium-Potasium Pumps
Endocytosis & Exocytosis (Fueled by ATP).
Review: Passive Transport Types
Diffusion Across Cell Membranes
Facilitated Diffusion
Diffusion Through Ion Channels
Diffusion Through Ion Channels
Facilitated Diffusion
Specific Membrane Proteins move molecules that cannot diffuse.
They change shape.
I.E. Glucose or Amino Acid transport.
Carrier proteins can only move molecules they are designed to move.
Def. Ion: An atom or molecule that has a negative or positive charge from losing or gaining electrons (-).
Sodium (Na+)
Potassium (K-)
Calcium (Ca2+)
Chloride (Cl-)
Moves Na+ & K+ ions up the gradient
Animal cells need more NA+ outside.
Animal cells Need more K+ inside.
ATP from the mitochondrion provides energy.
The Sodium-Potasium Pump
(Fueled by ATP)
Endocytosis: the process in which cells ingest material.
Vessicles -- the pouch of cell mambrane that surrounds the particles.
Pinocytosis: transport of solutes or fluid.
Phagocytosis: transport of large particles or whole cells.
Endocytosis & Exocytosis
Exocytosis:The release of materials outside the cell.
I.E. Proteins from the ribosomes.
Review: Active Transport Types.
Cell Membrane Pumps (NA-K).
Full transcript