Chapter 3 – pp Unit III: Lively Molecules Movement of Molecules

Interstitial fluid Ions Glucose Blood protein Amino acid Capillary hydrostatic pressure (CHP) Filtration Particles are driven through a selectively permeable membrane by water Moves material between cells not thru Examples: coffee filter, blood capillaries Endothelial cell 1 Endothelial cell 2 Water molecule Hydrogen bond Small solutes

Simple Diffusion Passive transport Random motion of solutes Rates depend on: – Temperature – Size of the molecule – Distance – Concentration gradient how a cell acquires nutrients and gets rid of wastes Diffusion and Osmosis

Diffusion Down gradient Eventually becoming uniform Brownian Motion – random motions of microscopic particles caused by collisions with moving molecules Example: a drop of dye in water

Diffusion and Osmosis Osmosis Special type of diffusion: – the diffusion of water molecules across a semi-permeable membrane

Diffusion and Osmosis Osmosis Osmotic pressure = Hydrostatic pressure to halt osmosis Osmotic pressure is proportional to the solute concentration Example:

Diffusion and Osmosis Osmosis Example: Red blood cells placed in a drop of distilled water will swell and burst Explanation: The distilled water is hypotonic to the RBC’s cytoplasm (a) Hypotonic

Diffusion and Osmosis Osmosis Example: Red blood cells placed in a drop of highly concentrated salt solution will shrivel up Explanation: The salt solution is hypertonic to the RBC’s cytoplasm

Diffusion and Osmosis Osmosis Example: Red blood cells placed in a drop of blood plasma – no change. Explanation: The blood plasma is isotonic to the RBC’s cytoplasm

Diffusion and Osmosis Osmosis Osmolarity – total solute concentration in an aqueous solution Tonicity – description of how the solution effects a cell Example situation: giving large volume of fluid during blood loss or dehydration. – Osmolarity starts the same but ECF is ______________ – Ions (thus water) moves in to ICF to equilibrate ↑ osmolarity – Administer: ________________

Carrier – Mediated Transport Cell membrane is essential Employ transport proteins/carriers Specificity Saturation Other Membrane Transports Concentration of solute Rate of solute transport (molecules/sec passing through plasma membrane) Transport maximum (T m )

Facilitated Diffusion Down gradient No ATP used Carrier – Mediated Transport

Active Transport Up gradient ATP energy required to change carrier Examples: –sodium-potassium pump –bring amino acids into cell –pump Ca 2+ out of cell

Carrier – Mediated Transport Active Transport Sodium-Potassium Pump Needed because Na + and K + constantly leak through membrane One ATP utilized to exchange three Na + pushed out for two K + brought in to cell

Carrier – Mediated Transport Active Transport Sodium-Potassium Pump CYTOPLASM Glucose molecule Sodium ion Na + –K + pump + + Regulation of cell volume Heat production Maintenance of a membrane potential Secondary active transport (No ATP used)

Vesicular Transport Transport large particles or fluid droplets through membrane in vesicles Endocytosis – –phagocytosis – –pinocytosis – –receptor mediated endocytosis – Exocytosis – Bacterium Pseudopodium Phagocytosis Lysosome Golgi apparatus Exocytosis