Cell Cell Membrane & Membrane &

TransportTransport

Fluid mosaic model - Lipids, proteins & carbohydrates

Membrane trafficking - Passive Transport

- Active Transport

- Bulk Transport

Plasma Membrane - Plasma Membrane - Phospholipid BilayerPhospholipid Bilayer

Composition: - lipids, proteins & carbohydrates

Phospholipids, cholesterol & glycolipids - head: contains a polar phosphate group (hydrophilic) - tails: 2 nonpolar hydrocarbon fatty acid (hydrophobic)

Functions: - protection - controls traffic - selective permeable - anchoring/fusion

Fluid-Mosaic Model of Plasma MembraneFluid-Mosaic Model of Plasma Membrane

http://telstar.ote.cmu.edu/biology/downloads/membranes/index.html

Functions of Membrane Functions of Membrane ProteinsProteins

Membrane

Trafficking

Passive Passive TransportTransport

Simple diffusion: mov’t of molecules from a region

of high[ ] low

Concentration gradient: difference in [ ] b/t two regions - substances always move in the direction of the [ ] gradient

Membrane permeability of lipid bilayer- nonpolar vs polar molecules

O2 & CO2 can cross a lipid bilayer without help from membrane proteins – what properties allow this to

occur?

Diffusion PropertiesDiffusion Properties

Characteristics: not carrier-mediated, [ ] gradient & passive

Definitions: solution, solvent & solutes

Factors that influence rate of diffusion:

– temperature

– state of solvent

– size of molecules

– diffusion gradient

– membrane structure

So what So what is is solubilitsolubility?y?

OsmosisOsmosis

Diffusion of H2O across a selectively permeable membrane from a region of solute [ ] to a solute [ ] establish equilibrium

Osmotic pressure: pressure applied to the cell membrane from flow of H2O during osmosis -- # of particles in solution

Tonicity: the ability of a solution to cause a cell to gain or lose water

- isotonic, hypotonic & hypertonic

Facilitated Diffusion: Passive Facilitated Diffusion: Passive Transport Aided by ProteinsTransport Aided by Proteins

Carrier proteins

Primary active transport: movement of solutes against [ ] gradient biological membrane

- energy dependent

Na+/K+-ATPase pump:– resting membrane potential– osmotic balance– drives other pumps

Electrogenic pump

Active Active TransportTransport

+ + + + + + + + + + + + + +

- - - - - - - - - - - - - - - - - -

ATP

http://highered.mcgraw-hill.com/olc/dl/120068/bio03.swf