Cell Membranes

CELL MEMBRANES ,[object Object],This is an introduction to the structure and function of cell membranes. It is designed to be a self-contained unit with links to other, related material. www.freelivedoctor.com

THE FUNCTION OF CELL MEMBRANES ,[object Object],[object Object],[object Object],It is thought by some that the spontaneous organization of membranes played an important role in the evolution of life . www.freelivedoctor.com

PHOSPHOLIPIDS: The “Backbone” of the Membrane Cartoon of a phospholipid molecule This cartoon depicts the basic amphipathic* structure common to all phospholipids * both polar and non-polar regions Fatty acids Glycerol plus polar side group www.freelivedoctor.com

WATER MOLECULES ARE POLAR ,[object Object],[object Object],O H H + + d d/2 d/2 + Oxygen pulls electrons towards itself causing a charge imballance (d-) www.freelivedoctor.com

Water is a good solvent for polar molecules and ions - + - + - + - + - + Hydration Shells - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + www.freelivedoctor.com Na + Cl - - + - + - + - + - + - +

PHOSPHOLIPIDS ,[object Object],Polar head (Hydrophilic- likes water) Non-polar tail (Hydrophobic- hates water) www.freelivedoctor.com

OIL/WATER PARTITION: THE “KITCHEN” EXPERIMENT MIX OIL WATER AND TEST SUBSTANCE WATER CONCENTRATION OF TEST SUBSTANCE IN OIL/ CONCENTRATION OF TEST SUBSTANCE IN WATER = OIL WATER PARTITION COEFFICIENT (OWPC=K) K > 1 HYDROPHOBIC (NON-POLAR) K < 1 HYDROPHILIC (POLAR) www.freelivedoctor.com WAIT OIL

MIXING PHOSPHOLIPIDS AND WATER: Spontaneous Self-Organization www.freelivedoctor.com

MIXING PHOSPHOLIPIDS AND WATER: Spontaneous Self-Organization Click ahead www.freelivedoctor.com

Phospholipids plus water make a self-organizing system ,[object Object],[object Object],[object Object],www.freelivedoctor.com

Micelle Sheet www.freelivedoctor.com

The Black Lipid Membrane (BLM) ,[object Object],[object Object],[object Object],[object Object],www.freelivedoctor.com

The Black Lipid Membrane (BLM) ,[object Object],What you see Light Source Microscope Outer Beaker Inner Beaker www.freelivedoctor.com

Permeability of the BLM mol/sec-sq. cm. www.freelivedoctor.com

The Black Lipid Membrane Could be used to Show what else is in Cell Membranes ,[object Object],[object Object],[object Object],www.freelivedoctor.com

The membrane is fluid www.freelivedoctor.com

Cholesterol sits between fatty tails www.freelivedoctor.com

Proteins can span the bilayer Hydrophilic Hydrophobic www.freelivedoctor.com

The fluid-mosaic model ,[object Object],[object Object],[object Object],www.freelivedoctor.com

The fluid-mosaic model www.freelivedoctor.com

Channels and carriers are needed to get ions across the bilayer www.freelivedoctor.com

Cell Membranes Become Network Elements in Tissue Membranes ,[object Object],[object Object],[object Object],www.freelivedoctor.com

An Epithelial Membrane in Cartoon Form: www.freelivedoctor.com

A Network Model of Coupled Salt and Volume Flow Through an Epithelium AM TJ BM BL CL PL CB PB CELL LUMEN BLOOD www.freelivedoctor.com

What to do now? ,[object Object],[object Object],www.freelivedoctor.com

Cell Membranes

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