Lecture 3 10

Lecture 3 10 - Lecture 3 10/03/07 Membrane Structure and...

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Lecture 3 10/03/07 Membrane Structure and Function Membranes are made of: Lipids Proteins Carbohydrates Functions of membranes: 1.) separation- compartmentalization 2.) permeability barriers-doesn’t allow everything to diffuse through it (e.g. hydrophobic barriers) 3.) facilitate transport- act on protein and ion trafficking in and out of cell Lipids make up 50% of membrane Phospholipids- ampiphatic molecules, have both hydrophobic and hydrophilic domains o Polar head group- hydrophilic o Two fatty acid tails- hydrophobic o There is a phosphate on polar head group Structure of Phospholipid: -Phospholipids can also have carbohydrates linked to polar head group glycolipids, important for cell signaling Characteristics of Membrane -Bilayers because of amphipatic phospholipids molecules -Fluid- can change their dynamic -Asymmetrical- inside and outside are not the same -Able to self assemble -Flexible How do we know?/Description of each characteristic 1.) Gorter and Grendel Experiment- Bilayer theory RBC put in distilled water RBC burst plasma membrane only (RBC “ghosts”, composed of nothing other than RBC PM) -Looked at plasma membrane Measured surface area of RBC Extracted lipids out of PM fraction (RBC ghost) made lipid monolayer compared monolayer surface area to surface area of RBC -Discovery: More monolayer surface area than measured surface area of RBC 2:1 Monolayer: RBC, so there are 2 layers of lipids, therefore a bilayer in plasma membrane 2.) Fluid Mosaic Model - Fluidity theory -UCSD research, 1972, by Singer and Nicolson
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Lecture 3 10 - Lecture 3 10/03/07 Membrane Structure and...

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