03-Biological membranes notes

03-Biological membranes notes - Plasmamembrane

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Biological membranes Plasma membrane - Keeps the distinction between inside and outside - The exterior wall of the cell - Membrane is both a barrier, and selective “door” to the cell - We need to transport things in and out and communicate - Very complex regulator of cell contents, of things going in and out - “Semipermeable” barrier—some molecules with certain properties diffuse  easily, others with different properties don't Questions to think about - What is the membrane permeable to? What is it made of? What comes in  and out?  - What chemical properties regulate this? How can we predict if a molecule  is permeable or not? - What is the role of diffusion in determining cell contents? - Can we move impermeable substances? What type of molecules have to aid  the process? - What is the role of H 2 O? Does it go through the membrane? How do we  deal with water and the solubility of the membranes and the things that go  in/out of membrane? Phospholipid structure - Phospholipids are amphipathic  due to their dual hydrophobic/hydrophilic  parts - Spontaneously group together - Aggregates of phospholipids form cell membranes - Cell membrane chemistry is dominated by the hydrophobic properties of  phospholipids - Figure 5.1b - Hydrophobic tail, hydrophilic head - Tails interact w/ each other, heads interact w/ water Membrane structure - Physical nature of the membrane – chemical analysis: phospholipids - What is the structural arrangement? - Monolayer? (like a micelle) - Bilayer?
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Gorter and Grendel experiment - Membrane structure experiment - Obtain a sample of RBCs (red blood cell) from an animal - cell count - Determine the surface area of a RBC - Estimate total surface area of these cells (sa of RBC x cell count = total  sa) - Isolate the phospholipids from all RBCs, measure surface area of RBCs - Determine the surface area of a monolayer of lipids - if it was a micelle, the surface area should be same as phospholipids - if it was bilayer, it should be double the sa of phospholipids - Calculate the ratio Gorter and Grendel data (table) Animal #RBCs Surface area  of 1 RBC Surface area of  all RBCs Surface area of  all phospholipids ratio Sheep 9,900 29.8 295,000 620,000 2.1 Rabbit 5,900 92.5 546,000 990,000 1.8 Goat 16,500 17.8 294,000 617,400 2 Dog 6,800 90 612,000 1,224,000 2 Man 4,700 99 465,000 883,500 1.9 Membrane is bilayered
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- special tray holds water, we can push bar back and forth - when we isolate phospholipids, they spread - as we slide bar to the left, the phospholipids will be pushed together - bar detects resistance, this means the phospholipids are packed as densely  as possible - calculate distance - Allows measurement of area of monolayer
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This note was uploaded on 03/25/2010 for the course BIO 11000 taught by Professor Friedman during the Spring '10 term at Purdue.

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03-Biological membranes notes - Plasmamembrane

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