chapter 5 membrane composition and fluidity.. you must know why membranes are selectively permeable....
TRANSCRIPT
You Must Know
• Why membranes are selectively permeable.
• The structure and function of membrane proteins.
Amphipathic molecules
Fluid Mosaic Model
Figure 5.4-1
Mouse cellHuman cell
Membrane proteins
The Fluidity of Membranes
Membranes must be fluid to work properly; they are usually about as fluid as salad oil.
Figure 5.2
Glyco-protein
Glycolipid
Fibers of extra-cellular matrix (ECM)
Carbohydrate
Cholesterol
Microfilamentsof cytoskeleton
Peripheralproteins Integral
protein
EXTRACELLULARSIDE OF
MEMBRANE
CYTOPLASMIC SIDE OF MEMBRANE
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Figure 5.5
Fluid
Unsaturated tails preventpacking.
Viscous
Saturated tails packtogether.
(a) Unsaturated versus saturated hydrocarbon tails
(b) Cholesterol reducesmembrane fluidity atmoderate temperatures,but at low temperatureshinders solidification.
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Cholesterol
Evolution of Differences in Membrane Lipid Composition
• Bacteria adapted to living in very hot conditions have more saturated fatty acids in their membranes
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• Bacteria adapted to living in very cold conditions have more unsaturated fatty acids in their membranes