Chapter 5 Membrane composition and fluidity.

You Must Know Why membranes are selectively permeable. The structure and function of membrane proteins.

Amphipathic molecules Fluid Mosaic Model

Figure Mouse cell Human 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 Microfilaments of cytoskeleton Peripheral proteins Integral protein EXTRACELLULAR SIDE OF MEMBRANE CYTOPLASMIC SIDE OF MEMBRANE © 2014 Pearson Education, Inc.

Figure 5.5 Fluid Unsaturated tails prevent packing. Viscous Saturated tails pack together. (a) Unsaturated versus saturated hydrocarbon tails (b) Cholesterol reduces membrane fluidity at moderate temperatures, but at low temperatures hinders solidification. © 2014 Pearson Education, Inc. Cholesterol

Evolution of Differences in Membrane Lipid Composition Bacteria adapted to living in very hot conditions have more saturated fatty acids in their membranes © 2014 Pearson Education, Inc. Bacteria adapted to living in very cold conditions have more unsaturated fatty acids in their membranes