Chapter 5 Membrane composition and fluidity.

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

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.

Amphipathic molecules Fluid Mosaic Model

Figure 5.2 Glyco- protein Glycolipid Fibers of extra- cellular matrix (ECM) Carbohydrate Cholesterol Microfilaments of cytoskeleton Peripheral proteins EXTRACELLULAR SIDE OF MEMBRANE CYTOPLASMIC SIDE OF MEMBRANE Integral protein © 2014 Pearson Education, Inc.

Which of the amino acids below would you be more likely to find in section “A” of the protein? Integral protein A

Which of the amino acids below would you be more likely to find in section “B” of the protein? Integral protein B

Figure 5.5 Fluid Unsaturated tails prevent packing. Viscous Saturated tails pack together. 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 Would bacteria adapted to living in very hot conditions have more saturated or unsaturated fatty acids in their membranes? © 2014 Pearson Education, Inc. Unsaturated tailsSaturated tails

Evolution of Differences in Membrane Lipid Composition Would bacteria adapted to living in very cold conditions have more saturated or unsaturated fatty acids in their membranes? © 2014 Pearson Education, Inc. Unsaturated tailsSaturated tails

Evolution of Differences in Membrane Lipid Composition The ability to change the lipid compositions in response to temperature changes has evolved in organisms that live where temperatures vary. © 2014 Pearson Education, Inc.