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SI session Oct. 4 Ch. 7 and 8 answers

SI session Oct. 4 Ch. 7 and 8 answers - Kaiser Imam October...

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Kaiser Imam October 4, 2007 BIOL 215 SI Session Chapters 7 and 8 Chapter 7:  Membrane Structure and Function  1. List the 5 principal functions of cellular membranes: 1) Boundary of the cell and selective permeability 2) Organization and localization of function 3) Transport processes 4) Signal reception 5) Cell-to-cell communication 2. Describe the components of the fluid mosaic model for membranes. The fluid-mosaic model suggests that proteins are randomly suspended in a phospholipid bilayer that surrounds the cell. It includes both phospholipids and membrane proteins. The phospholipids make up the “fluid” part while the proteins make up the “mosaic.” 3. What is an amphipathic molecule? Give an example. An amphipathic molecule has a polar end and a nonpolar end. An example is a phospholipid molecule. 4. What structure do phospholipids spontaneously form in an aqueous solvent? Phospholipids spontaneously arrange themselves to form a bilayer. 5. How does the polarity of phospholipids affect their position in membranes? The hydrophilic phosphate groups of phospholipids are in contact with water on the outer surfaces of membranes, while the hydrophobic fatty acid tails orient themselves toward the interior of the bilayer away from water. 6. What is the difference between phospholipid bilayers and micelles? Bilayers are made up of phospholipids with two fatty acid tails while micelles have phospholipids with only one fatty acid tail. When these single fatty acid phospholipids are added to water they spontaneously form a spherical micelle with the fatty acid tails pointed inward. The phospholipids of bilayers have two fatty acid tails that take up more space than in the fatty acids of micelles. Because of steric hindrance these phospholipids spontaneously arrange themselves in a bilayer rather than a ball. 1
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7. List some characteristics of each of the following types of lipids: 1) Phospholipids Glycerides: glycerol backbone, 2 fatty acids, phosphate head group Sphingolipids: sphingosine backbone, 1 fatty acid, phosphate head group 2) Glycolipids All include sphingosine backbone, 1 fatty acid, and sugar group Cerebrosides: single uncharged sugar as its carbohydrate group Gangliosides: charged oligosaccharide (multiple sugar monomers) carbohydrate group 3) Sterols Only found in eukaryotic membranes Contains 4 hydrocarbon rings and a polar hydroxyl group 8. Do the fatty acids attached to a phospholipid have to be the same? The fatty acids on a phospholipid do not necessarily have to be the same. This can affect the shape and orientation of the phospholipid in the bilayer. 9. What is membrane asymmetry? Membrane asymmetry refers to variable phospholipid compositions between the two layers of a membrane and the proteins associated with each. Basically, different types of lipids and membrane proteins are unequally distributed between the two monolayers.
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SI session Oct. 4 Ch. 7 and 8 answers - Kaiser Imam October...

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