SI session Oct. 7 Ch. 7 and 8 answers

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

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Kaiser Imam October 7, 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. 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 1
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Contains 4 hydrocarbon rings and a polar hydroxyl group 5. 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. 6. 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. 7. List the three modes of movement of phospholipid molecules within membranes: 1) Lateral diffusion: movement within a single monolayer 2) Rotation: movement around a phospholipid’s central axis 3) Transverse diffusion (“flip flop”): movement between layers of a membrane 8. Why does transverse diffusion occur very rarely in lipid bilayers? Transverse diffusion, or “flip-flop”, is very rare because it is thermodynamically unfavorable for the hydrophilic heads of phospholipids to cross through the hydrophobic interior of a membrane. However, enzymes called phospholipid translocators, or “flippases” catalyze the movement of phospholipids from one monolayer to another. 9. What is the difference between saturated and unsaturated fatty acids? Saturated fatty acids have no double or triple bonds so that every carbon atom in the fatty acid chain has the maximum number of hydrogen atoms bonded to it. Unsaturated fatty acids have one or more double bonds in its structure, lowering the amount of hydrogen that can be bound. A polyunsaturated fatty acid has more than one double bond. 10. What configuration of double bonds is found in unsaturated fatty acids?
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This note was uploaded on 09/29/2009 for the course BIO 215 taught by Professor Diiulio during the Spring '09 term at Case Western.

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

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