BIOL 215 Final Exam Review - Chapters 8-11 answers

BIOL 215 Final Exam Review - Chapters 8-11 answers - Kaiser...

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Kaiser Imam December 14, 2007 BIOL 215 Final Exam Review Chapters 8-11 Chapter 8: Membrane Transport 1. List some factors affecting the rate of diffusion of molecules across lipid bilayers: 1) Size: bilayers are more permeable to smaller molecules 2) Polarity: bilayer is more permeable to nonpolar molecules since they can cross through the hydrophobic interior of the membrane 3) Ionic: bilayer highly impermeable to ions 2. What is the difference between diffusion and osmosis? Diffusion involves the passive transport of a solute molecule from an area of high concentration to low concentration. Osmosis can be considered the passive diffusion of water. Osmosis involves the movement of water through a semipermeable membrane from an area of low solute concentration to an area of high solute content. 3. What is the difference between a carrier protein and a channel protein? A carrier protein has to physically bind to a solute on one side of a membrane and change conformation to release the solute on the other side. Channel proteins are different because they form a usually hydrophilic channel through which solutes can pass without having to change the conformation of the channel protein. 4. Describe each of the following types of carrier proteins: a) Uniporter Transports a single molecule of solute across the membrane at the time. An example is the GLUT1 glucose transporter in erythrocytes. b) Symporter Transports two solutes in the same direction. An example is the Na + /Glucose symporter. c) Antiporter Transports two solutes in opposite sides of the membrane. An example is the Na + /K + antiporter. 5. What is the difference between direct and indirect active transport? In direct active transport the movement of a solute molecule or ion is directly coupled to an exergonic chemical reaction such as the hydrolysis of ATP. Indirect active transport depends on the simultaneous transport of two solutes, with the movement of one solute down its gradient driving the movement of the other up its gradient. 1
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6. Describe the following types of ATPases involved in active transport: a) P-Type ATPases: are reversibly phosphorylated by the phosphate molecule from ATP as part of the transport mechanism b) F-Type ATPases: generates H + gradient that drives ATP synthesis. The pumps essentially run in reverse and function as ATP synthases, producing ATP as well as consuming it. c) ABC-type ATPases: stands for “ATP binding cassette.” Found in some bacteria and can be used to pump drug molecules out of the cell. Also found in some tumors where they can be used to pump out chemotherapy drugs. 7. Explain the mechanism of the Na + /K + pump. The Na + /K + pump moves 3 Na + ions out of the cell and 2 K + inside. The protein starts in the E 1 conformation in which it is open to the inside of the cell and its sodium binding sites are available for binding. Three Na + ions bind to the protein, after which a molecule of ATP is hydrolyzed and the phosphate is attached to the pump. This causes a conformational change
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