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SI session Nov. 6 Ch. 14 answers

SI session Nov. 6 Ch. 14 answers - Kaiser Imam November 6...

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Kaiser Imam November 6, 2007 BIOL 215 SI Session Chapter 14 Chapter 14: Signal Transduction 1. A substance that fits into a specific binding site on a receptor protein is called a __ ligand __. 2. Another name for this type of molecule is a __ primary messenger __ because it binds to the __ outside __ surface of the cell to start the signal transduction pathway. 3. A __ second messenger __ is a substance produced inside the cell after the binding of a ligand to carry on the signal transduction pathway. 4. __ Endocrine __ signals are molecules that are released into the bloodstream to reach far away target cells. A general example of this type of signal includes __ hormones __. 5. __ Local mediators __ are signals secreted by cells into their immediate area to communicate with nearby cells. Another name for this type of signaling is __ paracrine signaling __. 6. The __ adrenal __ glands, located on top of the __ kidneys __, produce the hormones epinephrine and norepinephrine. 7. The enzyme that breaks down glycogen in the liver is called __ glycogen phosphorylase __. 8. What are the two main reasons cells utilize signal transduction pathways? 1) Signal amplification: one molecule of receptor can activate many more molecules down the cascade. 2) Ligands usually cannot pass through the membrane. 9. What is the significance of Earl Sutherland’s 1956 experiment on signal transduction pathways? Describe the procedure of the experiment. In his 1956 experiment Earl Sutherland was testing the effect of epinephrine on the enzyme glycogen phosphorylase, the enzyme that breaks down glycogen to glucose. He found that adding epinephrine to intact cells resulted in the activation of the enzyme. However, after he homogenized the cells (disrupted the plasma membrane) he found that the addition of epinephrine did not activate glycogen phosphorylase, even though the enzyme would be in direct contact with epinephrine once the cells had been lysed. Sutherland concluded that epinephrine did not directly affect its target enzyme. Rather, epinephrine was simply part of a signal transduction pathway that uses a system of second messengers to cause changes in 1
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the cell. An intact cell is needed to perform these pathways. Sutherland also found the role of cAMP, the first second messenger to be discovered. 10. Describe the effects of epinephrine on the following types of tissue: a) Cardiovascular tissue Increases heart rate and blood pressure b) Adipose cells Accelerates the production of fatty acids c) Muscle and liver cells Glycogen degradation 11. Why does epinephrine have different effects on different cell types? Each type of cell has a different response to epinephrine that involves a different signal transduction pathway. This includes using different second messengers and activating different enzymes. Also, in these cells the expression of different sets of genes can be modified, making the cells perform specific activities depending on their functions.
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SI session Nov. 6 Ch. 14 answers - Kaiser Imam November 6...

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