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ch369_ch16-metabolism regulation

ch369_ch16-metabolism regulation - Chapter 16 Regulation of...

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Chapter 16 Regulation of Metabolism
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Why is it necessary to regulate metabolism? Need appropriate metabolism for the current energy state. (i.e., after eating too much sugar, you should be synthesizing lipids!) Metabolism needs to be coordinated between different organs & tissues & different cellular compartents. How do cells in different parts of the body coordinate their responses to a stimulus such as glucose availability?
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Hormones coordinate metabolic function. Hormones are substances produced by one tissue that influence function of other tissues. Today: Look at a few hormones involved in regulating metabolism: insulin, glucagon, epinephrin.
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How can an extracellular hormone influence intracellular function without actually entering a cell? Through the use of “ signal transduction pathways ”. Signal transduction: Process by which an extracellular signal (such as a hormone) communicates with the cellular interior. In a typical signal transduction pathway: Hormone binding to extracellular receptor causes ==> activation of intracellular kinase or phosphatase, causes ==> phosphorylation or dephosphorylation of target proteins ==> causes changes in activity of target proteins.
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In a typical signal transduction pathway: Hormone binds to extracellular receptor causing ==> activation of intracellular kinase or phosphatase, causing ==> phosphorylation or dephosphorylation of target proteins ==> which causes changes in activity of target proteins.
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Protein kinase substrates are typically Tyrosine, Serine, Threonine. Phosphorylation is a type of allosteric regulation. Proteins are phosphorylated by enzymes called “ kinases ”, phosphate is removed by “ phosphatase ” enzymes.
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Major Hormones Involved in Metabolism • Insulin • Glucagon Epinephrine (adrenalin) Each of these hormones provides an example of a signal transduction pathway. Look at insulin example first.
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Figure 16.05 Structure of human insulin. Insulin Insulin is a peptide hormone produced in pancreatic islet cells. Figure 16.06 Pancreatic islet cells.
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Production & Activation of Insulin
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Stimulates cells to take up glucose Suppresses glycogen breakdown when blood glucose levels are high Suppresses fatty acid release from adipose cells Stimulates triacylglycerol synthesis Effects of Insulin Summary: Insulin release indicates plenty of glucose is available for metabolism and storage.
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How does insulin cause these intracellular responses?
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Insulin is produced in pancrease, travels through blood, and binds to a specific receptor on cell surfaces.
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