341lecture28nov18sakai

341lecture28nov18sakai - Cell Biology 341 Weds., November...

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Cell Biology 341 Weds., November 18, 2009 Today: ATP is synthesized by chemiosmosis in the mitochondrion The energy released by electron transport drives formation of an electrochemical gradient of H + Last lecture: finished chapter 13 ER resident proteins are bound by the KDEL receptor in the Golgi, and returned to the ER in COPI vesicles The sorting signal for lysosomal proteins is mannose-6-phosphate, bound by the M-6-P receptor in the trans Golgi Receptor-mediated endocytosis: advantages are specificity and concentration of cargo The receptor releases the cargo due to the low pH of the endosome Began chapter 14: energy conversion in mitochondria Cells couple part of the energy released by oxidation of glucose to drive formation of high energy bonds in carrier molecules like ATP and NADH
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Glucose is oxidized in glycolysis and the Citric Acid Cycle (CAC) Oxidation: loss of electrons Reduction: acceptance of electrons In these pathways, glucose gives up 24 e - in 6 oxidation/reduction reactions, each of which occurs twice • Ultimately, the electrons are passed to O 2 in the mitochondrion, producing 12 H 2 O But first, the electrons are transferred to electron acceptors called activated carriers: NAD + = nicotinamide adenine dinucleotide (see fig. 2-60) FAD = flavin adenine dinucleotide (figure 2-83) Both of these accept two electrons at a time
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ATP is a carrier with high energy phosphoanhydride bonds ATP is not an electron carrier Figure 2-57 This G can be coupled to an energetically unfavorable reaction in a pathway Hydrolysis or transfer of the terminal phosphate to another molecule has a high negative G in the mitochondrion, oxidation of NADH drives the phosphorylation of ADP → ATP
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341lecture28nov18sakai - Cell Biology 341 Weds., November...

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