Chapter13Fall2005 - 1 Chapter 12 - The Citric Acid Cycle...

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1 Chapter 12 - The Citric Acid Cycle Summary : Yields reduced coenzymes (NADH and QH 2 ) and some ATP (2). Preparative step is oxidative decarboxylation involving coenzyme A. Occurs in eucaryotic mitochondrion and procaryotic cytosol. How does the pyruvate get into the mitochondrion from the cytosol? Pyruvate passes through channel proteins called  porins  (can transport  molecules < 10,000 daltons) located in outer mitochondrial membrane. To get from intermembrane space to matrix involves  pyruvate translocase   (symporter that also moves H +  into matrix). CONVERSION OF PYRUVATE TO ACETYL COA Enzyme is pyruvate dehydrogenase complex, composed of three enzymes: 1) pyruvate dehydrogenase 2) dihydrolipoamide acetyltransferase 3) dihydrolipoamide dehydrogenase Reaction occurs in 5 steps: 1) E 1  uses TPP as a prosthetic group and decarboxylates pyruvate --> forms  HETPP  intermediate 2) E 1  then transfers acetyl group to oxidized lipoamide --> acetyllipoamide 3) E 2  transfers acetyl group to coenzyme A to form acetyl CoA;  dihydrolipoamide becomes reduced 4) E 3  reoxidizes lipoamide portion of E 2 ; prosthetic group of E 3  (FAD)  oxidizes  reduced lipoamide --> FADH 2 5) NAD +  is reduced by E
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This note was uploaded on 08/02/2009 for the course BIOCHEMIST 100 taught by Professor Crew during the Spring '05 term at North Alabama.

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Chapter13Fall2005 - 1 Chapter 12 - The Citric Acid Cycle...

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