lecture2 - Lecture 2 Outline Glycolysis continued: Payoff...

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Unformatted text preview: Lecture 2 Outline Glycolysis continued: Payoff phase Pyruvate dehydrogenase (PDH) complex - page 12-16 Pyruvate dehydrogenase (E1) Dihydrolipoyl transacetylase (E2) Dihydrolipoyl dehydrogenase (E3) Co-factors of PDH complex thiamine pyrophosphate (TPP) - thiamine - E1 lipoic acid (E2) CoA - pantothenic acid (E2) FAD - riboflavin (E3) NAD - niacin (E3) Preparatory Phase Glucose + ATP Glucose-6-P + ADP Fructose-6-P Fructose-1,6-bisphosphate hexokinase phosphoglucoisomerase Phosphofructokinase 1 Glyceraldehyde -3-phosphate Dihydroxyacetone-P aldolase triose phosphate isomerase BIS 103 - Glycolysis Payoff Phase ATP hexokinase phosphoglucoisomerase Phosphofructokinase 1 aldolase triose phosphate isomerase BIS 103 - Glycolysis - End of Preparatory Phase At the end of the “preparatory phase”: 1. The glucose molecule has been cleaved to form 2 molecules of glyceraldehyde-3-P. 2. Two molecules of ATP have been expended during this phase. 3. Five enzymes have carried out these steps. Five more steps are required during the “payoff phase” to convert 2 mols of glyceraldehyde-3-P to 2 moles of pyruvate. During the “payoff phase” 4 mols of ATPs and 2 mols of NADH are produced. Thus, under “anaerobic” conditions there is a net synthesis of 2 mols of ATPs. 2 glyceraldehyde -3-phosphate 2 1,3 bisphosphoglyceric acid + 2 NADH + 2 H + 2 3-phosphoglyceric acid + 2 ATP glyceraldehyde-3-P dehydrogenase + 2 NAD + + 2 Pi +2 ADP phosphoglycerate kinase 2 2-phosphoglyceric acid phosphoglyceromutase 2 phosphoenolpyruvate (PEP) + 2 H 2 O enolase 2 pyruvic acid + 2 ATP pyruvate kinase Net gain in energy during glycolysis = 2 ATPs BIS 103 - Glycolysis - Payoff Phase-- In the first step of the payoff phase, G-3-P is oxidized to 1,3-bisPGA with the production of NADH + H + : BIS 103 Glycolysis - Payoff phase - step 1 glyceraldehyde-3-P dehydrogenase NAD + Pi NADH + H + ∆ G’ o = 6.3 kJ/mol 1,3-phosphoglycerate (1,3-bisPGA) CH 2 OP HC-OH O C-O-P CH 2 OP HC-OH O C H glyceraldehyde-3-P (G-3-P) NAD + accepts a hydride ion (:H + ) and is reduced to NADH + H + . The aldehyde group of G-3-P is dehydrogenated to a carboxylic acid anhydride with phosphoric acid. This acyl phosphate anhydride has a very high standard free energy of hydrolysis of -49.3 kJ/mol. This steps helps the aldolase step by removing one of its products and drives the aldolase reaction to the right. Much of the free energy of oxidation of the aldehyde group is conserved by the formation of the acyl phosphate group at C-1 of bisphosphoglycerate. The acceptor of hydrogen in this dehydrogenase reaction is NAD + , the oxidized form of nicotinamide adenine dinucletotide. This co-factor is derived from the vitamin niacin which provides the nicotinamide moiety....
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This note was uploaded on 04/19/2008 for the course BIS 103 taught by Professor Abel during the Spring '08 term at UC Davis.

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lecture2 - Lecture 2 Outline Glycolysis continued: Payoff...

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