411U3 - Structure of ATP and NAD Purposes/Roles/Functions...

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Unformatted text preview: Structure of ATP and NAD Purposes/Roles/Functions of Glycolysis • 1. Produce ATP • 2. Feed ATP production via PDH, TCA, ET, OP • 3. Feed production of TCA intermediates • 4. Feed FA synthesis via PDH • 5. Feed AA synthesis via TCA intermediates Glycolysis Net Rxn (adding all rxns) • ATP + G G6P + ADP • G6P F6P • ATP + F6P F1,6BP + ADP • F1,6BP GAP + DHAP • DHAP GAP • 2Pi + 2NAD+ + 2GAP 2 (1,3BPG) + 2NADH • 2 (1,3BPG) + 2ADP 2 (3PG) + 2ATP • 2 (3PG) 2 (2PG) • 2 (2PG) 2 PEP • 2 PEP + 2 ADP 2pyr + 2ATP ___________________________________________ • G + 2Pi + 2 ADP + 2NAD+ 2pyr + 2 ATP + 2NADH Lactate Dehydrogenase (LDH) • Purpose of LDH: to covert the NADH produced in GAPDH back to NAD + for use in GAPDH. • This is required to keep glycolysis ( G’lys ) going rapidly during rapid muscle activity . • The sum: [NAD + ] + [NADH] is small. All of it would soon be converted to NADH if it was not recycled. LDH • In muscle, NADH is converted to NAD + via ET: 2NADH + 2H + + O 2---> 2H 2 O + 2NAD + ; • but in active muscle, NADH production exceeds the capacity to deliver O 2 to ET, so LDH also converts NADH to NAD + . • This removes the limitation that O 2 delivery rate would place on the maximum rate of muscle activity: we can sprint and go into O 2 debt rather than just jog. LDH • LDH rxn: • pyruvate + NADH + H + <-----> lactate + NAD + • In active muscle, the capacity to consume O 2 exceeds ability to deliver, so [O 2 ] decreases: anaerobic conditions. • But O 2 delivery by heart, lungs, and Hb is at the maximum possible rate and O 2 consumption in muscle is the highest ever: aerobic conditions . • Anaerobic G’lys produces 2 ATP per G converted to lactate at a high rate only when aerobic G’lys is rapid (and only in addition to aerobic G’lys) . A erobic glycolysis (working with PDH, TCA, ET, and OP) produces 36 or 38 ATP per G converted to carbon dioxide. Fates of Pyruvate • Depending on the organism in question and the conditions under which it is operating, pyruvate may be converted to: • Lactate • Acetyl coenzyme A (ACoA) • Ethanol • Oxaloacetate • Alanine Gluconeogenesis • Gluconeogenesis: in the liver , pyruvate (or oxaloacetate) is converted to G to increase [G] in the blood: • 1. in short-term CH 2 O starvation: muscle protein is hydrolysed to AAs which go to the blood and to the liver where they are converted to oxac G to supply G to the brain when [G] is low in the blood. • 2. in rapid muscle activity, lactate from muscles is converted back to G to go back to the muscles • Reactions: 7 of the reactions are the same reactions (same Es) as in glycolysis: they just go faster in reverse during gluconeogenesis (G’neo) . (Q becomes greater than K) • The irreversible reactions of glycolysis (G’lysis) are bypassed ( NOT reversed ) Net Reaction for G’neo • To bypass PK (twice/G) consumes 2ATP + 2GTP....
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This note was uploaded on 04/22/2011 for the course BIOCHEM 411 taught by Professor Thomas during the Spring '11 term at Tennessee Martin.

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411U3 - Structure of ATP and NAD Purposes/Roles/Functions...

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