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Glycolysis

Glycolysis. . C 6 H 12 O 6. +. 6O 2. ATP. +. 6H 2 O. +. 6CO 2. Overview of cellular respiration. 4 metabolic stages Anaerobic respiration 1. Glycolysis respiration without O 2 in cytosol Aerobic respiration respiration using O 2 in mitochondria 2. Pyruvate oxidation

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Glycolysis

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  1. Glycolysis

  2. C6H12O6 + 6O2 ATP + 6H2O + 6CO2 Overview of cellular respiration • 4 metabolic stages • Anaerobic respiration 1. Glycolysis • respiration without O2 • in cytosol • Aerobic respiration • respiration using O2 • in mitochondria 2. Pyruvate oxidation 3. Krebs cycle 4. Electron transport chain (+ heat)

  3. glucose      pyruvate 6C 3C 2x Glycolysis • Breaking down glucose • “glyco – lysis” (splitting sugar) • ancient • where energy transfer first evolved • transfer energy from organic molecules to ATP • still is starting point for ALL cellular respiration • but it’s inefficient • generate only2 ATP for every 1 glucose • occurs in cytosol

  4. enzyme enzyme enzyme enzyme enzyme enzyme enzyme enzyme ATP ATP 4 2 4 2 2 ADP NAD+ ADP 2Pi 2 2H 2Pi Overview glucose C-C-C-C-C-C 10 reactions • convert glucose (6C)to 2 pyruvate (3C) • produces:4 ATP & 2 NADH • consumes:2 ATP • net yield:2 ATP & 2 NADH fructose-1,6bP P-C-C-C-C-C-C-P DHAP P-C-C-C G3P C-C-C-P pyruvate C-C-C DHAP = dihydroxyacetone phosphate G3P = glyceraldehyde-3-phosphate

  5. Glycolysis summary endergonic invest some ATP ENERGY INVESTMENT -2 ATP G3P C-C-C-P exergonic harvest a little ATP & a little NADH ENERGY PAYOFF 4 ATP • net yield • 2 ATP • 2 NADH NET YIELD

  6. 1st half of glycolysis (5 reactions) CH2OH Glucose “priming” O Glucose 1 ATP hexokinase • get glucose ready to split • phosphorylate glucose (hexokinase) • molecular rearrangement • split destabilized glucose (1 DHAP, 1 G3P) ADP CH2 O P O Glucose 6-phosphate 2 phosphoglucose isomerase CH2 P O CH2OH O Fructose 6-phosphate 3 ATP phosphofructokinase P O CH2 CH2 O P O ADP Fructose 1,6-bisphosphate aldolase 4,5 H O CH2 P isomerase C O C O Dihydroxyacetone phosphate Glyceraldehyde 3 -phosphate (G3P) CHOH CH2OH CH2 O P NAD+ Pi NAD+ Pi 6 glyceraldehyde 3-phosphate dehydrogenase NADH NADH P O O CHOH 1,3-Bisphosphoglycerate (BPG) 1,3-Bisphosphoglycerate (BPG) CH2 O P

  7. 2nd half of glycolysis (5 reactions) DHAP P-C-C-C G3P C-C-C-P Energy Harvest • NADH production • G3P donates H • oxidizes the sugar • reduces NAD+ • NAD+ NADH • ATP production • G3P    pyruvate • PEP sugar donates P • “substrate level phosphorylation” • ADP  ATP Pi Pi NAD+ NAD+ 6 NADH NADH 7 ADP ADP O- phosphoglycerate kinase C ATP ATP CHOH 3-Phosphoglycerate (3PG) 3-Phosphoglycerate (3PG) CH2 P O 8 O- phosphoglycero-mutase O C H C O P 2-Phosphoglycerate (2PG) 2-Phosphoglycerate (2PG) CH2OH O- 9 H2O H2O enolase C O O C P Phosphoenolpyruvate (PEP) Phosphoenolpyruvate (PEP) CH2 O- 10 ADP ADP C O pyruvate kinase Payola!Finally some ATP! ATP ATP C O CH3 Pyruvate Pyruvate

  8. O- 9 H2O H2O enolase C O O C P Phosphoenolpyruvate (PEP) Phosphoenolpyruvate (PEP) CH2 O- 10 ADP ADP C O pyruvate kinase ATP ATP C O CH3 Pyruvate Pyruvate Substrate-level Phosphorylation • In the last steps of glycolysis, where did the P come from to make ATP? • the sugar substrate (PEP) • P is transferred from PEP to ADP • kinase enzyme • ADP  ATP ATP I get it! The Pi camedirectly fromthe substrate!

  9. DHAP G3P NAD+ Pi NAD+ Pi NADH NADH 1,3-BPG 1,3-BPG Pi Pi NAD+ NAD+ 6 NADH NADH 7 ADP ADP ATP ATP 3-Phosphoglycerate (3PG) 3-Phosphoglycerate (3PG) 8 2-Phosphoglycerate (2PG) 2-Phosphoglycerate (2PG) 9 H2O H2O Phosphoenolpyruvate (PEP) Phosphoenolpyruvate (PEP) 10 ADP ADP ATP ATP Pyruvate Pyruvate But can’t stop there! raw materialsproducts • Going to run out of NAD+ • without regenerating NAD+,energy production would stop! • another molecule must accept H from NADH • so NAD+ is freed up for another round Glycolysis glucose + 2ADP + 2Pi + 2 NAD+2pyruvate+2ATP+2NADH

  10. recycleNADH How is NADH recycled to NAD+? without oxygen anaerobic respiration “fermentation” with oxygen aerobic respiration Another molecule must accept H from NADH pyruvate NAD+ H2O CO2 NADH NADH O2 acetaldehyde NADH acetyl-CoA NAD+ NAD+ lactate lactic acidfermentation Krebs cycle ethanol alcoholfermentation

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