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Cellular Respiration Harvesting Chemical Energy

Cellular Respiration Harvesting Chemical Energy. Tuesday, Nov. 12 th. Cellular Respiration Stage 1: Glycolysis. Today I will… Describe the process of glycolysis . State the reactants and products of glycolysis. Modified from Kim Foglia. What’s the point?. The Point is to Make ATP!. ATP.

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Cellular Respiration Harvesting Chemical Energy

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  1. Cellular RespirationHarvesting Chemical Energy

  2. Tuesday, Nov. 12th Cellular RespirationStage 1:Glycolysis Today I will… Describe the process of glycolysis. State the reactants and products of glycolysis. Modified from Kim Foglia

  3. What’s the point? The Point is to Make ATP! ATP

  4. glucose      pyruvate 6C 3C 2x Glycolysis • Breaking down glucose • “glyco – lysis” (splitting sugar) • most ancient form of energy capture • starting point for all cellular respiration • inefficient • generate only2 ATP for every 1 glucose • occurs in cytosol • why does that make evolutionary sense?

  5. Evolutionary perspective • Life on Earth first evolved withoutfree oxygen (O2) in atmosphere • energy had to be captured from organic molecules in absence of O2 • Prokaryotes that evolved glycolysis are ancestors of all modern life • ALL organisms still utilize glycolysis

  6. 2 ATP 2 ADP 2 NAD+ 2 Pi 2 NADH 4 ADP 4 ATP Overview glucose C-C-C-C-C-C activationenergy 10 reactions • convert 6C glucose to two 3C pyruvate • produce 2 ATP & 2 NADH fructose-6P P-C-C-C-C-C-C-P DHAP P-C-C-C G3P (PGAL) C-C-C-P The electron carrier NAD+ is a coenzyme pyruvate C-C-C G3P = glyceraldehyde-3-phosphate DHAP = dihydroxyacetone phosphate

  7. Glycolysis summary endergonic invest some ATP exergonic harvest a little ATP & a little NADH yield 2 ATP 2 NADH

  8. 1st half of glycolysis (5 reactions) • Glucose “priming” • get glucose ready to split • phosphorylate glucose • rearrangement • split destabilized glucose PGAL

  9. 2nd half of glycolysis (5 reactions) • Energy Harvest • NADH production • G3P donates H • oxidize sugar • reduce NAD+ • NAD+ NADH • ATP production • G3P  pyruvate • sugars donate P • ADP  ATP

  10. 2 ATP 2 ADP 4 ADP 4 ATP Energy accounting of glycolysis • Net gain = 2 ATP • some energy investment (-2 ATP) • small energy return (+4 ATP) • 1 6C sugar 2 3C sugars glucose      pyruvate 6C 3C 2x ATP

  11. O2 O2 O2 O2 O2 3C 2x Is that all there is? • Not a lot of energy… • for 1 billon years+ this is how life on Earth survived… Why? • slow growth, slow reproduction • only harvest 3.5% of energy stored in glucose • more carbons to strip off = more energy to harvest glucose     pyruvate 6C

  12. Glycolysis glucose + 2ADP + 2Pi + 2 NAD+ 2 pyruvate + 2ATP + 2NADH glucose + 2ADP + 2Pi + 2 NAD+ 2 pyruvate + 2ATP + 2NADH NADH We can’t stop there…. • Going to run out of NAD+ • without regenerating NAD+, energy production would stop • another molecule must accept H from NADH How is NADH recycled to NAD+?

  13. O2 O2 NADH How is NADH recycled to NAD+? • Another molecule must accept H from NADH • aerobic respiration • to Electron Transport Chain in mitochondria • anaerobic respiration • ethanol fermentation • lactic acid fermentation which path you use depends on who you are…

  14. pyruvate  ethanol + CO2 3C 2C 1C pyruvate  lactic acid NADH NADH NAD+ NAD+ 3C 3C Fermentation (anaerobic) • Bacteria, yeast to glycolysis • beer, wine, bread • Animals, some fungi to glycolysis • cheese, anaerobic exercise (no O2)

  15. pyruvate  ethanol + CO2 3C 2C 1C NADH NAD+ Alcohol Fermentation bacteria yeast • Dead end process • at ~12% ethanol, kills yeast • can’t reverse the reaction

  16. O2 pyruvate  lactic acid NADH NAD+ 3C 3C Lactic Acid Fermentation animals  • Reversible process • once O2 is available, lactate is converted to pyruvate by liver

  17. O2 O2 Pyruvate is a branching point Pyruvate fermentation Kreb’s cycle mitochondria

  18. What’s the point? The Point is to Make ATP! ATP

  19. H+ H+ H+ H+ H+ H+ H+ H+ ADP + Pi H+ And how do we do that? • Set up a H+ gradient • Allow the H+to flow through ATP synthase ADP + PiATP ATP Have we done that yet?

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