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- 1. Cellular Respiration Stage 1: Glycolysis APBiology 2007-2008
- 2. What’s the point? The point isto make ATP! ATP AP Biology 2007-2008
- 3. Glycolysis Breaking downglucose “glyco – lysis” (splitting sugar) glucose → → → → → pyruvate 2x 3C 6C In the cytosol? Why does that make evolutionary sense? ancient pathway which harvests energy 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 only 2 ATP for every 1 glucose occurs in cytosol AP Biology That’s not enough ATP for me!
- 4. Evolutionary perspective Prokaryotes firstcells had no organelles Enzymes of glycolysis are “well-conserved” Anaerobic atmosphere life on Earth first evolved without free 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 AP Biology ALL cells still utilize glycolysis You mean we’re related? Do I have to invite them over for the holidays?
- 5. Overview glucose C-C-C-C-C-C 10 reactions enzyme enzyme 2 ATP 2ADP convert fructose-1,6bP glucose (6C) to P-C-C-C-C-C-C-P enzyme enzyme 2 pyruvate (3C) enzyme produces: DHAP G3P 4 ATP & 2 NADH P-C-C-C C-C-C-P 2H consumes: 2Pi enzyme 2 ATP enzyme net yield: 2Pi enzyme 2 ATP & 2 NADH DHAP = dihydroxyacetone phosphate AP G3P Biology = glyceraldehyde-3-phosphate pyruvate C-C-C 2 NAD+ 2 4 ADP 4 ATP
- 6. Glycolysis summary endergonic invest someATP ENERGY INVESTMENT -2 ATP ENERGY PAYOFF G3P C-C-C-P 4 ATP exergonic harvest a little ATP & a little NADH like $$ in the bank NET YIELD AP Biology net yield 2 ATP 2 NADH
- 7. 1st half ofglycolysis (5 reactions) Glucose “priming” get glucose ready to split phosphorylate ADP P CH2 O O P O P CH2 CH2 O CH2OH Fructose 1,6-bisphosphate O CH2 C 4,5 aldolase isomerase O Dihydroxyacetone CH2OH phosphate Glyceraldehyde 3 -phosphate (G3P) Pi NAD+ Pi 6 glyceraldehyde NADH NADH 3-phosphate P dehydrogenase 1,3-Bisphosphoglycerate 1,3-Bisphosphoglycerate (BPG) (BPG) NAD+ AP Biology O CH2 O O Glucose 6-phosphate 2 Fructose 6-phosphate 3 ATP phosphofructokinase split destabilized glucose P ADP phosphoglucose isomerase glucose molecular rearrangement CH2OH Glucose 1 ATP hexokinase H C O CHOH CH2 O O P O CHOH CH2 O P O P
- 8. 2nd half ofglycolysis (5 reactions) DHAP P-C-C-C Energy Harvest NADH production G3P donates H oxidizes the sugar reduces NAD+ NAD+ → NADH Pi NAD+ phosphorylation” ADP → ATP AP Biology Payola! Finally some ATP! Pi 6 NAD+ NADH NADH 7 phosphoglycerate kinase ADP ATP 3-Phosphoglycerate (3PG) ADP ATP 3-Phosphoglycerate (3PG) 8 phosphoglyceromutase ATP production G3P → → → pyruvate PEP sugar donates P “substrate level G3P C-C-C-P 2-Phosphoglycerate (2PG) Phosphoenolpyruvate (PEP) ADP H2O Phosphoenolpyruvate (PEP) 10 pyruvate kinase ADP O P ATP Pyruvate C O H C O CH2OH P OC C CH2 O O OC ATP Pyruvate CHOH CH2 O- 2-Phosphoglycerate (2PG) 9 enolase H2O OC O C O CH3 P
- 9. Substrate-level Phosphorylation Inthe last steps of glycolysis, where did the P come from to make ATP? 9 the sugar substrate O (PEP) enolase H H2O 2 P is transferred from PEP to ADP kinase enzyme ADP → ATP AP Biology Phosphoenolpyruvate (PEP) ADP Phosphoenolpyruvate (PEP) 10 pyruvate kinase Pyruvate I get it! The Pi came directly from the substrate! Pyruvate C C CH2 O O OC ATP ATP ATP ADP O- O C O CH3 P
- 10. Energy accounting ofglycolysis 2 ATP 2 ADP glucose → → → → → pyruvate 2x 3C 6C 4 ADP 4 ATP 2 NAD+ 2 Net gain = 2 ATP + 2 NADH All that work! And that’s all I get? But glucose has so much more to give! some energy investment (-2 ATP) small energy return (4 ATP + 2 NADH) AP Biology 1 6C sugar → 2 3C sugars
- 11. Is that allthere is? Not a lot of energy… for 1 billon years+ this is how life on Earth survived no O2 = slow growth, slow reproduction only harvest 3.5% of energy stored in glucose more carbons to strip off = more energy to harvest O2 O2 O2 O2 AP Biology O2 glucose → → → → pyruvate 2x 3C 6C Hard way to make a living!
- 12. But can’t stopthere! G3P DHAP NAD+ raw materials → products NADH NAD+ NADH Pi 6 1,3-BPG NAD+ Pi NADH NAD+ 1,3-BPG NADH 7 ADP Glycolysis Pi Pi ADP ATP ATP 3-Phosphoglycerate (3PG) 3-Phosphoglycerate (3PG) 2-Phosphoglycerate (2PG) 2-Phosphoglycerate (2PG) glucose + 2ADP + 2Pi + 2 NAD+ → 2 pyruvate + 2ATP + 2NADH 8 Going to run out of NAD+ H2O 9 without regenerating NAD+, energy production would stop! Phosphoenolpyruvate (PEP) another molecule must accept HADP 10 from NADH ATP so AP Biology NAD+ is freed up for another round Pyruvate H2O Phosphoenolpyruvate (PEP) ADP ATP Pyruvate
- 13. How is NADHrecycled to NAD+? Another molecule must accept H from NADH H2O O2 recycle NADH with oxygen without oxygen aerobic respiration anaerobic respiration “fermentation” pyruvate NAD+ NADH acetyl-CoA CO2 NADH NAD+ lactate acetaldehyde NADH NAD+ lactic acid fermentation which path you use depends on AP Biology who you are… Krebs cycle ethanol alcohol fermentation
- 14. Fermentation (anaerobic) Bacteria,yeast pyruvate → ethanol + CO2 3C NADH 2C NAD+ beer, wine, bread 1C back to glycolysis→→ Animals, some fungi pyruvate → lactic acid 3C NADH AP Biology 3C + NADback to glycolysis→→ cheese, anaerobic exercise (no O2)
- 15. Alcohol Fermentation pyruvate →ethanol + CO2 3C NADH 2C NAD+ back to glycolysis→→ Dead end process at ~12% ethanol, kills yeast can’t reverse the reaction Count the carbons! AP Biology 1C bacteria yeast recycle NADH
- 16. Lactic Acid Fermentation pyruvate→ lactic acid → 3C NADH 3C NAD+ back to glycolysis→→ Reversible process once O2 is available, lactate is converted back to pyruvate by the liver Count the carbons! AP Biology O2 animals some fungi recycle NADH
- 17. Pyruvate is abranching point Pyruvate O2 O2 fermentation anaerobic respiration mitochondria Krebs cycle aerobic respiration AP Biology
- 18. What’s the point? The point isto make ATP! ATP AP Biology 2007-2008
- 19. H+ And how dowe do that? H + H+ H+ H+ H + H+ H+ ATP synthase set up a H+ gradient allow H+ to flow through ATP synthase powers bonding of Pi to ADP ADP + P ADP + Pi → ATP ATP H+ AP Biology But… Have we done that yet?
- 20. NO! There’s still more tomy story! Any Questions? AP Biology 2007-2008
Editor's Notes
- #4 Why does it make sense that this happens in the cytosol? Who evolved first?
- #5 The enzymes of glycolysis are very similar among all organisms. The genes that code for them are highly conserved. They are a good measure for evolutionary studies. Compare eukaryotes, bacteria & archaea using glycolysis enzymes. Bacteria = 3.5 billion years ago glycolysis in cytosol = doesn’t require a membrane-bound organelle O2 = 2.7 billion years ago photosynthetic bacteria / proto-blue-green algae Eukaryotes = 1.5 billion years ago membrane-bound organelles! Processes that all life/organisms share: Protein synthesis Glycolysis DNA replication
- #6 1st ATP used is like a match to light a fire… initiation energy / activation energy. Destabilizes glucose enough to split it in two
- #7 Glucose is a stable molecule it needs an activation energy to break it apart. phosphorylate it = Pi comes from ATP. make NADH & put it in the bank for later.
- #11 And that’s how life subsisted for a billion years. Until a certain bacteria ”learned” how to metabolize O2; which was previously a poison. But now pyruvate is not the end of the process Pyruvate still has a lot of energy in it that has not been captured. It still has 3 carbons bonded together! There is still energy stored in those bonds. It can still be oxidized further.
- #12 So why does glycolysis still take place?
- #15 Count the carbons!! Lactic acid is not a dead end like ethanol. Once you have O2 again, lactate is converted back to pyruvate by the liver and fed to the Kreb’s cycle.