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AP Biology What’s the point? The p point is to make Cellular Respiration Stage 1: Glycolysis ATP! ATP AP Biology 2007-2008 AP Biology Glycolysis Evolutionary perspective Breaking down glucose Prokaryotes “glyco – lysis” (splitting sugar) glucose → → → → → pyruvate 2x 3C 6C transfer energy from organic molecules to ATP still is starting point for ALL cellular respiration occurs in cytosol That’s not enough ATP for me! life on Earth first evolved without free oxygen (O2) in atmosphere energy had to be captured from organic molecules in absence of O2 of all modern life ______________________________________ Enzymes of glycolysis are “well-conserved” Prokaryotes that evolved glycolysis are ancestors but it’s inefficient AP Biology first cells had no organelles Anaerobic atmosphere ancient pathway which harvests energy where energy transfer first evolved In the cytosol? Why does that make evolutionary sense? AP Biology ___________________________________________ You mean we’re related? Do I have to invite them over for the holidays? 1 AP Biology glucose C-C-C-C-C-C Overview Glycolysis summary enzyme 2 ATP enzyme 2 ADP 10 reactions convert fructose-1,6bP glucose (6C) to P-C-C-C-C-C-C-P enzyme enzyme 2 pyruvate (3C) enzyme DHAP G3P produces: _______________ P-C-C-C C-C-C-P 2H 2Pi enzyme consumes: _______________ enzyme net yield: 2Pi enzyme _______________ -2 ATP ENERGY PAYOFF get glucose ready to split phosphorylate glucose g AP Biology 2nd half of glycolysis (5 reactions) P CH2 O O P P CH2OH P O CH2 O CH2 Fructose 1,6-bisphosphate aldolase O CH2 4,5 isomerase O Dihydroxyacetone CH2OH phosphate NAD+ H Glyceraldehyde 3 -phosphate (G3P) Pi NAD+ Pi 6 glyceraldehyde NADH NADH 3-phosphate P dehydrogenase 1,3-Bisphosphoglycerate 1,3-Bisphosphoglycerate (BPG) (BPG) C O CHOH CH2 O O O NADH production Glucose 6-phosphate 2 CH2 O O P G3P donates H oxidizes the sugar reduces NAD+ __________________ NAD+ G3P → → → pyruvate PEP sugar donates P _________________ __________________ P AP Biology Payola! Finally some ATP! Pi 6 NAD+ NADH 7 phosphoglycerate kinase ADP ATP 3-Phosphoglycerate ((3PG)) ADP ATP 3-Phosphoglycerate ((3PG)) 8 phosphoglyceromutase 2-Phosphoglycerate (2PG) Phosphoenolpyruvate (PEP) ADP C O P O C H C O CH2OH P OH2O Phosphoenolpyruvate (PEP) 10 pyruvate kinase ADP Pyruvate C C O O P CH2 OC ATP ATP Pyruvate OCHOH CH2 O- 2-Phosphoglycerate (2PG) 9 enolase H2O _________________ P Pi G3P C-C-C-P NADH ATP production O CHOH CH2 O DHAP P-C-C-C Energy Harvest O Fructose 6-phosphate 3 phosphofructokinase C AP Biology CH2OH ADP ADP _________ _________ _________ NET YIELD 4 ATP ATP split destabilized glucose _______________ harvest a little ATP & a little NADH like $$ in the bank 4 ADP Glucose 1 ATP hexokinase phosphoglucose isomerase molecular rearrangement 4 ATP 2 1st half of glycolysis (5 reactions) Glucose “priming” G3P C-C-C-P C CCP 2 NAD+ pyruvate C-C-C DHAP = dihydroxyacetone phosphate AP Biology G3P = glyceraldehyde-3-phosphate _______________ invest some ATP ENERGY INVESTMENT O C O CH3 2 AP Biology Substrate-level Phosphorylation Energy accounting of glycolysis In the last steps of glycolysis, where did 2 ATP 2 ADP the P come from to make ATP? 9 the sugar substrateH O(PEP) enolase OH2O 2 P is transferred from PEP to ADP 9kinase enzyme 9ADP → ATP AP Biology Phosphoenolpyruvate (PEP) Phosphoenolpyruvate (PEP) 10 pyruvate kinase ADP ADP Pyruvate Pyruvate glucose → → → → → pyruvate 2x 3C 6C O C O CH2 P OC ATP ATP C O C O CH3 ATP O2 AP Biology O2 But glucose has so much more to give! some energy investment (-2 ATP) small energy return (4 ATP + 2 NADH) G3P DHAP NAD+ raw materials → products only l harvest h t 3.5% 3 5% off energy stored t d iin glucose l more carbons to strip off = more energy to harvest O2 2 But can’t stop there! for 1 billon years+ this is how life on Earth survived O2 2 NAD+ All that work! And that’s all I get? AP 1Biology 6C sugar → 2 3C sugars no O2= slow growth, slow reproduction O2 4 ATP Net gain = 2 ATP + 2 NADH I get it! The PO4 came directly from the substrate! Is that all there is? Not a lot of energy… 4 ADP glucose → → → → pyruvate 2x 3C 6C Hard way to make a living! Pi + NADH NAD Pi 1,3-BPG NADH NAD+ Going to run out of NAD+ 1,3-BPG NADH ADP ATP 3-Phosphoglycerate (3PG) 3-Phosphoglycerate (3PG) → 2 pyruvate + 2ATP + 2NADH 8 2-Phosphoglycerate (2PG) 2-Phosphoglycerate (2PG) 9 HO __________________________ __________________________ Phosphoenolpyruvate (PEP) another molecule must accept HADP 10 from NADH ATP so AP Biology + NADH NAD ATP Glycolysis NAD+ Pi 7 ADP glucose + 2ADP + 2Pi + 2 6 Pi 2 NAD+ is freed up for another round Pyruvate H2O Phosphoenolpyruvate (PEP) ADP ATP Pyruvate 3 AP Biology How is NADH recycled to NAD+? ___________________ ___________________ ___________________ ___________________ Another molecule ___________________ must accept H pyruvate from NADH H2O O2 pyruvate → ethanol + CO2 NAD+ NADH recycle NADH acetyl-CoA Fermentation (anaerobic) _____________________ CO2 3C acetaldehyde NAD+ beer, wine, bread 3C NADH 2C 1C bacteria yeast recycle NADH 3C AP Biology at ~12% ethanol, ethanol kills yeast can’t reverse the reaction cheese, anaerobic exercise (no O2) pyruvate → lactic acid 3C NADH O2 animals some fungi recycle 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 NAD+back to glycolysis→→ Lactic Acid Fermentation NAD+ back to glycolysis→→ Dead end process 3C NADH → pyruvate → ethanol + CO2 back to glycolysis→→ pyruvate → lactic acid ethanol ____________ ____________ Alcohol Fermentation 1C _____________________ NAD+ lactate Krebs cycle NAD+ NADH ____________ ____________ which path you use depends on AP Biology who you are… 2C NADH NADH Count the carbons! AP Biology 4 AP Biology Pyruvate is a branching point What’s the point? Pyruvate O2 O2 The p point is to make fermentation anaerobic respiration ATP! mitochondria Krebs cycle aerobic respiration ATP AP Biology AP Biology H+ And how do we do that? H H+ + H+ H+ H+ H+ H+ NO! There’s still more to my story! Any Questions? ATP synthase set up a H+ gradient allow H+ to flow tthrough oug ATP synthase sy t ase powers bonding of Pi to ADP ADP + P ADP + Pi → ATP ATP H+ AP Biology But… Have we done that yet? AP Biology 5
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