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Cellular Respiration Stage 1: Glycolysis AP Biology 2007-2008 What’s the point? The point is to make ATP! ATP AP Biology 2007-2008 Glycolysis Breaking down glucose “glyco – lysis” (splitting sugar) glucose pyruvate 2x 3C 6C In the cytosol? Why does that make evolutionary sense? inefficient generate only 2 ATP for every 1 glucose occurs in cytosol AP Biology That’s not enough ATP for me! Evolutionary perspective Prokaryotes are ancestors of all modern life no organelles (no mitochonria) Anaerobic atmosphere No free oxygen (O2) in atmosphere ALL cells still utilize glycolysis AP Biology Overview glucose C-C-C-C-C-C 10 reactions enzyme 2 ATP enzyme 2 ADP convert fructose-1,6bP glucose (6C) to P-C-C-C-C-C-C-P enzyme enzyme 2 pyruvate (3C) enzyme produces: 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 Biology G3P = glyceraldehyde-3-phosphate pyruvate C-C-C 2 NAD+ 2 4 ADP 4 ATP Glycolysis summary endergonic invest some ATP ENERGY INVESTMENT -2 ATP ENERGY PAYOFF G3P C-C-C-P 4 ATP NET YIELD AP Biology exergonic harvest a little ATP & a little NADH net yield 2 ATP 2 NADH http://www.youtube.com/watch?v=3GTj QTqUuOw&feature=related http://highered.mcgrawhill.com/sites/007352543x/student_view 0/chapter8/how_glycolysis_works.html AP Biology 1st half of glycolysis (5 reactions) Glucose “priming” get glucose ready to split phosphorylate CH2 O O P Glucose 6-phosphate 2 P O ADP CH2 O O P CH2 CH2 CH2OH O 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) H C O CHOH CH2 O NAD+ AP Biology O Fructose 6-phosphate 3 ATP phosphofructokinase split destabilized glucose P ADP phosphoglucose isomerase glucose molecular rearrangement CH2OH Glucose 1 ATP hexokinase O P O CHOH CH2 O P O P Important enzyme Phosphofructokinase (PFK) in step “3” of glycolysis (second ATP is used) (Allosteric enzyme) Activated by ADP (speeds respiration when ATP is needed) Inhibited by ATP (slows respiration when ATP is in excess) AP Biology 2nd half of glycolysis (5 reactions) DHAP P-C-C-C Energy Harvest NADH production G3P donates H NAD+ NADH ATP production G3P pyruvate PEP sugar donates P “substrate level phosphorylation” ADP ATP NAD+ Pi G3P C-C-C-P Pi 6 NAD+ NADH NADH 7 phosphoglycerate kinase ADP ATP 3-Phosphoglycerate (3PG) ADP ATP 3-Phosphoglycerate (3PG) 8 phosphoglyceromutase 2-Phosphoglycerate (2PG) Phosphoenolpyruvate (PEP) ADP H2O Phosphoenolpyruvate (PEP) 10 pyruvate kinase ADP C O H C O CH2OH Pyruvate C C O O CH2 OC ATP Pyruvate O P P O- ATP AP Biology CHOH CH2 O- 2-Phosphoglycerate (2PG) 9 enolase H2O OC O C O CH3 P Substrate-level Phosphorylation ATP is made directly from a “substrate” The Substrate is phosphorylated, oxidized and ATP is made from ADP The 4 ATP made in Glycolysis are made this way ATP 9 enolase H2O Phosphoenolpyruvate (PEP) ADP OH2O Phosphoenolpyruvate (PEP) 10 pyruvate kinase ATP ATP Pyruvate AP Biology I get it! The Pi came directly from the substrate! ADP Pyruvate C C CH2 O O OC O C O CH3 P Energy accounting of glycolysis 2 ATP 2 ADP glucose pyruvate 2x 3C 6C 4 ADP 4 ATP 2 NAD+ 2 But glucose has so much more to give! Net gain = 2 ATP + 2 NADH 1 6C sugar 2 3C sugars- (pyruvates) AP Biology Is that all there 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 Pyruvate is a branching point Pyruvate O2 O2 fermentation anaerobic respiration mitochondria Krebs cycle aerobic respiration AP Biology Lactic Acid Fermentation(anaerobic) C3H4O3 Pyruvate NADH C3H6O3 NAD+ Lactate Pyruvate is REDUCED to Lactate and NAD+ is regenerated so respiration can continue. This occurs in muscles in O2 debt (when running hard) until the debt is repaid (when you slow down) AP Biology There is no O2. Therefore pyruvate cannot be oxidized. Instead, it is reduced by NADH. No more ATP can be made AP Biology Alcohol Fermentation pyruvate ethanol + CO2 3C NADH 2C NAD+ Dead end process at ~12% ethanol, kills yeast AP Biology 1C bacteria yeast recycle NADH Lactic Acid Fermentation pyruvate lactic acid 3C NADH 3C NAD+ 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 Fermentation (anaerobic) Bacteria, yeast pyruvate ethanol + CO2 3C 2C NADH 1C NAD+ beer, wine, bread Pyruvate is reduced to ethanol Animals, some fungi pyruvate lactic acid 3C NADH 3C NAD+ anaerobic exercise (no O2) AP Biology Pyruvate is reduced to lactate