2. CELLULAR RESPIRATION Harvesting chemical energy ATP

3. HARVESTING STORED ENERGY Energy is stored in organic molecules Carbohydrates, fats, proteins Heterotrophs eat these organic molecules (food) Digest organic molecules to get … Raw materials for synthesis Fuels for energy Controlled release of energy “Burn” fuels in a series of step-by-step enzyme-controlled reactions

4. HARVESTING STORED ENERGY Example: glucose Catabolism of glucose to produce ATP C 6 H 12 O 6 6O 2 ATP6H 2 O6CO 2  + ++ CO 2 + H 2 O + heat fuel (carbohydrates) COMBUSTION = making a lot of heat energy by burning fuels in one step RESPIRATION = making ATP (& some heat) by burning fuels in many small steps CO 2 + H 2 O + ATP (+ heat) ATP glucose glucose + oxygen  energy + water + carbon dioxide respiration O2O2 O2O2 + heat enzymes ATP

5. HOW DO WE HARVEST ENERGY FROM FUELS? Digest large molecules into smaller ones Break bonds & move electrons from one molecule to another As electrons move they carry energy with them That energy becomes stored in another bond, released as heat, or used to make ATP e-e- ++ e-e- +– loses e-gains e-oxidizedreduced oxidationreduction redox e-e- LEO goes GER

6. HOW DO ELECTRONS MOVE IN BIOLOGY? Moving electrons in living systems Electrons cannot move alone in cells Electrons move as part of a H atom Moving electrons = moving H p e + H + H +– loses e-gains e-oxidizedreduced oxidationreduction C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP  +++ oxidation reduction H e-e-

7. COUPLING OXIDATION & REDUCTION REDOX reactions in respiration Release energy as organic molecules breakdown Break C-C bonds Strip off electrons from C-H bonds by removing H atoms C 6 H 12 O 6  CO 2 = oxidized Electrons attracted to more electronegative atoms In biology, the most electronegative atom? O 2  H 2 O = reduced Couple REDOX reactions & use the released energy to synthesize ATP O2O2 C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP  +++ oxidation reduction

8. OXIDATION & REDUCTION Oxidation Adding O Removing H Loss of electrons Releases energy Exergonic Reduction Removing O Adding H Gain of electrons Stores energy Endergonic C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP  +++ oxidation reduction

9. MOVING ELECTRONS IN RESPIRATION Electron carriers move electrons by shuttling H atoms around NAD +  NADH (reduced) FAD +2  FADH 2 (reduced) NAD H + H reduction NAD + nicotinamide Vitamin B3 niacin NADH H oxidation How efficient! Build once, use many ways

10. OVERVIEW OF CELLULAR RESPIRATION 4 stages Anaerobic respiration Glycolysis Respiration without O 2 In cytosol Aerobic respiration Respiration with O 2 In mitochondria Oxidation of pyruvate Krebs cycle Electron transport chain C 6 H 12 O 6 6O 2 ATP6H 2 O6CO 2  +++ (+ heat )

11. CELLULAR RESPIRATION Stage 1: Glycolysis

12. What’s the point? The point is to make ATP ! ATP

13. GLYCOLYSIS Breaking down of glucose Glyco – lysis (sugar splitting) 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 Inefficient Generates only 2 ATP for every 1 glucose Occurs in cytosol That’s not enough ATP for me! In the cytosol? Why does that make evolutionary sense? glucose      pyruvate 2x2x 6C3C

14. EVOLUTIONARY PERSPECTIVE Prokaryotes First cells had no organelles Anaerobic atmosphere Life on Earth first evolved without free oxygen (O 2 ) in the atmosphere Energy had to be captured from organic molecules in the absence of O 2 Prokaryotes that evolved glycolysis are ancestors of all modern life ALL cells still utilize glycolysis You mean we’re related? Do I have to invite them over for the holidays?

15. OVERVIEW 10 reactions Convert glucose (6C) to 2 pyruvate (3C) Produces: 4 ATP & 2 NADH Consumes: 2 ATP Net yield: 2 ATP & 2 NADH glucose C-C-C-C-C-C 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 ATP 2 ADP 2 4 NAD + 2 2Pi2Pi enzyme 2Pi2Pi 2H2H 2 DHAP = dihydroxyacetone phosphate G3P = glyceraldehyde-3-phosphate 4 ATP

16. GLYCOLYSIS SUMMARY endergonic invest some ATP exergonic harvest a little ATP & a little NADH net yield 2 ATP 2 NADH 4 ATP ENERGY INVESTMENT ENERGY PAYOFF G3P C-C-C-P NET YIELD like $$ in the bank -2 ATP

17. 1 ST 5 REACTIONS OF GLYCOLYSIS PiPi 3 6 4,5 ADP NAD + Glucose hexokinase phosphoglucose isomerase phosphofructokinase Glyceraldehyde 3 -phosphate (G3P) Dihydroxyacetone phosphate Glucose 6-phosphate Fructose 6-phosphate Fructose 1,6-bisphosphate isomerase glyceraldehyde 3-phosphate dehydrogenase aldolase 1,3-Bisphosphoglycerate (BPG) 1,3-Bisphosphoglycerate (BPG) 1 2 ATP ADP ATP NADH NAD + NADH PiPi CH 2 CO CH 2 OH PO CH 2 OP O CHOH C CH 2 OP O CHOH CH 2 OP O OP O P O H CH 2 OH O CH 2 P O O CH 2 OH P O Glucose “priming” Get glucose ready to split Phosphorylate glucose Molecular rearrangement Split destabilized glucose

18. 2 ND 5 REACTIONS OF GLYCOLYSIS Energy harvest NADH production G3P donates H Oxidizes sugar Reduces NAD + NAD +  NADH ATP production G3P   pyruvate PEP sugar donates P “substrate level phosphorylation” ADP  ATP 7 8 H2OH2O 9 10 ADP ATP 3-Phosphoglycerate (3PG) 3-Phosphoglycerate (3PG) 2-Phosphoglycerate (2PG) 2-Phosphoglycerate (2PG) Phosphoenolpyruvate (PEP) Phosphoenolpyruvate (PEP) Pyruvate phosphoglycerate kinase phosphoglycero- mutase enolase pyruvate kinase ADP ATP ADP ATP ADP ATP H2OH2O CH 2 OH CH 3 CH 2 O-O- O C PH CHOH O-O- O-O- O-O- C C C C C C P P O O O O O O CH 2 NAD + NADH NAD + NADH G3P C-C-C-P PiPi PiPi 6 DHAP P-C-C-C Payola! Finally some ATP!

19. ENERGY ACCOUNTING OF GLYCOLYSIS Net gain = 2 ATP + 2 NADH some energy investment (-2 ATP) Small energy return (+4 ATP) 1 6C sugar  2 3C sugars 2 ATP2 ADP 4 ADP glucose      pyruvate 2x2x 6C3C ATP 4 2 NAD + 2 All that work! And that’s all I get? But glucose has so much more to give!

20. IS THAT ALL THERE IS? Not a lot of energy … For 1 billion+ years this is how life on Earth survived No O 2 = slow growth, slow reproduction Only harvest 3.5% of energy stored in glucose More carbons to strip off = more energy to harvest Hard way to make a living! O2O2 O2O2 O2O2 O2O2 O2O2 glucose     pyruvate 6C 2x2x 3C

21. WHAT ABOUT NAD + ? 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 to gather more H and process going raw materials  products Glycolysis glucose + 2ADP + 2P i + 2 NAD +  2 pyruvate + 2ATP + 2NADH

22. HOW IS NADH RECYCLED? Another molecule must accept H from NADH NADH pyruvate acetyl-CoA lactate ethanol NAD + NADH NAD + NADH CO 2 acetaldehyde H2OH2O Krebs cycle O2O2 lactic acid fermentation with oxygen aerobic respiration without oxygen anaerobic respiration “fermentation” recycle NADH which path you use depends on who you are… alcohol fermentation

23. FERMENTATION (ANAEROBIC) Bacteria, yeast beer, wine, bread Animals, some fungi cheese, yogurt, anaerobic exercise 1C 3C2C pyruvate  ethanol + CO 2 NADHNAD + back to glycolysis  3C pyruvate  lactic acid NADHNAD + back to glycolysis 

24. ALCOHOL FERMENTATION Dead end process At ~12% ethanol, kills yeast Can’t reverse the reaction 1C 3C2C pyruvate  ethanol + CO 2 NADHNAD + back to glycolysis  recycle NADH bacteria yeast

25. LACTIC ACID FERMENTATION Reversible process Once O 2 is available, lactate is converted back to pyruvate by the liver 3C pyruvate  lactic acid NADHNAD + back to glycolysis  recycle NADH animals some fungi O2O2 

26. PYRUVATE IS A BRANCHING POINT Pyruvate O2O2 O2O2 mitochondria Krebs cycle aerobic respiration fermentation anaerobic respiration

27. There’s still more to my story! But any questions yet?