Cellular Respiration

1. Cellular Respiration Where did Bruce Lee get all that energy from? Chapter 3

2. What is it? O2 1 36 ATP glucose Cellular resp. • Cellular respiration • An aerobic process (requires oxygen) • Uses chemical energy from glucose to make ATP • Chemical energy is now stored in ATP for use throughout the body

3. Four Main Stages • Glycolysis • Anaerobic • In cytosol • breaks glucose (6C) into 2 pyruvate molecules (3C) • releases ATP • Transition reaction (oxidative decarboxylation) • Pyruvate converted to acetyl CoA releasing CO2 • Kreb’s Cycle • Within mitochondrial matrix • Oxidize each acetyl CoA to CO2 • Releases ATP and co-enzymes (NADH, FADH2) • Electron Transport Chain • Along the inner mitochondrial membrane • Uses high energy electrons from NADH and FADH2 to create an electrochemical proton (H+) gradient which powers ATP synthesis

4. Fermentation • When oxygen is NOT available, cells can metabolize pyruvate (derived from glucose) by the process of fermentation. Two Types (i) alcohol fermentation: pyruvate (3C) converted (reduced) to ethyl alcohol (2C) and CO2; occurs in yeast cells (ii) lactic acid fermentation: pyruvate(3C) converted (reduced) to lactic acid (3C) in muscle cells

5. Cellular Respiration H+ H+ O2 H2O Energy glucose CO2 General Formula glucose + O2 CO2 + H2O + energy This process begins with glucose. Once it enters a cell, the process of glycolysis begins immediately in the cytoplasm where enzymes are waiting.

6. Glycolysis (I) Overview • This is the investment period of glycolysis • ATP is USED in order to “activate” glucose • This is accomplish by an enzyme mediated process called: substrate level phosphorylation • Involving the transfer of a phosphate group

7. Numbering the Carbons of Glucose C C O • In order to keep track of how glucose is modified and rearranged during glycolysis we number each carbon C C C C 6 5 glucose 1 4 3 2

8. Glycolysis (I) glucose C C glucose glucose-6-phosphate fructose-6-phosphate fructose-1-6-bisphosphate 2 molecules of PGAL (glyceraldehyde-3-phosphate) C C O O C C C C C C C C P P P P P P P P C C O P P P P C C C C P C C O C C C C P C C P O C C C C P C C C C C C P

9. Glycolysis (I) glucose C C ATP glucose glucose-6-phosphate fructose-6-phosphate fructose-1-6-biphosphate 2 molecules of PGAL (glyceraldehyde-3-phosphate) C C O O C C C C activation ADP C C C C P isomerization P C C O C C ATP C C activation ADP P C C P O C C C C cleavage P C C C C C C P

10. Glycolysis (I) 1.Activation: Phosphate from ATP is added to glucose to form glucose-6-phosphate. [substrate-level phosphorylation] 2. Isomerization: Glucose-6-phosphate is rearranged to form fructose-6-phosphate. 3. Activation: A second phosphate from another ATP is added to form fructose-1,6-bisphosphate. [substrate-level phosphorylation] 4. Cleavage: The unstable fructose-1,6-bisphosphatesplits into phosphoglyceraldehyde (PGAL) and dihydroxyacetone phosphate (DHAP). Investment

11. Glycolysis (II) Overview • This is the pay-off period of glycolysis • ATP and NADH (a high energy molecule) are PRODUCED during glycolysis II • By the end of glycolysis II, glucose has been broken down from 6 carbons to a 3 carbon compound called Pyruvate (pyruvic acid)

12. Glycolysis (II) H H H H H2O H2O PGAL PGAP PGA PEP Pyruvate NAD NAD Pi Pi NADH NADH P P P P P P P P P P P P P P C C C C C C P P P P C C C C C C P P P P P P P P P P P P C C C C C C C C C P P P C C C C C C P P C C C C C C C C C P

13. Glycolysis (II) H H H H H2O H2O PGAL PGAP PGA PEP Pyruvate NADH activation / redox NADH P P C C C C C C P P P P C C C C C C P P ATP ATP dephosphorylation isomerization / dehydration P P C C C C C C C C C P ATP ATP dephosphorylation P P C C C C C C P P C C C C C C C C C P

14. Glycolysis (II) 5.Activation/Redox: Each molecule of PGAL is oxidized by NAD and gains a phosphate to form 1,3-bisphosphoglycerate (PGAP). 6. Phosphorylation: Each PGAP loses a phosphate to ADP resulting in 2 ATP and two 3-phosphoglycerate molecules (3-PGA).[substrate-level phosphorylation] 7. Isomerization: Both 3-PGA molecules are rearranged to form 2-phosphoglycerate (2-PGA). [note: the text does not distinguish between 3-PGA and 2-PGA, but refers to both as PGA] 8. Dehydration: Both 2-PGA molecules are oxidized to phosphoenolpyruvate (PEP) by the removal of water. 9.Phosphorylation: Each PEP molecule loses a phosphate to ADP resulting in 2 more ATP and 2 molecules of pyruvate. [substrate-level phosphorylation] Pay-off

15. The Result 1 3 5 2 ATP 6 2 NADH 9 (high energy molecule) Energy in Glycolysis • Used 2 ATP • Made 4 ATP Net Gain: 4ATP – 2ATP = And

16. Glycolysis: overall reaction O2 C6H12O6 + 2ADP + 2P + 2NAD+  2C3H4O3 + 2NADH + 2ATP glucose (6C) pyruvate (3C) Notice: There is no oxygen used in glycolysis. It is an anaerobic process

17. The Power House! nucleus mitochondria • In the cytosol, for each glucose molecule consumed, only 2 ATP were produced • This means that 34 more ATP are made in the mitochondria! • How do we get in there and what happens inside!? cytosol ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP ATP

18. Inside the Mitochondria

19. Inside the Mitochondria • outer membrane: contains transport protein porin, which affects permeability • inner membrane: contains the phospholipid cardiolipin that makes membrane impermeable to ions, a condition which is required for ATP production • intermembrane space: fluid-filled area containing enzymes and hydrogen ions • matrix: location of Kreb’s Cycle • cristae: folds of the inner membrane where ETC enzymes are found

20. Transition Reaction C – C – C pyruvate mitochondrion Intermembrane space • multi-enzyme pyruvate dehydrogenase complex

21. Transition Reaction C – C – C CO2 pyruvate mitochondrion Intermembrane space 1. Decarboxylation C – C

22. Transition Reaction mitochondrion Intermembrane space NAD+ NADH 2. Oxidation C – C C – C

23. Transition Reaction mitochondrion Intermembrane space C – C 3. Attachment CoA

24. Transition Reaction C – C CoA mitochondrion Intermembrane space Acetyl CoA 3. Attachment

25. Transition Reaction • Decarboxylation (-CO2) of pyruvate leaving a 2C molecule • Oxidation by NAD+ forming an acetate molecule. • Attachment of coenzyme A forming acetyl coA. Steps A and B together are referred to as oxidative decarboxylation

26. Transition Reaction 1 is released CO2 1 NADH is produced • In the transition reaction, for each molecule of pyruvate: and

27. Transition Reaction 1 2 is released are released CO2 CO2 1 2 and NADH NADH is produced and are prodcued • Remember: There are 2 pyruvates produced for each glucose. Therefore, for each glucose: X2

28. Krebs Cycle 1. Acetyl coA breaks into coenzyme A, which is recycled, and an acetyl group (2C) which joins to oxaloacetate (4C) forming citrate (6C). 2. Citrate (6C) converts to isocitrate (6C). 3. Isocitrate (6C) loses CO2 and is then oxidized by NAD forming alpha-ketoglutarate (5C). [oxidative decarboxylation] 4. Alpha-ketoglutarate (5C) is converted to succinyl-coA (4C) in 3 steps: (i) loss of CO2 (ii) oxidation by NAD+ (iii) attachment of coenzyme A

29. Krebs Cycle 5. Succinyl coA (4C) is converted to succinate (4C) in the following way: - coenzyme A breaks off and is recycled; phosphate attaches temporarily to succinate and is then transferred to GDP forming GTP; GTP transfers phosphate to ADP forming ATP (substrate level phosphorylation). 6. Succinate (4C) is oxidized by FAD to form fumarate (4C). 7. Water is added to fumarate (4C) to form malate (4C). 8. Malate (4C) is oxidized by NAD+ to form oxaloacetate, which is regenerated to begin the cycle again.

30. Krebs Cycle Transition reaction Krebs Cycle

31. Krebs Cycle 2 are released CO2 3 NADH 1 ATP 1 FADH2 • In the Krebs Cycle for each molecule of pyruvate: and are produced

32. Krebs Cycle 2 4 are released are released CO2 CO2 6 3 and NADH NADH 1 ATP and 1 FADH2 2 ATP 2 FADH2 are prodcued are produced • Remember: There are 2 pyruvates produced for each glucose. Therefore, for each glucose: X2

33. The Story So Far 1 glucose 2 6 C – C – C CO2 pyruvate Tracking carbon: (6C) (1C) (3C)

34. The Story So Far 4 2 2 ATP ATP ATP in cytosol 2 2 6 2 2 NADH NADH NADH FADH2 FADH2 10 NADH Tracking High Energy Molecules

35. Using the High Energy Molecules • NADH and FADH2 have gained high energy electrons • These electrons are donated to electron carrier proteins in the Electron Transport Chain (ETC). • The energy from these electrons is then used to pump protons (H+) into the intermembrane space of the mitchondria

36. Electron Transport Chain Electron Carriers: • 1. NADH reductase [protein] • 2. Coenzyme Q [non-protein] • 3. Cytochromeb1 c1 • 4. Cytochrome c • 5. Cytochromec oxidase C Cristae Q Cytochrome b1c1 Cytochrome c Cytochrome c oxidase NADH reductase Co-enzyme Q ATP Synthase not part of the ETC [protein]

37. Electron Transport Chain • To pass electrons along ETC, each carrier is reduced (gains electrons) then oxidized (donates electrons) • Curious? Where do these electrons come from?Electrons come from hydrogen atoms (H atoms separate into electrons and protons) C Cristae Q

38. Electron Transport Chain • NADH donates a pair of electrons to NADH reductase • electrons continue along ETC via sequential oxidations and reductions C Cristae Q NAD+ NADH

39. Electron Transport Chain • FADH2 donates a pair of electrons to coenzyme Q • electrons also continue along ETC C Cristae Q FADH2

40. Electron Transport Chain • FADH2 donates a pair of electrons to coenzyme Q • electrons also continue along ETC C Cristae Q

41. H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ For each NADH, 6 H+ are pumped across the mitochondrion inner membrane C Cristae Q NAD+ H+ H+ H+ H+ H+ H+ H+ NADH H+ H+ H+ H+ H+ H+

42. H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ O2 H+ H+ H2O H+ H+ For each NADH, 6 H+ are pumped across the mitochondrion inner membrane Oxygen is the final electron acceptor and is converted to H2O C Cristae Q H+ H+ H+ H+ H+ H+ H+ H+ H+ H+

43. H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ O2 H+ H+ H2O H+ H+ For each FADH2, 4 H+ are pumped across the mitochondrion inner membrane C Cristae Q H+ H+ H+ H+ H+ H+ FADH2 H+ H+ H+ H+

44. H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ High Proton Concentration H+ H+ Gradient The electrochemical proton gradient (sometimes referred to as the proton motive force) C Cristae Q H+ Low Proton Concentration H+ H+ H+ H+ H+

45. H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ • Using the energy stored in the proton gradient, ATP is generated using oxidative phosphorylation: formation of ATP coupled to oxygen consumption C Cristae Q ATP H+ H+ H+ H+ H+ H+ Using the electrochemial proton gradient to produce ATP from ADP is called chemiosmosis

46. H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ 6 Pumps H+ H+ H+ H+ H+ H+ H+ H+ 1 ATP is generated for each proton pair flowing through ATP synthase. C Cristae Q ATP ATP ATP H+ H+ H+ H+ H+ H+ 3 NADH

47. H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ 4 Pumps H+ H+ H+ H+ H+ H+ H+ H+ 1 ATP is generated for each proton pair flowing through ATP synthase. C Cristae Q ATP ATP H+ H+ H+ H+ H+ H+ 2 FADH2

48. ATP synthase works a bit like a water mill

49. H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ The WHOLE process… C Cristae Q H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+

50. H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ The WHOLE process… C Cristae Q NAD+ H+ H+ H+ H+ H+ H+ H+ NADH H+ H+ H+ H+ H+ H+