Cellresp.

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Cellresp.

  1. 1. From Snickers to ATP
  2. 2.  Review  ATP  Cellular Respiration ◦ Glycolysis ◦ Pyruvate oxidation ◦ Krebs cycle ◦ Electron Transport chain  Fermentation
  3. 3.  All of our energy comes from?  This energy is the form of?  Plants convert this energy to?  The energy is potential (stored) energy stored in?  The energy is released by?  Most living organisms require energy in the form of?
  4. 4.  Oxidation of sugars, primarily glucose.  Key chemical reactions = REDOX reactions, transfer of electrons and H+ from one substance to another.  Energy is harvested from electrons and used to produce ATP.  ATP is stored in small quantities in cells but is primarily produced on demand by cellular respiration.
  5. 5. ATP consists of three phosphate groups, ribose, and adenine. Phosphate groups Ribose Adenine
  6. 6.  ATP production: ADP + P → ATP; 2 types ◦ Substrate level phosphorylation ◦ Oxidative phosphorylation
  7. 7.  2 types of Cellular Respiration ◦ Aerobic - oxygen is used as the final electron acceptor. ◦ Anaerobic – final electron acceptor is an inorganic molecule; some bacteria and archaea.  Fermentation – is also an anaerobic process.
  8. 8.  Summary of aerobic respiration using glucose: C6H12O6 (glucose) + 6O2 → 6CO2 + 6H2O + energy (ATP)  4 Steps, fig 9.8:
  9. 9.  In the cytosol, 10 reactions, 3 stages, fig 9.13 ◦ Glucose (6 C) is primed, using 2 ATP’s, and converted to fructose 1,6 – bisphosphate. ◦ Fructose is split into two 3-C molecules, glyceraldehyde 3-phosphate (G3P) ◦ Energy extraction: electrons and H+ transferred to 2NAD+ and 4 ATPs produced. Final product – 2 pyruvate molecules (3 C).
  10. 10. Glycolysis begins with an energy- investment phase of 2 ATP All 10 reactions of glycolysis occur in cytosol GLYCOLYSIS What goes in: What comes out: Glucose Glucose- 6-phosphate Fructose- 6-phosphate Fructose- 1,6-bisphosphate
  11. 11. Pyruvate The “2” indicates that glucose has been split into two 3-carbon sugars During the energy payoff phase, 4 ATP are produced for a net gain of 2 ATP
  12. 12. Figure 9-7Figure 9-7 NAD+ Reduction Oxidation Oxidized Oxidized Nicotinamide Phosphate Ribose Phosphate Ribose Adenine Phosphate Phosphate Ribose Ribose Adenine Reduced Nicotinamide NADH (electron carrier) Reduced
  13. 13.  Summary: Glucose + 2 NAD+ + 4ADP → 2 pyruvate + 2 NADH + 4ATP.  Note: each G3P is oxidized to produce 1 NADH and 2 ATP by substrate level phosphoylation.  2 ATP are used to pay back 2 used at the beginning.  Net Production: Glucose + 2 NAD+ + 4ADP → 2 pyruvate + 2 NADH + **2ATP.
  14. 14. Fig 9.14. What inhibits glycolysis?Fig 9.14. What inhibits glycolysis?
  15. 15.  Takes place in the outer membrane of the mitochondria, fig 9.16 and 9.17.  Each pyruvate (3 C) is oxidized to an acetyl group (2 C).  Each acetyl group is combined with Coenzyme A (CoA) and feeds into the Kreb’s Cycle.  Summary: 2 Pyruvate + 2 CoA + 2 NAD+ → 2CO2 + 2acetyl CoA + 2NADH
  16. 16. Figure 9-17Figure 9-17
  17. 17.  Takes place in the matrix of the mitochondria, 9 reactions, 2 stages, fig 9.19. ◦ Priming:  Each acetyl CoA (2 C) combines with oxaloacetate (4 C) in Kreb’s cycle to form citrate (6 C).  CoA removed and recycled.
  18. 18.  2 stages cont’d ◦ Energy Extraction:  Oxidation reactions transfer electrons and H+ to NAD+ and FADH. Each acetyl group that enters produces 3 NADH and 2 FADH2.  ATP produced by substrate level phosphorylation. Each acetyl group produces 2 ATP.
  19. 19. Figure 9-19Figure 9-19 Oxaloacetate Malate Fumarate Succinate Succinyl CoA α-Ketoglutarate Citrate Isocitrate Pyruvate Acetyl CoA THE KREBS CYCLE In each turn of the cycle, the two blue carbons are converted to CO2 The two red carbons enter the cycle via acetyl CoA All 8 reactions of the Krebs cycle occur in the mitochondrial matrix, outside the cristae In the next cycle, this red carbon becomes a blue carbon
  20. 20.  Summary:  2 acetyl CoA + 2 oxaloacetate + 6NAD+ + 2FADH + 2ADP →  4CO2 + 6NADH + 2FADH2 + **2 ATP + 2 oxaloacetate (remains in Kreb’s Cycle).  Regulation, fig 9.20.
  21. 21. These steps are also regulated via feedback inhibition, by ATP and NADHThis step is regulated by ATP Oxaloacetate Acetyl CoA Citrate
  22. 22. Figure 9-21Figure 9-21
  23. 23.  So far we have 4ATP and a bunch of electrons (energy) and H+ carried by NADH and FADH2.  NADH and FADH2 transfer electrons to the transport chain (ETC) on the cristae of the mitochondria, fig 9.24.
  24. 24.  The ETC “harvests” the energy from the electrons as they pass down the chain.  The energy harvested from the electrons is used to “pump” H+ from the matrix to the intermembrane space of the mitochondria (energy is stored in the H+ ).  This produces a concentration gradient for H+ .
  25. 25. Occurs in the inner membrane of the mitochondrion
  26. 26.  H+ reenter the matrix through the enzyme, ATP synthase.  ATP synthase recovers the energy and produces ATP via oxidative phosphorylation.  Using the H+ gradient to produce ATP is called chemiosmosis.
  27. 27. Figure 9.25
  28. 28.  H+ transferred to O2 to produce H2O.  Summary: 10 NADH + 2 FADH2 + 3O2 → **26 ATP + 6H2O.  Add the 2 from glycolysis and 2 from the Kreb’s cycle brings the total to 30 ATPs produced from every glucose molecule.
  29. 29.  Fate of pyruvate in the absence of oxygen.  Allows for ATP production on a small scale by recycling NAD+ for glycolysis.  2 types:
  30. 30.  Lactic acid fermentation:  Ethanol fermentation:
  31. 31. Figure 9-27bFigure 9-27b Lactic acid fermentation occurs in humans. 2 Pyruvate 2 Lactate No intermediate; pyruvate accepts electrons from NADH
  32. 32. Figure 9-27cFigure 9-27c Alcohol fermentation occurs in yeast. 2 Pyruvate 2 Acetylaldehyde2 Ethanol
  33. 33.  Metabolism = all of the chemical reactions in an organism ◦ Catabolism ◦ Anabolism
  34. 34.  In the absence of available glucose, fats and proteins can feed into glycolysis and the Kreb’s Cycle, fig 9.29.  Products of glycolysis and the Kreb’s cycle can be used to produce RNA/DNA, proteins and fats, fig 9.30.
  35. 35. Figure 9.29
  36. 36. Figure 9.30

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