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Chapter 8 Powerpoint Le

  1. 1. Chapter 08 Cellular Respiratio
  2. 2. 2 Cellular Respiration Outline Glycolysis Transition Reaction Citric Acid Cycle Electron Transport System Fermentation Metabolic Pool Catabolism Anabolism
  3. 3. 3 Cellular Respiration Cellular Respiration A cellular process that requires oxygen and gives off carbon dioxide Usually involves breakdown of glucose to carbon dioxide and water Energy extracted from glucose molecule: ­ Released step-wise ­ Allows ATP to be produced efficiently Oxidation-reduction enzymes include NAD+ and FAD as coenzymes
  4. 4. Glucose 4 Breakdown: Summary Reaction
  5. 5. 5 Cellular Respiration NAD+ and FAD NAD+ (nicotinamide adenine dinucleotide) Called a coenzyme of oxidation-reduction it can ­ Oxidize a metabolite by accepting electrons ­ Reduce a metabolite by giving up electrons Each NAD+ molecule used over and over again FAD (flavin adenine dinucleotide) Also a coenzyme of oxidation-reduction Sometimes used instead of NAD+ Accepts two electrons and two hydrogen ions (H+) to become FADH2
  6. 6. NAD+ Cycle 6
  7. 7. Cellular Respiration: 7 Cellular Respiration Overview of 4 Phases Glycolysis:  Occurs in cytoplasm  Glucose broken down to two molecules of pyruvate  ATP is formed Transition reaction:  Both pyruvates are oxidized  Electron energy is stored in NADH  Two carbons are released as CO2 Citric acid cycle:  Electron energy is stored in NADH and FADH2  ATP is formed  Four carbons are released as CO2 Electron transport chain:  Extracts energy from NADH & FADH2  Produces 32 or 34 molecules of ATP
  8. 8. Glucose Breakdown: 8 Overview of 4 Phases
  9. 9. Glucose Breakdown: 9 Cellular Respiration Glycolysis Occurs in cytoplasm outside mitochondria Energy Investment Steps: Two ATP are used to activate glucose Glucose splits into two G3P molecules Energy Harvesting Steps: Two electrons (as hydrogen atoms) are picked up by two NAD+ Four ATP produced by substrate-level phosphorylation Net gain of two ATP Both G3Ps converted to pyruvates
  10. 10. Glycolysis: 10 The Balance Sheet
  11. 11. Substrate-level 11 Phosphorylation
  12. 12. Glycolysi 12 s
  13. 13. Glycolysi 13 s
  14. 14. Glucose Breakdown: 14 Cellular Respiration The Preparatory (Prep) Reaction End product of glycolysis, pyruvate, enters the mitochondrial matrix Pyruvate converted to 2-carbon acetyl group Attached to Coenzyme A to form acetyl-CoA Electron picked up (as hydrogen atom) by NAD+ CO2 released, and transported out of mitochondria into the cytoplasm
  15. 15. Mitochondrion: 15 Structure & Function
  16. 16. Preparatory 16 Reaction
  17. 17. Glucose Breakdown: 17 Cellular Respiration The Citric Acid Cycle A.K.A. Krebs cycle Occurs in matrix of mitochondria Both acetyl (C2) groups received from the preparatory reaction:  Join with an enzyme CoA molecule to make acetyl- CoA  Acetyl (C2) group transferred to oxaloacetate (C2) to make citrate (C6)  Each acetyl oxidized to two CO2 molecules  Remaining 4 carbons from oxaloacetate converted back to oxaloacetate (thus “cyclic”) NADH, FADH2 capture energy rich electrons ATP formed by substrate-level phosphorylation
  18. 18. The Citric Acid Cycle 18
  19. 19. Citric Acid Cycle: 19 Balance Sheet
  20. 20. 20 Cellular Respiration Electron Transport Chain Location: Eukaryotes: cristae of the mitochondria Aerobic Prokaryotes: plasma membrane Series of carrier molecules: Pass energy rich electrons along Complex arrays of protein and cytochromes ­ Cytochromes are respiratory molecules ­ Complex carbon rings with metal atoms in center Receives electrons from NADH & FADH2 Produce ATP by oxidative phosphorylation
  21. 21. 21 Cellular Respiration Electron Transport Chain The fate of the hydrogens: Hydrogens from NADH deliver enough energy to make 3 ATPs Those from FADH2 have only enough for 2 ATPs “Spent” hydrogens combine with oxygen Recycling of coenzymes increases efficiency Once NADH delivers hydrogens, it returns (as NAD+) to pick up more hydrogens However, hydrogens must be combined with oxygen to make water If O2 not present, NADH cannot release H No longer recycled back to NAD+
  22. 22. Electron Transport Chain 22
  23. 23. Organization of 23 Cristae
  24. 24. Glucose Catabolism: 24 Cellular Respiration Overall Energy Yield Net yield per glucose: From glycolysis – 2 ATP From citric acid cycle – 2 ATP From electron transport chain – 32 ATP Energy content: Reactant (glucose) 686 kcal Energy yield (36 ATP) 263 kcal Efficiency 39%; balance is waste heat
  25. 25. Overall Energy Yielded 25 per Glucose Molecule
  26. 26. 26 Cellular Respiration Fermentation (1) When oxygen limited: Spent hydrogens have no acceptor NADH can’t recycle back to NAD+ Glycolysis stops because NAD+ required Fermentation: “Anaerobic” pathway Can provide rapid burst of ATP Provides NAD+ for glycolysis NADH combines with pyruvate to yield NAD+
  27. 27. Fermentatio 27 n
  28. 28. 28 Cellular Respiration Fermentation (2) Pyruvate reduced by NADH to: Lactate ­ Animals & some bacteria ­ Cheese & yogurt; sauerkraut Ethanol & carbon dioxide ­ Yeasts ­ Bread and alcoholic beverages Allows glycolysis to proceed faster than O2 can be obtained Anaerobic exercise Lactic acid accumulates Causes cramping and oxygen debt When O2 restored, lactate broken down to acetyl-CoA and metabolized
  29. 29. Products of 29 Fermentation
  30. 30. Efficiency of 30 Fermentation InLine Figure 143
  31. 31. Metabolic Pool: 31 Cellular Respiration Catabolism (1) Foods: Sources of energy rich molecules Carbohydrates, fats, and proteins Catabolism (breakdown side of metabolism) Breakdown products enter into respiratory pathways as intermediates Carbohydrates ­ Converted into glucose ­ Processed as above
  32. 32. The Metabolic Pool 32 Concept
  33. 33. Metabolic Pool: 33 Cellular Respiration Catabolism (2) Breakdown products enter into respiratory pathways as intermediates (cont.) Proteins ­ Broken into amino acids (AAs) ­ Some AAs used to make other proteins ­ Excess AAs deaminated (NH2 removed) in liver  Results in poisonous ammonia (NH3)  Quickly converted to urea ­ Different R-groups from AAs processed differently ­ Fragments enter respiratory pathways at many different points
  34. 34. Metabolic Pool: 34 Cellular Respiration Anabolism (1) All metabolic reactions part of metabolic pool Intermediates from respiratory pathways can be used for anabolism Anabolism (build-up side of metabolism):  Carbs: ­ Start with acetyl-CoA ­ Basically reverses glycolysis (but different pathway)  Fats ­ G3P converted to glycerol ­ Acetyls connected in pairs to form fatty acids ­ Note – dietary carbohydrate RARELY converted to fat in humans!
  35. 35. Metabolic Pool: 35 Cellular Respiration Anabolism (2) Anabolism (cont.): Proteins: ­ Made up of combinations of 20 different amino acids ­ Some amino acids (11) can be synthesized from respiratory intermediates  organic acids in citric acid cycle can make amino acids  Add NH2 – transamination ­ However, other amino acids (9) cannot be synthesized by humans  Essentialamino acids  Must be present in diet or die
  36. 36. 36 Cellular Respiration Review Glycolysis Transition Reaction Citric Acid Cycle Electron Transport System Fermentation Metabolic Pool Catabolism Anabolism
  37. 37. Ending Slide Chapter 08 Cellular Respiratio