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Cell respiration-apbio-1204285933555932-5



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  • FIGURE 8-1 A summary of glucose metabolism
  • Figure: 19-2 part a Title: Viral structure and replication part a Caption: (a) A cross section of the virus that causes AIDS. Inside, genetic material is surrounded by a protein coat and molecules of reverse transcriptase, an enzyme that catalyzes the transcription of DNA from the viral RNA template after the virus enters the host cell. This virus is among those that also have an outer envelope that is formed from the host cell's plasma membrane. Spikes made of glycoprotein (protein and carbohydrate) project from the envelope and help the virus attach to its host cell.


  • 1. Chapter 8Harvesting Energy
  • 2. Chapter 8 2 Overview of Glucose BreakdownThe overall equation for the complete breakdown of glucose is: C6H12O6 + 6O2  6CO2 + 6H2O + ATPThe main stages of glucose metabolism are: • Glycolysis • Cellular respiration
  • 3. Chapter 8 3
  • 4. Chapter 8 4 Overview of Glucose BreakdownGlycolysis • Occurs in the cytosol • Does not require oxygen • Breaks glucose into pyruvate • Yields two molecules of ATP per molecule of glucose
  • 5. Chapter 8 5 Overview of Glucose BreakdownIf oxygen is absent fermentation occurs • pyruvate is converted into either lactate, or into ethanol and CO2If oxygen is present cellular respiration occurs…
  • 6. Chapter 8 6 Overview of Glucose BreakdownCellular respiration • Occurs in mitochondria (in eukaryotes) • Requires oxygen • Breaks down pyruvate into carbon dioxide and water • Produces an additional 32 or 34 ATP molecules, depending on the cell type
  • 7. Chapter 8 7 GlycolysisOverview of the two major phases of glycolysis• Glucose activation phase• Energy harvesting phase
  • 8. Chapter 8 8 GlycolysisGlucose activation phase • Glucose molecule converted to highly reactive fructose bisphosphate by two enzyme-catalyzed reactions, using 2 ATPs
  • 9. Chapter 8 9 Essentials of Glycolysis (a) ATP ADP Glucose-6- Glucose P PhosphateC C C C C C C C C C C C Glucose-6- Fructose-1,6-P Phosphate P BisphosphateC C C C C C C C C C C C P ATP ADP
  • 10. Chapter 8 10 GlycolysisEnergy harvesting phase • Fructose bisphosphate is split into two three-carbon molecules of glyceraldehyde 3-phosphate (G3P) • In a series of reactions, each G3P molecule is converted into a pyruvate, generating two ATPs per conversion, for a total of four ATPs • Because two ATPs were used to activate the glucose molecule there is a net gain of two ATPs per glucose molecule
  • 11. Chapter 8 11Essentials of Glycolysis (b) Fructose-1,6- P Bisphosphate C C C C C C P P C C C C C C P C C C G3P C C C P P
  • 12. Chapter 8 12 GlycolysisEnergy harvesting phase (continued) • As each G3P is converted to pyruvate, two high-energy electrons and a hydrogen ion are added to an “empty” electron-carrier NAD+ to make the high- energy electron-carrier molecule NADH • Because two G3P molecules are produced per glucose molecule, two NADH carrier molecules are formed
  • 13. Chapter 8 13 Essentials of Glycolysis (c) C C C G3P C C CPi Pi P P NAD+ NAD+ NADH NADH C C C C C C ADP P P P P ADP ADP ADP ATP ATP ATP C C C Pyruvates C C C ATP
  • 14. Chapter 8 14 GlycolysisSummary of glycolysis: • Each molecule of glucose is broken down to two molecules of pyruvate • A net of two ATP molecules and two NADH (high-energy electron carriers) are formed
  • 15. Chapter 8 15Fermentation of Dough
  • 16. Chapter 8 16 FermentationPyruvate is processed differently under aerobic and anaerobic conditionsUnder aerobic conditions, the high energy electrons in NADH produced in glycolysis are ferried to ATP- generating reactions in the mitochondria, making NAD+ available to recycle in glycolysis
  • 17. Chapter 8 17 FermentationUnder anaerobic conditions, pyruvate is converted into lactate or ethanol, a process called fermentationFermentation does not produce more ATP, but is necessary to regenerate the high-energy electron carrier molecule NAD+, which must be available for glycolysis to continue
  • 18. Chapter 8 18 FermentationSome microbes ferment pyruvate to other acids (as seen in making of cheese, yogurt, sour cream)Some microbes perform fermentation exclusively (instead of aerobic respiration)Yeast cells perform alcoholic fermentation
  • 19. Chapter 8 19 Alcoholic Fermentation O C O O C O NAD + NADH NADH NAD + NAD+ NADH NADH NAD+ C C C C CC C C C C C Glycolysis Alcoholic Glucoses C C C Fermentation C C Pyruvates Ethanols ADP ATP ADP ATP
  • 20. Chapter 8 20 FermentationSome cells ferment pyruvate to form acidsHuman muscle cells can perform fermentation • Anaerobic conditions produced when muscles use up O2 faster than it can be delivered (e.g. while sprinting) • Lactate (lactic acid) produced from pyruvate
  • 21. Chapter 8 21 Lactate Fermentation NAD+ NADH NADH NAD+ NAD+ NADH NADH NAD+ C C C C C CC C C C C C Glycolysis Lactate Glucoses C C C Fermentation C C C Pyruvates Lactates ADP ATP ADP ATP
  • 22. Chapter 8 22 Cellular RespirationIn eukaryotic cells, cellular respiration occurs within mitochondria, organelles with two membranes that produce two compartments • The inner membrane encloses a central compartment containing the fluid matrix • The outer membrane surrounds the organelle, producing an intermembrane space
  • 23. Chapter 8 23 A Mitochondrion One of Its Mitochondria a b A Cell A Crista Outer & Inner Membranes cIntermembrane Matrix Compartment
  • 24. Chapter 8 24 Cellular RespirationOverview of Aerobic Cellular Respiration:Glucose is first broken down into pyruvate, through glycolysis, in the cell cytoplasmPyruvate is transported into the mitochondrion (eukaryotes) and split into CO2 and a 2 carbon acetyl group
  • 25. Chapter 8 25 Cellular RespirationThe acetyl group is further broken down into CO2 in the Krebs Cycle (matrix space) as electron carriers are loadedElectron carriers loaded up in glycolysis and the Krebs Cycle give up electrons to the electron transport chain (ETC) along the inner mitochondrial membrane
  • 26. Chapter 8 26 Cellular RespirationA hydrogen ion gradient produced by the ETC is used to make ATP (chemiosmosis)ATP is transported out of the mitochondrion to provide energy for cellular activities
  • 27. Chapter 8 27CellularRespiration
  • 28. Chapter 8 28 Pyruvate Breakdown in MitochondriaAfter glycolysis, pyruvate diffuses into the mitochondrion into the matrix spacePyruvate is split into CO2 and a 2-carbon acetyl group, generating 1 NADH per pyruvate
  • 29. Chapter 8 29 Pyruvate Breakdown in MitochondriaAcetyl group is carried by a helper molecule called Coenzyme A, now called Acetyl CoAAcetyl CoA enters the Krebs Cycle and is broken down into CO2
  • 30. Chapter 8 30Pyruvate Breakdown in MitochondriaElectron carriers NAD+ and FAD are loaded with electrons to produce 3 NADH & 1 FADH2 per Acetyl CoA6. One ATP also made per Acetyl CoA in the Krebs Cycle
  • 31. Chapter 8 31 Formation of Acetyl CoA O O C C O C C C Pyruvates C C C ONAD+ NAD+NADH NADH C C C C C C CoA CoA CoA C C Acetyl CoA C C CoA
  • 32. Chapter 8 32 Krebs Cycle: SummaryCoA CoA C C Acetyl CoA C C CoA CoA 1 C C C C C C C C C C C CO C C C C C C C C O C NAD+ NAD+ CO O NADH NADH NADH NADH 2 3 C C C C C C NAD+ NAD+ C C C C CNAD+ H 2O H 2O 5 6 7 NAD+ FADH2NADH O FADH2 O NADH C FAD CADP O FAD O ADPATP ATP 4 C C C C C C C C C H 2O H 2O
  • 33. Chapter 8 33 Electron Transport ChainMost of the energy in glucose is stored in electron carriers NADH and FADH2 • Only 4 total ATP produced per glucose after complete breakdown in the Krebs Cycle
  • 34. Chapter 8 34 Electron Transport ChainNADH and FADH2 deposit electrons into electron transport chains in the inner mitochondrial membraneElectrons join with oxygen gas and hydrogen ions to made H2O at the end of the ETCs
  • 35. Mitochondrial Chapter 8 35Electron Transport System
  • 36. Chapter 8 36 ChemiosmosisEnergy is released from electrons as they are passed down the electron transport chainReleased energy used to pump hydrogen ions across the inner membrane • Hydrogen ions accumulate in intermembrane space
  • 37. Chapter 8 37 ChemiosmosisHydrogen ions form a concentration gradient across the membrane, a form of stored energyHydrogen ions flow back into the matrix through an ATP synthesizing enzyme • Process is called chemiosmosis
  • 38. Chapter 8 38 ChemiosmosisFlow of hydrogen ions provides energy to link 32-34 molecules of ADP with phosphate, forming 32-34 ATPATP then diffuses out of mitochondrion and used for energy-requiring activities in the cell
  • 39. Chapter 8 39MitochondrialChemiosmosis (1)
  • 40. Mitochondrial Chapter 8 40Chemiosmosis (2)
  • 41. Mitochondrial Chapter 8 41Chemiosmosis (3)
  • 42. Chapter 8 42 Influence on How Organisms FunctionMetabolic processes in cells are heavily dependent on ATP generation (cyanide kills by preventing this)Muscle cells switch between fermentation and aerobic cell respiration depending on O2 availability
  • 43. Chapter 8 43Energy Harvestedfrom Glucose
  • 44. Chapter 8 44 Energy Harvested from Glucose(Cytoplasm) Glucose 2 ATP Glycolysis 4 ATP 2 Pyruvates(Mitochondrial 2 NADH 2 NADH 2 CO2 Matrix) 6 NADH Krebs 4 CO2 2 FADH2 Cycle 2 ATP (InnerMembrane) Electron Transport Water Oxygen System 32 ATP
  • 45. Chapter 8The end