1 / 73

Cellular Respiration

Cellular Respiration. A.P. Biology. Light energy. ECOSYSTEM. Photosynthesis in chloroplasts. Organic molecules. CO 2 + H 2 O. + O 2. Cellular respiration in mitochondria. ATP. powers most cellular work . Heat energy. Figure 9.2. Energy.

Download Presentation

Cellular Respiration

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.


Presentation Transcript

  1. Cellular Respiration A.P. Biology

  2. Light energy ECOSYSTEM Photosynthesisin chloroplasts Organicmolecules CO2 + H2O + O2 Cellular respirationin mitochondria ATP powers most cellular work Heatenergy Figure 9.2 Energy • Flows into an ecosystem as sunlight and leaves as heat

  3. Catabolic pathways yield energy by oxidizing organic fuels • The breakdown of organic molecules is exergonic • Fermentation • Is a partial degradation of sugars that occurs without oxygen

  4. Catabolic pathways yield energy by oxidizing organic fuels • Cellular respiration • Is the most prevalent and efficient catabolic pathway • Consumes oxygen and organic molecules such as glucose • Yields ATP

  5. Redox Reactions: Oxidation and Reduction • Catabolic pathways yield energy • Due to the transfer of electrons • Redox reactions • Transfer electrons from one reactant to another by oxidation and reduction • Oxidation • A substance loses electrons, or is oxidized • Reduction • A substance gains electrons, or is reduced

  6. becomes oxidized(loses electron) becomes reduced(gains electron)

  7. Products Reactants becomes oxidized + + + Energy 2O2 CO2 2 H2O CH4 becomes reduced H C C O O O O H O H H H H Oxygen(oxidizingagent) Methane(reducingagent) Carbon dioxide Water Figure 9.3 Some redox reactions • Do not completely exchange electrons • Change the degree of electron sharing in covalent bonds

  8. becomes oxidized C6H12O6 + 6O2 6CO2 + 6H2O + Energy becomes reduced Oxidation of Organic Fuel Molecules During Cellular Respiration • During cellular respiration • Glucose is oxidized and oxygen is reduced G = -686 kcal/mol

  9. H2 + 1/2 O2 Explosiverelease ofheat and lightenergy (a) Uncontrolled reaction Free energy, G Figure 9.5 A H2O Step by step catabolism of glucose • If electron transfer is not stepwise • A large release of energy occurs • As in the reaction of hydrogen and oxygen to form water

  10. 2 H + 1/2 O2 (from food via NADH) Controlled release of energy for synthesis ofATP 2 H+ + 2 e– ATP ATP Free energy, G Electron transport chain ATP 2 e– 1/2 O2 2 H+ H2O Figure 9.5 B (b) Cellular respiration ETC • The electron transport chain • Passes electrons in a series of steps • Uses the energy from the electron transfer to form ATP

  11. 2 e– + 2 H+ 2 e– + H+ NAD+ NADH H Dehydrogenase O O H H Reduction of NAD+ + + 2[H] C NH2 NH2 C (from food) Oxidation of NADH N N+ Nicotinamide(reduced form) Nicotinamide(oxidized form) CH2 O O O O– P O H H OH O O– HO P NH2 HO CH2 O N N H N H N O H H HO OH Figure 9.4 NAD – Nicotinamide Adenine Dinucleotide(Electron Acceptor) • Electrons from organic compounds • Are usually 1st transferred to NAD+, a coenzyme Dehydragenase – removes 2 hydrogen atoms

  12. NADH • NADH, the reduced form of NAD+ • Passes the electrons to the electron transport chain • Electrons are ultimately passed to a molecule of oxygen (Final electron acceptor) G = -53 kcal/mol Electron path in respiration Food  NADH  ETC  Oxygen

  13. Cellular Respiration • Respiration is a cumulative function of three metabolic stages • Glycolysis • The citric acid cycle (TCA or Krebbs) • Oxidative phosphorylation C6H12O6+ 6O2   <---->   6 CO2+ 6 H20    + e- --->    36-38 ATPDG =  -686 Kc/mole                                263Kc  = 38%

  14. Respiration • Glycolysis • Breaks down glucose into two molecules of pyruvate • The citric acid cycle • Completes the breakdown of glucose • Oxidative phosphorylation • Is driven by the electron transport chain • Generates ATP

  15. Electrons carried via NADH and FADH2 Electrons carried via NADH Oxidativephosphorylation:electron transport andchemiosmosis Citric acid cycle Glycolsis Pyruvate Glucose Cytosol Mitochondrion ATP ATP ATP Substrate-level phosphorylation Oxidative phosphorylation Substrate-level phosphorylation Figure 9.6 Respiration Overview 2 ATP 2 ATP 34 ATP

  16. Aerobic Respiration Substrates

  17. Enzyme Enzyme ADP P Substrate + ATP Product Figure 9.7 Substrate Level Phosphorylation • Both glycolysis and the citric acid cycle • Can generate ATP by substrate-level phosphorylation

  18. Oxidativephosphorylation Glycolysis Citricacidcycle ATP ATP ATP Energy investment phase Glucose 2 ATP + 2 used 2 ATP P Energy payoff phase formed 4 ATP 4 ADP + 4 P 2 NADH 2 NAD+ + 4 e- + 4 H + + 2 H+ 2 Pyruvate + 2 H2O Glucose 2 Pyruvate + 2 H2O 4 ATP formed – 2 ATP used 2 ATP + 2 H+ 2 NAD+ + 4 e– + 4 H + 2 NADH Figure 9.8 Glycolysis • Harvests energy by oxidizing glucose to pyruvate • Glycolysis • Means “splitting of sugar” • Breaks down glucose into pyruvate • Occurs in the cytoplasm of the cell • Two major phases • Energy investment phase • Energy payoff phase

  19. Energy Investment Phase

  20. Energy Payoff Phase

  21. Glycolysis Summary

  22. The First Stage of Glycolysis • Glucose (6C) is broken down into 2 PGAL's (3C) • This requires two ATP's

  23. The Second Stage of Glycolysis • 2 PGAL's (3C) are converted to 2 pyruvates • This creates 4 ATP's and 2 NADH's • The net ATP production of Glycolysis is 2 ATP's

  24. Citric Acid Cyclea.k.a. Krebs Cycle • Completes the energy-yielding oxidation of organic molecules • The citric acid cycle • Takes place in the matrix of the mitochondrion

  25. Krebs's Cycle (citric acid cycle, TCA cycle) • Goal: take pyruvate and put it into the Krebs's cycle, producing NADH and FADH2 • Where: the mitochondria • There are two steps • The Conversion of Pyruvate to Acetyl CoA • The Kreb's Cycle proper • In the Krebs's cycle, all of Carbons, Hydrogens, and Oxygeng in pyruvate end up as CO2 and H2O • The Krebs's cycle produces 2 ATP's, 8 NADH's, and 2FADH2's per glucose molecule

  26. Fate of Pyruvate

  27. Carboxyl (coo-) is cleaved CO2 is released

  28. CYTOSOL MITOCHONDRION + H+ NAD+ NADH O– CoA S 2 C O C O C O CH3 1 3 CH3 Acetyle CoA Pyruvate CO2 Coenzyme A Transport protein Figure 9.10 Before the citric acid cycle can begin • Pyruvate must first be converted to acetyl CoA, which links the cycle to glycolysis

  29. Pyruvate(from glycolysis,2 molecules per glucose) Oxidativephosphorylation Glycolysis Citricacidcycle ATP ATP ATP CO2 CoA NADH + 3 H+ Acetyle CoA CoA CoA Citricacidcycle 2 CO2 3 NAD+ FADH2 FAD 3 NADH + 3 H+ ADP + Pi ATP Figure 9.11 An overview of the citric acid cycle

  30. Citric acid cycle Oxidative phosphorylation Glycolysis S CoA C O CH3 Acetyl CoA CoA SH H2O O C COO– NADH 1 COO– CH2 + H+ COO– CH2 COO– NAD+ Oxaloacetate 8 C COO– HO CH2 2 CH2 HC COO– COO– COO– HO CH HO CH Malate Citrate COO– CH2 Isocitrate COO– CO2 Citric acid cycle 3 H2O 7 NAD+ COO– NADH COO– CH + H+ Fumarate CH2 CoA SH HC a-Ketoglutarate CH2 COO– C O 4 6 SH CoA COO– COO– COO– CH2 5 CH2 FADH2 CO2 CH2 CH2 NAD+ FAD C O COO– Succinate NADH CoA S P i + H+ Succinyl CoA GDP GTP ADP ATP Figure 9.12

  31. The Kreb's Cycle • 6 NADH's are generated • 2 FADH2 is generated • 2 ATP are generated • 4 CO2's are released

  32. Net Engergy Production from Aerobic Respiration • Glycolysis: 2 ATP • Kreb's Cycle: 2 ATP • Electron Transport Phosphorylation: 32 ATP • Each NADH produced in Glycolysis is worth 2 ATP (2 x 2 = 4) - the NADH is worth 3 ATP, but it costs an ATP to transport the NADH into the mitochondria, so there is a net gain of 2 ATP for each NADH produced in gylcolysis • Each NADH produced in the conversion of pyruvate to acetyl COA and Kreb's Cycle is worth 3 ATP (8 x 3 = 24) • Each FADH2 is worth 2 ATP (2 x 2 = 4) • 4 + 24 + 4 = 32 • Net Energy Production: 36 ATP

  33. Energy Yields: • Glucose: 686 kcal/mol • ATP: 7.5 kcal/mol • 7.5 x 36 = 270 kcal/mol for all ATP's produced • 270 / 686 = 39% energy recovered from aerobic respiration

  34. After the Krebs Cycle… • During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis • NADH and FADH2 • Donate electrons to the electron transport chain, which powers ATP synthesis via oxidative phosphorylation

  35. The Pathway of Electron Transport • In the electron transport chain • Electrons from NADH and FADH2 lose energy in several steps • At the end of the chain • Electrons are passed to oxygen, forming water

  36. NADH 50 FADH2 Multiproteincomplexes I 40 FAD FMN II Fe•S Fe•S O III Cyt b Fe•S 30 Cyt c1 IV Cyt c Free energy (G) relative to O2 (kcl/mol) Cyt a Cyt a3 20 10 O2 0 2 H + + 12 Figure 9.13 H2O

  37. INTERMEMBRANE SPACE A rotor within the membrane spins clockwise whenH+ flows past it down the H+ gradient. H+ H+ H+ H+ H+ H+ H+ A stator anchoredin the membraneholds the knobstationary. A rod (for “stalk”)extending into the knob alsospins, activatingcatalytic sites inthe knob. H+ Three catalytic sites in the stationary knobjoin inorganic Phosphate to ADPto make ATP. ADP + ATP P i MITOCHONDRIAL MATRIX Figure 9.14 Chemiosmosis: The Energy-Coupling Mechanism • ATP synthase • Is the enzyme that actually makes ATP

  38. ETC • Electron transfer causes protein complexes to pump H+ from the mitochondrial matrix to the intermembrane space • The resulting H+ gradient • Stores energy • Drives chemiosmosis in ATP synthase • Is referred to as a proton-motive force

  39. Chemiosmosis • Is an energy-coupling mechanism that uses energy in the form of a H+ gradient across a membrane to drive cellular work H+ gradient = Proton motive force

  40. Inner Mitochondrial membrane Oxidative phosphorylation. electron transport and chemiosmosis Glycolysis ATP ATP ATP H+ H+ H+ H+ Cyt c Protein complex of electron carners Intermembrane space Q IV I III ATP synthase Inner mitochondrial membrane II H2O FADH2 2 H+ + 1/2 O2 FAD+ NADH+ NAD+ ATP ADP + P i (Carrying electrons from, food) H+ Mitochondrial matrix Chemiosmosis ATP synthesis powered by the flow Of H+ back across the membrane Electron transport chain Electron transport and pumping of protons (H+), which create an H+ gradient across the membrane Figure 9.15 Oxidative phosphorylation

  41. An Accounting of ATP Production by Cellular Respiration • During respiration, most energy flows in this sequence • Glucose to NADH to electron transport chain to proton-motive force to ATP

  42. Electron shuttles span membrane MITOCHONDRION CYTOSOL 2 NADH or 2 FADH2 2 FADH2 2 NADH 2 NADH 6 NADH Glycolysis Oxidative phosphorylation: electron transport and chemiosmosis Citric acid cycle 2 Acetyl CoA 2 Pyruvate Glucose + 2 ATP + 2 ATP + about 32 or 34 ATP by substrate-level phosphorylation by substrate-level phosphorylation by oxidative phosphorylation, depending on which shuttle transports electrons from NADH in cytosol About 36 or 38 ATP Maximum per glucose: Figure 9.16

More Related