Pathways that Harvest and Store Chemical Energy

1. 6 Pathways that Harvest andStore Chemical Energy

2. Chapter 6 Pathways that Harvest and Store Chemical Energy • Key Concepts • 6.1 ATP, Reduced Coenzymes, and Chemiosmosis Play Important Roles in Biological Energy Metabolism • 6.2 Carbohydrate Catabolism in the Presence of Oxygen Releases a Large Amount of Energy • 6.3 Carbohydrate Catabolism in the Absence of Oxygen Releases a Small Amount of Energy

3. Chapter 6 Pathways that Harvest and Store Chemical Energy 6.4 Catabolic and Anabolic Pathways Are Integrated 6.5 During Photosynthesis, Light Energy Is Converted to Chemical Energy 6.6 Photosynthetic Organisms Use Chemical Energy to Convert CO2 to Carbohydrates

4. Concept 6.1 ATP, Reduced Coenzymes, and Chemiosmosis Play Important Roles in Biological Energy Metabolism Energy is stored in chemical bonds and can be released and transformed by metabolic pathways. Chemical energy available to do work is termed free energy (G).

5. Concept 6.1 ATP, Reduced Coenzymes, and Chemiosmosis Play Important Roles in Biological Energy Metabolism In cells, energy-transforming reactions are often coupled: An energy-releasing (exergonic) reaction is coupled to an energy-requiring (endergonic) reaction.

6. Concept 6.1 ATP, Reduced Coenzymes, and Chemiosmosis Play Important Roles in Biological Energy Metabolism Adenosine triphosphate (ATP) is a kind of “energy currency” in cells. Energy released by exergonic reactions is stored in the bonds of ATP. When ATP is hydrolyzed, free energy is released to drive endergonic reactions.

7. Figure 6.1 The Concept of Coupling Reactions

8. Figure 6.2 ATP

9. Concept 6.1 ATP, Reduced Coenzymes, and Chemiosmosis Play Important Roles in Biological Energy Metabolism Hydrolysis of ATP is exergonic:

10. Concept 6.1 ATP, Reduced Coenzymes, and Chemiosmosis Play Important Roles in Biological Energy Metabolism Free energy of the bond between phosphate groups is much higher than the energy of the O—H bond that forms after hydrolysis. text art pg 102 here (1st one, in left-hand column)

11. Concept 6.1 ATP, Reduced Coenzymes, and Chemiosmosis Play Important Roles in Biological Energy Metabolism Energy can also be transferred by the transfer of electrons in oxidation–reduction, or redox reactions. Reduction is the gain of one or more electrons. • Oxidation is the loss of one or more electrons. Transfer of hydrogen atoms involves transfer of electrons. So when a molecule loses a H, it is oxidized, when it gains a H, it is reduced. (H = H+ + e–)

12. Concept 6.1 ATP, Reduced Coenzymes, and Chemiosmosis Play Important Roles in Biological Energy Metabolism Oxidation and reduction always occur together.

13. Concept 6.1 ATP, Reduced Coenzymes, and Chemiosmosis Play Important Roles in Biological Energy Metabolism The more reduced a molecule is, the more energy is stored in its bonds. Energy is transferred in a redox reaction. Energy in the reducing agent is transferred to the reduced product.

14. Figure 6.3 Oxidation, Reduction, and Energy

15. Concept 6.1 ATP, Reduced Coenzymes, and Chemiosmosis Play Important Roles in Biological Energy Metabolism Coenzyme NAD+ is a key electron carrier in redox reactions. NAD+ (oxidized form) NADH (reduced form)

16. Figure 6.4 A NAD+/NADH Is an Electron Carrier in Redox Reactions

17. Concept 6.1 ATP, Reduced Coenzymes, and Chemiosmosis Play Important Roles in Biological Energy Metabolism Reduction of NAD+ is highly endergonic, storing energy. Oxidation of NADH is highly exergonic, releasing energy.

18. Figure 6.4 B NAD+/NADH Is an Electron Carrier in Redox Reactions

19. Concept 6.1 ATP, Reduced Coenzymes, and Chemiosmosis Play Important Roles in Biological Energy Metabolism In cells, energy is released in catabolism by oxidation and trapped by reduction of coenzymes such as NADH. • Energy for anabolic processes is supplied by ATP. .

20. Concept 6.1 ATP, Reduced Coenzymes, and Chemiosmosis Play Important Roles in Biological Energy Metabolism Cellular respiration is a major catabolic pathway. Glucose is oxidized: C6H12O6 + 6O2 >>>>6CO2 + 6H2O + energy Photosynthesis is a major anabolic pathway. Light energy is converted to chemical energy: 6CO2 + 6H2O >>>>C6H12O6 + 6O2

21. Concept 6.2 Carbohydrate Catabolism in the Presence of Oxygen Releases a Large Amount of Energy Cellular Respiration A lot of energy is released when reduced molecules with many C—C and C—H bonds are fully oxidized to CO2. Oxidation occurs in a series of small steps in three pathways: 1. glycolysis 2. pyruvate oxidation 3. citric acid cycle 4. ETC/ Oxidative phosphorylation.

22. Figure 6.8 Energy Metabolism Occurs in Small Steps

23. Figure 6.9 Energy-Releasing Metabolic Pathways

24. An overview of cellular respiration NADH High-energy electrons carried by NADH NADH FADH2 and OXIDATIVE PHOSPHORYLATION (Electron Transport and Chemiosmosis) GLYCOLYSIS CITRIC ACID CYCLE Glucose Pyruvate Mitochondrion Cytoplasm ATP CO2 CO2 ATP ATP Substrate-level phosphorylation Substrate-level phosphorylation Oxidative phosphorylation 0 Figure 6.6

25. Concept 6.2 Carbohydrate Catabolism in the Presence of Oxygen Releases a Large Amount of Energy Glycolysis: ten reactions. It is anaerobic. Takes place in the cytosol. Final products: 2 molecules of pyruvate (pyruvic acid) 2 molecules of ATP 2 molecules of NADH

26. Figure 6.10 Glycolysis Converts Glucose into Pyruvate (Part 1)

27. Figure 6.10 Glycolysis Converts Glucose into Pyruvate (Part 2)

28. Figure 6.10 Glycolysis Converts Glucose into Pyruvate (Part 3)

29. Concept 6.2 Carbohydrate Catabolism in the Presence of Oxygen Releases a Large Amount of Energy Pyruvate Oxidation: Products: CO2 and acetate; acetate is then bound to coenzyme A (CoA) Mitochondria. Aerobic.

30. Concept 6.2 Carbohydrate Catabolism in the Presence of Oxygen Releases a Large Amount of Energy Citric Acid Cycle: Mitochondria. Aerobic. 8 reactions, operates twice for every glucose molecule that enters glycolysis. Starts with Acetyl CoA with its 2 carbons being combined with Oxaloacetate, a 4 carbon compound. Oxaloacetate is regenerated in the last step, ensuring that the cycle can continue

31. Figure 6.11 The Citric Acid Cycle

32. For each turn of the cycle Two CO2 molecules are released The energy yield is one ATP, three NADH, and one FADH2 CoA Acetyl CoA CoA 2 carbons enter cycle Oxaloacetate 1 Citrate + H+ NADH 5 CO2 leaves cycle NAD+ 2 CITRIC ACID CYCLE NAD+ +H+ Malate NADH + P ADP FADH2 4 ATP Alpha-ketoglutarate FAD 3 CO2 leaves cycle Succinate + H+ NAD+ NADH Step 2 4 Steps 1 3 Steps and 5 and Acetyl CoA stokes the furnace. NADH, ATP, and CO2 are generated during redox reactions. Redox reactions generate FADH2 and NADH. Figure 6.9B

33. http://bcs.whfreeman.com/webpub/Ektron/pol1e/Activities/act0602/act_0602_citric_acid_cycle.htmlhttp://bcs.whfreeman.com/webpub/Ektron/pol1e/Activities/act0602/act_0602_citric_acid_cycle.htmlhttp://bcs.whfreeman.com/webpub/Ektron/pol1e/Activities/act0602/act_0602_citric_acid_cycle.htmlhttp://bcs.whfreeman.com/webpub/Ektron/pol1e/Activities/act0602/act_0602_citric_acid_cycle.html

34. ELECTRON TRANSPORT CHAIN, CHEMIOSMOSIS, AND OXIDATIVE PHOSPHORYLATION. • Inner mitochondrial membrane. • Aerobic.

35. Concept 6.2 Carbohydrate Catabolism in the Presence of Oxygen Releases a Large Amount of Energy Electron transport/ATP Synthesis: NADH is reoxidized to NAD+ and O2 is reduced to H2O in a series of steps. Respiratory chain—series of redox carrier proteins embedded in the inner mitochondrial membrane. Electron transport—electrons from the oxidation of NADH and FADH2 pass from one carrier to the next in the chain.

36. Oxidative phosphorylation couples oxidation of NADH: with production of ATP:

37. Concept 6.1 ATP, Reduced Coenzymes, and Chemiosmosis Play Important Roles in Biological Energy Metabolism The coupling is chemiosmosis—diffusion of protons across a membrane, which drives the synthesis of ATP. Chemiosmosis converts potential energy of a proton gradient across a membrane into the chemical energy in ATP.

38. 0 • Most ATP production occurs by oxidative phosphorylation • Electrons from NADH and FADH2 • Travel down the electron transport chain to oxygen, which picks up H+ to form water • Energy released by the redox reactions • Is used to pump H+ into the space between the mitochondrial membranes

39. Figure 6.12 Electron Transport and ATP Synthesis in Mitochondria

40. Figure 6.5 A Chemiosmosis

41. Figure 6.5 B Chemiosmosis

42. https://youtu.be/q-fKQuZ8dco

43. http://bcs.whfreeman.com/webpub/Ektron/pol1e/Animated Tutorials/at0602/at_0602_e_trans_atp_syn.html

44. Concept 6.2 Carbohydrate Catabolism in the Presence of Oxygen Releases a Large Amount of Energy About 32 molecules of ATP are produced for each fully oxidized glucose.

45. Concept 6.3 Carbohydrate Catabolism in the Absence of Oxygen Releases a Small Amount of Energy Under anaerobic conditions, NADH is reoxidized by fermentation. There are many different types of fermentation, but all operate to regenerate NAD+. The overall yield of ATP is only two—the ATP made in glycolysis.

46. Concept 6.3 Carbohydrate Catabolism in the Absence of Oxygen Releases a Small Amount of Energy Lactic acid fermentation: End product is lactic acid (lactate). NADH is used to reduce pyruvate to lactic acid, thus regenerating NAD+.

47. Figure 6.13 A Fermentation

48. Concept 6.3 Carbohydrate Catabolism in the Absence of Oxygen Releases a Small Amount of Energy Alcoholic fermentation: End product is ethyl alcohol (ethanol). Pyruvate is converted to acetaldehyde, and CO2 is released. NADH is used to reduce acetaldehyde to ethanol, regenerating NAD+ for glycolysis.

49. Figure 6.13 B Fermentation

50. http://bcs.whfreeman.com/webpub/Ektron/pol1e/Activities/act0604/act_0604_glycolysis_and_fermentation.htmlhttp://bcs.whfreeman.com/webpub/Ektron/pol1e/Activities/act0604/act_0604_glycolysis_and_fermentation.htmlhttp://bcs.whfreeman.com/webpub/Ektron/pol1e/Activities/act0604/act_0604_glycolysis_and_fermentation.htmlhttp://bcs.whfreeman.com/webpub/Ektron/pol1e/Activities/act0604/act_0604_glycolysis_and_fermentation.html