1. Pathways that Harvest and Store Chemical Energy6
Pathways that Harvest and Store Chemical Energy

2. Energy flow and chemical recycling in ecosystems

3. Five principles governing metabolic pathways:
Concept 6.1 ATP, Reduced Coenzymes, and Chemiosmosis Play Important Roles in Biological Energy Metabolism
Five principles governing metabolic pathways:
Chemical transformations occur in a series of intermediate reactions that form a metabolic pathway.
Each reaction is catalyzed by a specific enzyme.
Most metabolic pathways are similar in all organisms.

4. Concept 6.1 ATP, Reduced Coenzymes, and Chemiosmosis Play Important Roles in Biological Energy Metabolism
In eukaryotes, many metabolic pathways occur inside specific organelles.
Each metabolic pathway is controlled by enzymes that can be inhibited or activated.

5. Figure 6.1 The Concept of Coupling Reactions

6. Figure 9.2 A review of how ATP drives cellular work

7. Figure 6.2 ATP

8. Substrate-level phosphorylation

9. Reduction is the gain of one or more electrons.
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.

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

11. Methane combustion as an energy-yielding redox reaction

12. NAD+ as an electron shuttle

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

14. Oxidative phosphorylation couples oxidation of NADH:
Concept 6.1 ATP, Reduced Coenzymes, and Chemiosmosis Play Important Roles in Biological Energy Metabolism
Oxidative phosphorylation couples oxidation of NADH:
with production of ATP:

15. Figure 6.5 A Chemiosmosis

16. Figure 6.5 B Chemiosmosis

17. Figure 6.8 Energy Metabolism Occurs in Small Steps

18. Figure 6.9 Energy-Releasing Metabolic Pathways

19. An overview of cellular respiration

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

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

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

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

24. Examples of reaction types common in metabolic pathways:
Concept 6.2 Carbohydrate Catabolism in the Presence of Oxygen Releases a Large Amount of Energy
Examples of reaction types common in metabolic pathways:
Step 6: Oxidation–reduction
Step 7: Substrate-level phosphorylation
text art pg 107 here

25. Products: CO2 and acetate; acetate is then bound to coenzyme A (CoA)
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)

26. Figure 6.11 The Citric Acid Cycle

27. Final reaction of citric acid cycle:
Concept 6.2 Carbohydrate Catabolism in the Presence of Oxygen Releases a Large Amount of Energy
Final reaction of citric acid cycle:

28. Figure 6.12 Electron Transport and ATP Synthesis in Mitochondria

29. 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.
The role of O2: most of the ATP produced is formed by oxidative phosphorylation, which is due to the reoxidation of NADH.
APPLY THE CONCEPT Carbohydrate catabolism in the presence of oxygen releases a large amount of energy

30. Under anaerobic conditions, NADH is reoxidized by fermentation.
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.

31. Lactic acid fermentation: End product is lactic acid (lactate).
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+.

32. Figure 6.13 A Fermentation

33. Alcoholic fermentation: End product is ethyl alcohol (ethanol).
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.

34. Figure 6.13 B Fermentation

35. Figure 6.14 Relationships among the Major Metabolic Pathways of the Cell

36. Concept 6.4 Catabolic and Anabolic Pathways Are Integrated
Catabolism:
Polysaccharides are hydrolyzed to glucose, which enter glycolysis.
Lipids break down to fatty acids and glycerol. Fatty acids can be converted to acetyl CoA.
Proteins are hydrolyzed to amino acids that can feed into glycolysis or the citric acid cycle.

37. How DO cells break down a triglyceride to produce ATP?
b-oxidation!

38. Concept 6.4 Catabolic and Anabolic Pathways Are Integrated
Anabolism:
Many catabolic pathways can operate in reverse.
Gluconeogenesis—citric acid cycle and glycolysis intermediates can be reduced to form glucose.
Acetyl CoA can be used to form fatty acids.
Some citric acid intermediates can form nucleic acids.

39. The control of cellular respiration 

40. Photosynthesis involves two pathways:
Concept 6.5 During Photosynthesis, Light Energy Is Converted to Chemical Energy
Photosynthesis involves two pathways:
Light reactions convert light energy into chemical energy (in ATP and the reduced electron carrier NADPH).
Carbon-fixation reactions use the ATP and NADPH, along with CO2, to produce carbohydrates.

41. Figure 6.15 An Overview of Photosynthesis

42. Concept 6.5 During Photosynthesis, Light Energy Is Converted to Chemical Energy
Light is a form of electromagnetic radiation, which travels as a wave but also behaves as particles (photons).
Photons can be absorbed by a molecule, adding energy to the molecule—it moves to an excited state.

43. Figure 6.16 The Electromagnetic Spectrum

44. Figure 10.6 Why leaves are green: interaction of light with chloroplasts

45. Pigments: molecules that absorb wavelengths in the visible spectrum.
Concept 6.5 During Photosynthesis, Light Energy Is Converted to Chemical Energy
Pigments: molecules that absorb wavelengths in the visible spectrum.
Chlorophyll absorbs blue and red light; the remaining light is mostly green.
Absorption spectrum—plot of light energy absorbed against wavelength.
Action spectrum—plot of the biological activity of an organism against the wavelengths to which it is exposed

46. Determining an absorption spectrum

47. Figure 6.17 Absorption and Action Spectra

48. Evidence that chloroplast pigments participate in photosynthesis: absorption and action spectra for photosynthesis in an alga

49. Figure 6.18 The Molecular Structure of Chlorophyll (Part 1)

50. Figure 6.18 The Molecular Structure of Chlorophyll (Part 2)

51. Excitation of isolated chlorophyll by light

52. Figure 6.19 Noncyclic Electron Transport Uses Two Photosystems

53. A mechanical analogy for the light reactions

54. ATP is needed for carbon-fixation pathways.
Concept 6.5 During Photosynthesis, Light Energy Is Converted to Chemical Energy
ATP is needed for carbon-fixation pathways.
Cyclic electron transport uses only photosystem I and produces ATP; an electron is passed from an excited chlorophyll and recycles back to the same chlorophyll.

55. Cyclic electron flow

56. The light reactions and chemiosmosis: the organization of the thylakoid membrane

57. Figure 6.21 The Calvin Cycle

58. CO2 is added to ribulose 1,5-bisphosphate (RuBP).
Concept 6.6 Photosynthetic Organisms Use Chemical Energy to Convert CO2 to Carbohydrates
1. Fixation of CO2:
CO2 is added to ribulose 1,5-bisphosphate (RuBP).
Ribulose bisphosphate carboxylase/oxygenase (rubisco) catalyzes the reaction.
A 6-carbon molecule results, which quickly breaks into two 3-carbon molecules: 3- phosphoglycerate (3PG).
VIDEO 6.2 Rubisco: A three-dimensional model

59. Figure 6.22 RuBP Is the Carbon Dioxide Acceptor

60. 2. 3PG is reduced to form glyceraldehyde 3- phosphate (G3P).
Concept 6.6 Photosynthetic Organisms Use Chemical Energy to Convert CO2 to Carbohydrates
2. 3PG is reduced to form glyceraldehyde 3- phosphate (G3P).

61. C4 leaf anatomy and the C4 pathway

62. C4 and CAM photosynthesis compared

63. A review of photosynthesis