1. Chemiosmotic model.

2. Mitochondrial ATP Synthase Complex The proton-motive force causes rotation of the central shaft  This causes a conformational change within all the three  pairs The conformational change in one of the three pairs promotes condensation of ADP and P i into ATP

4. Figure 22-43Model of the E. coli F 1 F 0 –ATPase. Page 832

13. Rotational Catalysis

17. Movies http://atom.chem.wwu.edu/sacahill/472/atp %20synthase.movhttp://atom.chem.wwu.edu/sacahill/472/atp %20synthase.mov http://atom.chem.wwu.edu/sacahill/472/atp %20synthase2.movhttp://atom.chem.wwu.edu/sacahill/472/atp %20synthase2.mov http://atom.chem.wwu.edu/sacahill/472/rot arymech.movhttp://atom.chem.wwu.edu/sacahill/472/rot arymech.mov

21. Heat generation by uncoupled mitochondria. The uncoupling protein (thermogenin) in the mitochondria of brown adipose tissue, by providing an alternative route for protons to reenter the mitochondrial matrix, causes the energy conserved by proton pumping to be dissipated as heat.

22. Figure 22-46Uncoupling of oxidative phosphorylation. Page 834

23. ATP Yield From Glucose

24. Regulation of the ATP-producing pathways

25. Mitochondrial genes and mutations

27. Let’s Sing! Lyrics?

30. Light Energy is Converted to ATP in Plant Chloroplasts

33. Various Pigments Harvest the Light Energy The energy is transferred to the photosynthetic reaction center

44. Exciton and electron transfer. This generalized scheme shows conversion of the energy of an absorbed photon into separation of charges at the reaction center

47. photosynthetic machinery in purple bacteria and green sulfur bacteria

48. Photoreaction center of the purple bacterium Rhodopseudomonas viridis

49. Sequence of events following excitation of the special pair of bacteriochlorophylls with the time scale of the electron transfers in parentheses. 1 The excited special pair passes an electron to pheophytin, 2 from which the electron moves rapidly to the tightly bound menaquinone, QA. 3 This quinone passes electrons much more slowly to the diffusible ubiquinone, QB, through the nonheme Fe. Meanwhile, 4 the "electron hole" in the special pair is filled by an electron from a heme of cytochrome c.

50. Integration of photosystems I and II in chloroplasts. The "Z scheme"

51. Photosystem II of the cyanobacterium Synechococcus elongates

52. The supramolecular complex of PSI and its associated antenna chlorophylls

53. Electron and proton flow through the cytochrome b6f complex

54. Localization of PSI and PSII in thylakoid membranes

57. Water-splitting activity of the oxygen-evolving complex

58. Light-Induced Redox Reactions and Electron Transfer Cause Acidification of Lumen The proton-motive force across the thylakoid membrane drives the synthesis of ATP

60. Flow of Protons: Mitochondria, Chloroplasts, Bacteria According to endosymbiotic theory, mitochondria and chloroplasts arose from entrapped bacteria Bacterial cytosol became mitochondrial matrix and chloroplast stroma

66. CHAPTER 20 Carbohydrate Biosynthesis in Plants and Bacteria –CO 2 assimilation in photosynthetic organisms –Photorespiration in C 3 plants –Avoiding photorespiration in C 4 plants Key topics:

67. Introduction to Anabolic Pathways The previous chapters were mainly concerned with catabolism: how to extract energy from biomolecules This and the following chapters are concerned with anabolism: how to build biomolecules Plants are extremely versatile in biosynthesis –Can build organic compounds from CO 2 –Can use energy of sunlight to support biosynthesis –Can adopt to a variety of environmental situations

68. Assimilation of CO 2 by Plants

70. Plants and Photosynthetic Microorganisms Support the Life of Animals and Fungi Plants capture the energy from the ultimate energy source and make it available via carbohydrates to animals and fungi

73. CO 2 Assimilation Occurs in Plastids Organelles found in plants and algae Enclosed by a double membrane Have their own small genome The inner membrane is impermeable to ions such as H +, and to polar and charged molecules

75. Origin and Differentiation of Plastids Plastids were acquired during evolution by early eukaryotes via endosymbiosis of photosynthetic cyanobacteria Plastids reproduce asexually via binary fission The undifferentiated protoplastids in plants can differentiate into several types, each with a distinct function –Chloroplasts for photosynthesis –Amyloplasts for starch storage –Chromoplasts for pigment storage –Elaioplasts for lipid storage –Proteinoplasts for protein storage

77. CO 2 Assimilation The assimilation of carbon dioxide occurs in the stroma of chloroplasts via a cyclic process known as the Calvin cycle The key intermediate, ribulose 1,5-bisphosphate is constantly regenerated using energy of ATP The key enzyme, ribulose 1,5-bisphosphate carboxylase / oxygenase (Rubisco), is probably the most abundant protein on Earth The net result is the reduction of CO 2 with NADPH that was generated in the light reactions of photosynthesis

79. The Calvin Cycle

81. The Structure and Function of Rubisco Rubisco is a large Mg ++ -containing enzyme that makes a new carbon-carbon bond using CO 2 as a substrate

84. Rubisco’s Carboxylase Activity

91. Catalytic Role of Mg ++ in Rubisco’s Carboxylase Activity Notice that Mg ++ is held by negatively charged side chains of glutamate, aspartate, and carbamoylated lysine Mg ++ brings together the reactants in a correct orientation, and stabilizes the negative charge that forms upon the nucleophilic attack of enediolate to CO 2

93. Rubisco is Activated via Covalent Modification of the Active Site Lysine

95. Synthesis of Glyceraldehyde-3 Phosphate (First Stage) Three rounds of the Calvin cycle fixes three CO 2 molecules and produces one molecule of 3- phosphoglycerate

97. Fate of Glyceraldehyde 3- phosphate (Second Stage) Converted to starch in the chloroplast Converted to sucrose for export Recycled to ribulose 1,5-bisphosphate

99. Interconversion of Triose Phosphates and Pentose Phosphates This is how ribulose 1,5-bisphosphate is regenerated in the third stage of the Calvin cycle

100. Sugar interconversions

103. Formation of Five- and Seven- Carbon Sugars

104. Synthesis of Ribulose 1,5- bisphosphate

105. Transketolase Reactions

108. Transketolase Uses Thiamine Pyrophosphate as the Cofactor

110. Stoichiometry and Energy Cost of CO 2 Assimilation Fixation of three CO 2 molecules yields one glyceraldehyde 3-phosphate Nine ATP molecules and six NADPH molecules are consumed

112. Photosynthesis: From Light and CO 2 to Glyceraldehyde 3- phosphate The photosynthesis of one molecule of glyceraldehyde 3-phosphate requires the capture of roughly 24 photons

113. ATP and NADPH produced by the light reactions are essential substrates for the reduction of CO 2

114. Enzymes in the Calvin Cycle are Regulated by Light Target enzymes are –ribulose 5-phosphate kinase, –fructose 1,6-bisphosphatase, –seduloheptose 1,7-bisphosphatase, and –glyceraldehyde 3-phosphate dehydrogenase

115. Light activation of several enzymes of the Calvin cycle

116. Photorespiration So far, we saw that plants oxidize water to O 2 and reduce CO 2 to carbohydrates during the photosynthesis Plants also have mitochondria where usual respiration with consumption of O 2 occurs in the dark In addition, a wasteful side reaction catalyzed by Rubisco occurs in mitochondria This reaction consumes oxygen and is called photorespiration; unlike mitochondrial respiration, this process does not yield energy

117. Oxygenase Activity of Rubisco The reactive nucleophile in the Rubisco reaction is the electron-rich enediol form of ribulose 1,5- bisphosphate The active site meant for CO 2 also accommodates O 2 Mg ++ also stabilizes the hydroperoxy anion that forms by electron transfer from the enediol to oxygen

119. Salvage of 2- Phosphoglycerate Complex ATP-consuming process for the recovery of C 2 fragments from the photorespiration Requires oxidation of glycolate with molecular oxygen in peroxisomes, and formation of H 2 O 2 Involves a loss of a carbon as CO 2 by mitochondrial decarboxylation of glycine

120. Glycolate pathway

121. Rubisco in C 3 Plants Cannot Avoid Oxygen Plants that assimilate dissolved CO 2 in the mesophyll of the leaf into three-carbon 3- phosphoglycerate are called the C 3 plants Our atmosphere contains about 21% of oxygen and 0.038% of carbon dioxide The dissolved concentrations in pure water are about 260  M O 2 and 11  M CO 2 (at the equilibrium and room temperature) The K m of Rubisco for oxygen is about 350  M

122. Separation of CO 2 capture and the Rubisco Reaction in C 4 Plants Many tropical plants avoid wasteful photorespiration by a physical separation of CO 2 capture and Rubisco activity CO 2 is captured into oxaloacetate (C 4 ) in mesophyll cells CO 2 is transported to bundle-sheath cells where Rubisco is located The local concentration of CO 2 in bundle-sheath cells is much higher than the concentration of O 2

123. Carbon assimilation in C4 plants

124. Chapter 20: Summary ATP and NADPH from light reactions are needed in order to assimilate CO 2 into carbohydrates Assimilations of three CO 2 molecules via the Calvin cycle leads to the formation of one molecule of 3-phosphoglycerate 3-Phosphoglycerate is a precursor for the synthesis of larger carbohydrates such as fructose and starch The key enzyme of the Calvin cycle, Rubisco, fixes carbon dioxide into carbohydrates Low selectivity of Rubisco causes a wasteful incorporation of molecular oxygen in C 3 plants; this is avoided in C 4 plants by increasing the concentration of CO 2 near Rubisco In this chapter, we learned that: