* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Chapter 11
Survey
Document related concepts
Evolution of metal ions in biological systems wikipedia , lookup
Adenosine triphosphate wikipedia , lookup
Electron transport chain wikipedia , lookup
Basal metabolic rate wikipedia , lookup
Biosequestration wikipedia , lookup
Citric acid cycle wikipedia , lookup
Microbial metabolism wikipedia , lookup
Oxidative phosphorylation wikipedia , lookup
Biochemistry wikipedia , lookup
Light-dependent reactions wikipedia , lookup
Transcript
Slide 1 Chapter 11: Phototrophic Energy Metabolism: Photosynthesis Slide 2 Photoheterotrophs vs. Photoautotrophs Slide 3 Photosynthesis Overview • Energy Transduction Reactions (aka the “light reactions”) • Light energy is captured by chlorophyll • Reducing power is generated in the form of NADPH • Carbon Assimilation Reactions (aka the “dark reactions”, the Calvin cycle) • Carbon dioxide is fixed and reduced Slide 4 The Chloroplast Slide 5 Slide 6 Cyanobacterium Slide 7 Light • Electromagnetic radiation with both wave and particle properties • Photon – discreet particle of light • Quantum – packet of energy carried by the photon • Energy carried by photon is inversely proportional to the wavelength • Pigment – light absorbing molecule • Photoexcitation – photon energy is used to excite an electron Slide 8 Chlorophyll Slide 9 Photosystems • Combination of chlorophyll molecules, accessory pigments, and associated proteins (all arranged into a functional unit) • Localized to thylakoid or bacterial membranes Slide 10 Slide 11 Slide 12 Slide 13 Summary of Photosystems • Electrons move from water to NADPH • Called non-cyclic electron flow • 4 photons absorbed in PSII, 4 in PSI, 8 total • 2 NADPH molecules generated • 12 protons pumped Slide 14 ATP Synthesis • Photophosphorylation • Very similar to ATP synthesis in cellular respiration • Approximately 1 ATP for every four protons Slide 15 Cyclic Electron Flow Slide 16 The Calvin Cycle • Named after Melvin Calvin • Won a Nobel prize in 1961 • Elucidated through the use of radiolabeled isotopes • Occurs in the stroma of chloroplasts • Split into 3 stages: • Carboxylation of Ribulose-1,5-Bisphosphate • Reduction of 3-phosphoglycerate • Regeneration of acceptor molecule Slide 17 Slide 18 Slide 19 Carbohydrate Synthesis Slide 20 The Glycolate Pathway • Remember: Rubisco normally has carboxylase activity • It also has oxygenase activity • Produces 2 carbon molecule: phosphoglycolate • Phosphoglycolate cannot be used in Calvin Cycle • Why would evolution favor this? • How do plants deal with it? Slide 21 Slide 22 C4 Plants • Carbon is fixed into 4 carbon molecule instead of 3 • Plants adapted to hot, arid environments with lots of sunshine (tropical grasses, maize, sugarcane, etc) • Strategy: Isolate rubisco in cells that have high CO2 levels Slide 23 Slide 24 The HatchSlack Cycle Slide 25 CAM plants • Crassulacean Acid Metabolism • Cacti, succulents, orchids, etc. (where water is limited) • Strategy: Segregate reactions by time (rather than space as in C4 plants) • Only open stomata at night