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Photosynthesis Chapter 10

Photosynthesis Chapter 10. Photosynthesis. P rocess that converts solar energy into chemical energy Directly or indirectly, photosynthesis food for almost the entire living world. Photosynthesis.

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Photosynthesis Chapter 10

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  1. PhotosynthesisChapter 10

  2. Photosynthesis • Process that converts solar energy into chemical energy • Directly or indirectly, photosynthesis food for almost the entire living world

  3. Photosynthesis Photosynthesis is a complex series of reactions that can be summarized as the following equation: 6 CO2 + 12 H2O + Light energy  C6H12O6 + 6 O2 + 6 H2O

  4. Autotrophs= produce own food • Autotrophs are the producers of the biosphere, producing organic molecules from CO2 and other inorganic molecules • Almost all plants are photoautotrophs • Uses the energy of sunlight to make organic molecules

  5. Photosynthesis • Initial Source of Energy for Most Systems • Primary Producers= source of organic molecules for most other organisms • Terrestrial Systems= Plants • Aquatic Systems= Phytoplankton • Consumers= heterotrophs= consume organic material from other organisms • Cellular Respiration Primary Producers Consumers Decomposers

  6. Photosynthesis • Plants use ~50% of sugars produced for cellular respiration to fuel own cellular processes • Rest of sugar is used as building blocks for other organic molecules • Ultimately, consumed by heterotrophs and used for cellular respiration

  7. Figure 10.2 (b) Multicellularalga (c) Unicellularprotists (e) Purple sulfurbacteria Primary Producers: plants, algae, protists, and some prokaryotes (a) Plants These organisms feed not only themselves but also most of the living world. (d) Cyanobacteria 40 m 10 m 1 m

  8. Consumers • Heterotrophs are the consumers of the biosphere • Heterotrophs= obtain organic material from other organisms • Almost all heterotrophs, including humans, depend on photoautotrophs for food and O2

  9. Humans rely on primary producers for other types of fuel • The Earth’s supply of fossil fuels was formed from the remains of organisms that died hundreds of millions of years ago • In a sense, fossil fuels represent stores of solar energy from the distant past • Biofuels

  10. Chloroplasts • Energy-producing organelle in plants • Converts solar energy into chemical energy • Contains green pigment known as chlorophyll • Light absorbing pigment • Gives leaves the green color • All green parts of plant have chloroplasts • Chloroplasts are found mainly in cells of the mesophyll, the interior tissue of the leaf • Cells can have 30-40 chloroplasts

  11. Figure 10.4a Leaf cross section Chloroplasts Vein Mesophyll Stomata CO2 O2 Chloroplast Mesophyllcell 20 m

  12. Figure 10.4b Chloroplast Outermembrane Thylakoid Intermembranespace Granum Stroma Thylakoidspace Innermembrane 1 m

  13. Photosynthesis • Photosynthesis is a complex series of reactions that can be summarized as the following equation: 6 CO2 + 12 H2O + Light energy  C6H12O6 + 6 O2 + 6 H2O • Chloroplasts split H2O into hydrogen and oxygen, incorporating the electrons of hydrogen into sugar molecules and releasing oxygen as a by-product

  14. Figure 10.5 Photosynthesis Reactants: 6 CO2 12 H2O 6 H2O Products: C6H12O6 6 O2

  15. Photosynthesis • Endergonic reaction • Sunlight • Energy stored in bonds of glucose • Redox Reaction • Photosynthesis reverses the direction of electron flow compared to respiration • Oxidation= loss of electrons • Water is oxidized • Reduction= gain of electrons • Carbon dioxide is reduced

  16. Figure 10.UN01 Photosynthesis becomes reduced C6 H12 O6 6 O2 Energy  6 CO2  6 H2O becomes oxidized

  17. Photosynthesis occurs in 2 stages • Light Reactions (“photo) • Occurs in thylakoids • Split H2O • Release O2 • Reduce NADP+ to NADPH • Generate ATP from ADP by photophosphorylation

  18. Figure 10.6-1 H2O Light NADP ADP +P i LightReactions Chloroplast

  19. Figure 10.6-2 H2O Light NADP ADP +P i LightReactions ATP NADPH Chloroplast O2

  20. Photosynthesis occurs in 2 stages • Dark Reactions: Calvin Cycle (“synthesis”) • Occurs in the stroma • Uses ATP and NADPH from light reaction to reduce CO2 and produce sugars • Begins with carbon fixation, incorporating CO2 into organic molecules

  21. Figure 10.6-3 CO2 H2O Light NADP ADP +P i CalvinCycle LightReactions ATP NADPH Chloroplast O2

  22. Figure 10.6-4 CO2 H2O Light NADP ADP +P i CalvinCycle LightReactions ATP NADPH Chloroplast [CH2O](sugar) O2

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