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Photosynthesis

Photosynthesis. Ch 7. Autotrophs. Chloroplasts. Contain chlorophyll Green Site of photosynthesis Concentrated in leaves. Chloroplast Structure. Overview of Photosynthesis. Light Reaction (stage 1) Thylakoid membranes of granna Converts light energy to chemical energy

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Photosynthesis

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  1. Photosynthesis Ch 7

  2. Autotrophs

  3. Chloroplasts • Contain chlorophyll • Green • Site of photosynthesis • Concentrated in leaves

  4. Chloroplast Structure

  5. Overview of Photosynthesis • Light Reaction (stage 1) • Thylakoid membranes of granna • Converts light energy to chemical energy • O2 produced as waste product • Calvin Cycle (stage 2) • Stroma • Synthesizes sugar molecules with CO2 & energy produced in light reactions

  6. CO2 H2O Chloroplast Light NADP+ Fig. 7-5-3 ADP  P LIGHT REACTIONS CALVIN CYCLE (in stroma) (in thylakoids) ATP Electrons NADPH Sugar O2

  7. Redox (again) • Recall • Oxidation- loss of e- • Reduction- addition of e- Reduction C6H12O6 + 6 O2 6 CO2 + 6 H2O Oxidation

  8. Light Reactions Increasing energy 106 nm 10–3 nm 10–5 nm 1 nm 103 nm 1 m Gamma rays Micro- waves Radio waves UV Infrared X-rays Visible light 700 750 380 600 500 400 650 nm Wavelength (nm)

  9. Light Absorbing Pigments • Chlorophyll A • Chlorophyll B • Carotenoids

  10. Photosystems Reaction center complex Photon Light-harvesting complexes Primary electron acceptor e– Thylakoid membrane Pigment molecules Transfer of energy Pair of Chlorophyll a molecules

  11. Chlorophyll is excited Excited state e– Heat Photon Photon (fluorescence) Ground state Chlorophyll molecule

  12. Photosystems

  13. Electron transport chain Provides energy for synthesis of by chemiosmosis H+ NADPH NADP+ + Photon Photon Photosystem I ATP 6 Photosystem II Fig. 7-8a Stroma 1 Primary acceptor Primary acceptor e– 2 e– Thylakoid mem- brane 4 5 P700 P680 Thylakoid space 3 H2O H+ + 2 O2 1  2

  14. Chloroplast Stroma (low H+ concentration) Fig. 7-9 H+ H+ Light Light ADP + P ATP H+ H+ NADPH NADP+ + H+ Thylakoid membrane H+ H2O H+ H+ H+ H+ O2 + 2 H+ H+ 1  2 H+ H+ H+ ATP synthase Photosystem II Photosystem I Electron transport chain H+ Thylakoid space (high H+ concentration)

  15. Calvin Cycle CO2 ATP NADPH Input CALVIN CYCLE Output: G3P

  16. Carbon Fixation - Stomata

  17. 1 Step Carbon fixation Input: 3 CO2 Rubisco 1 Step Reduction 2 P P 3 P 6 RuBP 3-PGA 6 ATP 3 ADP 6 ADP + P 3 ATP CALVIN CYCLE Step Release of one molecule of G3P 4 2 3 NADPH 6 6 NADP+ P P 5 6 Step Regeneration of RuBP 4 G3P G3P 3 Glucose and other compounds Output: P 1 G3P

  18. Adaptations Night Mesophyll cell CO2 CO2 4-C compound 4-C compound CO2 CO2 CALVIN CYCLE CALVIN CYCLE Bundle- sheath cell 3-C sugar 3-C sugar Day CAM plant C4 plant

  19. Environmental Impacts Some heat energy escapes into space Sunlight Atmosphere Radiant heat trapped by CO2 and other gases

  20. Sunlight energy ECOSYSTEM Photosynthesis in chloroplasts Glucose CO2 + + H2O O2 Cellular respiration in mitochondria ATP (for cellular work) Heat energy 0 Photosynthesis and cellular respiration provide energy for life • Photosynthesis uses solar energy to produce glucose and O2 from CO2 and H2O • Cellular respiration makes ATP and consumes O2 during the oxidation of glucose to CO2 and H2O Figure 6.1

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