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Chapter 10 Photosynthesis

Chapter 10 Photosynthesis. LE 10-2. Plants. Unicellular protist. 10 µm. Purple sulfur bacteria. 1.5 µm. Multicellular algae. Cyanobacteria. 40 µm. Leaf cross section. Vein. Mesophyll. Stomata. O 2. CO 2. LE 10-3. Mesophyll cell. Chloroplast. 5 µm. Outer membrane. Thylakoid.

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Chapter 10 Photosynthesis

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  1. Chapter 10 Photosynthesis

  2. LE 10-2 Plants Unicellular protist 10 µm Purple sulfur bacteria 1.5 µm Multicellular algae Cyanobacteria 40 µm

  3. Leaf cross section Vein Mesophyll Stomata O2 CO2 LE 10-3 Mesophyll cell Chloroplast 5 µm Outer membrane Thylakoid Intermembrane space Thylakoid space Stroma Granum Innermembrane 1 µm

  4. LE 10-4 12 H2O 6 CO2 Reactants: 6 O2 6 H2O C6H12O6 Products:

  5. H2O LE 10-5_1 Light LIGHT REACTIONS Chloroplast

  6. H2O LE 10-5_2 Light LIGHT REACTIONS ATP NADPH Chloroplast O2

  7. H2O CO2 LE 10-5_3 Light NADP+ ADP + P i CALVIN CYCLE LIGHT REACTIONS ATP NADPH Chloroplast [CH2O] (sugar) O2

  8. Light Reflected light Chloroplast LE 10-7 Absorbed light Granum Transmitted light

  9. Refracting prism White light Photoelectric tube Chlorophyll solution Galvanometer LE 10-8a 0 100 The high transmittance (low absorption) reading indicates that chlorophyll absorbs very little green light. Green light Slit moves to pass light of selected wavelength

  10. White light Chlorophyll solution Photoelectric tube Refracting prism LE 10-8b 0 100 The low transmittance (high absorption) reading indicates that chlorophyll absorbs most blue light. Slit moves to pass light of selected wavelength Blue light

  11. Chlorophyll a Chlorophyll b LE 10-9a Carotenoids Absorption of light by chloroplast pigments 400 700 500 600 Wavelength of light (nm) Absorption spectra

  12. in chlorophyll a CH3 in chlorophyll b CHO Porphyrin ring: light-absorbing “head” of molecule; note magnesium atom at center LE 10-10 Hydrocarbon tail: interacts with hydrophobic regions of proteins inside thylakoid membranes of chloroplasts; H atoms not shown

  13. Excited state e– LE 10-11 Heat Energy of electron Photon (fluorescence) Photon Ground state Chlorophyll molecule Fluorescence Excitation of isolated chlorophyll molecule

  14. Thylakoid Photosystem STROMA Photon Light-harvesting complexes Reaction center Primary electron acceptor LE 10-12 e– Thylakoid membrane Special chlorophyll a molecules Pigment molecules Transfer of energy THYLAKOID SPACE (INTERIOR OF THYLAKOID)

  15. H2O CO2 Light NADP+ ADP CALVIN CYCLE LIGHT REACTIONS ATP NADPH O2 [CH2O] (sugar) LE 10-13_1 Primary acceptor e– Energy of electrons Light P680 Photosystem II (PS II)

  16. H2O CO2 Light NADP+ ADP CALVIN CYCLE LIGHT REACTIONS ATP NADPH O2 [CH2O] (sugar) LE 10-13_2 Primary acceptor e– H2O 2 H+ + O2 1/2 e– e– Energy of electrons Light P680 Photosystem II (PS II)

  17. H2O CO2 Light NADP+ ADP CALVIN CYCLE LIGHT REACTIONS ATP NADPH O2 [CH2O] (sugar) LE 10-13_3 Primary acceptor Electron transport chain Pq e– H2O Cytochrome complex 2 H+ + O2 1/2 Pc e– e– Energy of electrons Light P680 ATP Photosystem II (PS II)

  18. H2O CO2 Light NADP+ ADP CALVIN CYCLE LIGHT REACTIONS ATP NADPH O2 [CH2O] (sugar) LE 10-13_4 Primary acceptor Primary acceptor Electron transport chain e– Pq e– H2O Cytochrome complex 2 H+ + O2 1/2 Pc e– P700 e– Energy of electrons Light P680 Light ATP Photosystem I (PS I) Photosystem II (PS II)

  19. H2O CO2 Light NADP+ ADP CALVIN CYCLE LIGHT REACTIONS ATP NADPH Electron Transport chain LE 10-13_5 O2 [CH2O] (sugar) Primary acceptor Primary acceptor Electron transport chain Fd e– Pq e– e– e– NADP+ H2O Cytochrome complex 2 H+ + 2 H+ NADP+ reductase + NADPH O2 1/2 Pc e– + H+ P700 Energy of electrons e– Light P680 Light ATP Photosystem I (PS I) Photosystem II (PS II)

  20. Mitochondrion Chloroplast LE 10-16 CHLOROPLAST STRUCTURE MITOCHONDRION STRUCTURE Diffusion H+ Thylakoid space Intermembrane space Electron transport chain Membrane ATP synthase Key Stroma Matrix Higher [H+] Lower [H+] ADP + P i ATP H+

  21. H2O CO2 Light NADP+ ADP CALVIN CYCLE LIGHT REACTIONS ATP NADPH O2 [CH2O] (sugar) STROMA (Low H+ concentration) LE 10-17 Cytochrome complex Photosystem I Photosystem II Light NADP+ reductase Light 2 H+ NADP+ + 2H+ Fd NADPH + H+ Pq Pc H2O O2 1/2 THYLAKOID SPACE (High H+ concentration) 2 H+ +2 H+ To Calvin cycle Thylakoid membrane ATP synthase STROMA (Low H+ concentration) ADP + ATP P i H+

  22. H2O CO2 Input Light (Entering one at a time) 3 NADP+ LE 10-18_1 CO2 ADP CALVIN CYCLE LIGHT REACTIONS ATP Phase 1: Carbon fixation NADPH Rubisco O2 [CH2O] (sugar) 3 P P Short-lived intermediate P 6 3 P P 3-Phosphoglycerate Ribulose bisphosphate (RuBP) 6 ATP 6 ADP CALVIN CYCLE

  23. Enzyme which fixes carbon from air ribulose bisphosphate carboxylase the most important enzyme in the world! it makes life out of air! definitely the most abundant enzyme RuBisCo It’s not easy being green! I’m green with envy!

  24. H2O CO2 Input Light (Entering one at a time) 3 NADP+ CO2 ADP CALVIN CYCLE LIGHT REACTIONS ATP Phase 1: Carbon fixation NADPH Rubisco O2 [CH2O] (sugar) 3 P P Short-lived intermediate LE 10-18_3 P 6 3 P P 3-Phosphoglycerate Ribulose bisphosphate (RuBP) 6 ATP 6 ADP 3 ADP CALVIN CYCLE 6 P P 3 ATP 1,3-Bisphosphoglycerate 6 NADPH Phase 3: Regeneration of the CO2 acceptor (RuBP) 6 NADP+ 6 P i P 5 G3P P 6 Glyceraldehyde-3-phosphate (G3P) Phase 2: Reduction 1 P G3P (a sugar) Glucose and other organic compounds Output

  25. Adaptations to hot, dry climates: • Needles, waxy coatings, not losing leaves in winter, no leaves • CAM – close stomates during day - cacti, jade, pineapple C4 –plants in hot regions with intense sunlight – sugarcane, corn. Leaves are modified so p.s. occurs in 2 different types of cells.

  26. LE 10-20 Sugarcane Pineapple CAM C4 CO2 CO2 Night Mesophyll cell CO2 incorporated into four-carbon organic acids (carbon fixation) Organic acid Organic acid Bundle- sheath cell Day CO2 CO2 Organic acids release CO2 to Calvin cycle CALVIN CYCLE CALVIN CYCLE Sugar Sugar Spatial separation of steps Temporal separation of steps

  27. Light reactions Calvin cycle H2O CO2 Light NADP+ ADP LE 10-21 + P i RuBP 3-Phosphoglycerate Photosystem II Electron transport chain Photosystem I ATP G3P Starch (storage) NADPH Amino acids Fatty acids Chloroplast O2 Sucrose (export)

  28. 1.Where did the energy come from? 2.Where did the electrons come from? 3.Where did the H2O come from? 4.Where did the O2 come from? 5.Where did the O2 go? 6.Where did the H+ come from? 7.Where did the ATP come from? 8.What will the ATP be used for? 9.Where did the NADPH come from? 10.What will the NADPH be used for? Photosynthesis summary

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