Microm 410: Photosynthesis Photosynthesis (Photoautotrophs) Part I: Background and Overview of Photosynthesis Hydrogen bacteria- H2 - Nitrobacter- NO2 Fig. 5.23b Microm 410: Photosynthesis Fig. 5.23c Overview of Light and Dark Reactions in Reactions involved in Photosynthesis Oxygenic Photosynthesis Light reactions or phase: Oxygenic- ATP and NAD(P)H Anoxygenic- purple primarily ATP; green- sulfur/heliobacteria can generate ATP and reducing power Dark reactions or phase: CO2 fixation Calvin Benson Cycle (C3 pathway, photosynthetic carbon cycle, reductive pentose phosphate pathway) Reverse (reductive) Krebs (TCA) cycle Hydroxypropionate pathway Microm 410: Photosynthesis Fig. 20-2 Anoxygenic Reducing power Carbon Energy e lec tro ns electrons hv Part II: Oxygenic Light Harvesting pigments and Reducing power Carbon Energy their organization e lec tro ns hv hv Fig. 20-4-3 Fig. 20-3a Cyclopentanone Cyclopentanone ring ring Phytol Phytol Chlorophyll a Bacteriochlorophyll a Microm 410: Photosynthesis Fig. 20-4 Pigment/Absorption maxima (in vivo) Bchl a (purple bacteria)/ Bacteriochlor a 805, 830–890 nm Bchl b Chlor a (purple bacteria)/ 835–850, 1020–1040 nm carotenoids Bchl c (green sulfur bacteria)/745–755 nm Bchl cs (green nonsulfur bacteria)/740nm carotenoids aNo double bond between C and Bchl d 3 C ; additional H atoms are in (green sulfur 4 bacteria)/705–740 positions C3 and C4. nm b P, Phytyl ester (C20 H39O—); F, farnesyl ester (C15 H25O—); Gg, geranylgeraniol ester (C H O—); Bchl e 10 17 S, stearyl alcohol (C H O—). (green sulfur 18 37 c bacteria)/719–726 No double bond between C3 and nm C4; an additional H atom is in position C3. Bchl g dBacteriochlorophylls c, d, and e (heliobacteria)/ consist of isomeric mixtures with 670, 788 nm the different substituents on R3 as shown. Figure 20-3b Fig. 20-9-1 I. Carotenes Isoprenoids: Diaponeurosporene β-carotene (carotenoid) Neurosporene Lycopene β-Carotene γ-Carotene Chlorobactene β-Isorenieratene Primary function: photoprotective role Isorenieratene Key Absorb in blue region of spectrum Heliobacteria Purple bacteria Green nonsulfur bacteria Purple bacteria (Chloroflexus) (in presence of air) Fig. 20.8 Green sulfur bacteria Green sulfur bacteria (brown-colored species) Microm 410: Photosynthesis Fig. 20-9-2 II. Xanthophlls Bile pigments OH-Spheroidenone Spheroidenone Spirilloxanthin cyanobacteria red algae Okenone Key Heliobacteria Purple bacteria phycobiliproteins Green nonsulfur bacteria Purple bacteria (Chloroflexus) (in presence of air) phycobilisomes Green sulfur bacteria Green sulfur bacteria (brown-colored species) Fig. 20.10 Arrangement of light-harvesting chlorophylls/bacteriochlorophylls Lets talk about their arrangement in the cell …. Fig. 20-6 Complexes of 50- Antenna pigments 300 molecules excitons Reaction center chlorophylls/bacteriochlorophylls Microm 410: Photosynthesis Chloroplast Fig. 20.5 Fig. 20.10b Chlorosome Bacterial Photosynthetic Apparatus Base plate protein heliobacteria Figure 20-7 Microm 410: Photosynthesis Purple photosynthetic bacteria e- Bacteriopheophytin one photosystem Part III: Anoxygenic photosynthesis PMF photooxidized Fig. 20.14 Organization of e- carriers in purple bacteria Electron Flow in Purple Bacteria H2---> NAD(P)H photophosphorylation hydrogenase Lactate or succinate (e-) Anoxygenic ATP synthase Photosynthesis (purple) Cyclic photophosphorylation Fig. 20.15 Fig. 20.14 Microm 410: Photosynthesis Fig. 20-18 Purple bacteria Green sulfur bacteria Heliobacteria P798* −1.25 P840* Chl a–OH –1.0 Chl a P870* BChl FeS –0.75 BPh FeS 0.5 − Fd Part IV: E0′ (V) NADH Fd −0.25 Cyt Q bc 0 Q Cyt Q 1 Cyt Oxygenic photosynthesis bc Cyt Reverse 1 c electron Cyt 553 0.25 bc1 c P798 + Cyt flow P840 553 c P870 2 +0.5 Light Light Light Oxygenic Photosynthesis Plants, algae, cyanobacteria PMF Cyclic photophosphorylation Non-cyclic photophosphorylation photolysis Fig. 20.19 Microm 410: Photosynthesis Calvin-Benson Cycle Ribulose bisphosphate carboxylase (RubisCO) Part V: Dark Reactions phosphoribulokinase CO2 Fixation Fig. 20.22 Fig. 20-24 Cell material Hexose-P Glyceraldehyde 3-P Aerobic Respiration Oxalacetate Phosphoenolpyruvate Malate Fumarate Pyruvate Succinate Ferredoxinred Succinyl-CoA Acetyl-CoA Ferredoxinred Citrate α-Ketoglutarate Net reaction: Isocitrate 3 CO2 + 12 H + 5 ATP glyceraldehyde 3-P Cell material (Acetyl-CoA) Malyl ∼ CoA Glyoxylate (Hydroxypropionyl-CoA) Succinyl ∼ CoA Net reaction: 2 CO + 6 H + 3 ATP glyoxylate (Propionyl-CoA) 2 (Methylmalonyl-CoA).