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)