Overview of Photosynthesis importance: fix tons of CO2 per year, used as energy for virtually all organisms similarity to ETC/ox-phos, PPP and tied to gng 2 phases light-dependent rxns (light rxns) light-independent rxns (dark rxns) location: chloroplast

Detailed Chloroplast Structure Porous outer membrane, tight inner membrane Stroma thylakoid disk granum (grana) thylakoid lumen Light rxns take place on thylakoid membrane, dark rxns stroma

Light is Captured by Several Classes of Molecules Fig Light is Captured by Several Classes of Molecules Fig. 19-40(a) Lehninger POB 4th Ed. Chlorophylls

Light is Captured by Several Classes of Molecules Fig Light is Captured by Several Classes of Molecules Fig. 19-40 (b)-(d) Lehninger POB 4th Ed. Carotenoids and other conjugated compounds

Light Reactions Fig. 19-41 Lehninger POB 4th Ed. Reason for numerous molecules

Light Reactions Fig. 19-45 Lehninger POB 4th Ed. “Special Pair” Photosystems I and II

Photosystem I (P700) Fig. 19-49 Lehninger POB 4th Ed. Not confident all molecules have been ID’d Major molecules Some of the reactions which occur NADPH produced

Photosystem II (P680) Fig. 19-49 Lehninger POB 4th Ed. Major molecules ATP produced

PSI and PSII Together Form the “Z-scheme”

Photophosphorylation Fig. 19-54(c) Lehninger POB 4th Ed. Proton gradient develops as e– are transported high pH inside thylakoid lumen

Water Splitting Complex Science 292:447, 2001 PSII does not directly perform sequential one-e– transfers Rather, it has an integral inorganic catalyst from which it extracts 4 e– and then reacts with 2 H2Os to form O2 4 Mn electronically coupled as Mn4 cluster

Photophosphorylation Proton gradient develops as e– are transported high pH inside thylakoid lumen protons come out through Fo of “C-ATPase” (CFo) F1 rotor forms ATP (CF1)

Cyclic Photophosphorylation Fig. 19-49 Lehninger POB 4th Ed. P700 only NO NADPH produced, only ATP (less) Major molecules: P700, Fd, Cyt. B6, Cyt f, PC

~Idealized Balanced Net Rxn

Dark Reactions - C3 plants 3PG first molecule produced containing the fixed carbon

Dark Reactions - C3 plants 3PG first molecule produced containing the fixed carbon

Dark Reactions - C3 plants 3PG first molecule produced containing the fixed carbon

Dark Reactions – Rubisco Reaction rubisco is the most abundant protein in the world

3PG  Glucose What rxns are required?

Regeneration of Ribulose-1,5-bisphosphate

~Idealized Balanced Net Rxn

C4 Plants The Hatch-Slack Pathway Fig. 20-23 Lehninger POB 4th Ed. Molecular logic Division of labor Additional Reactions

Additional Rxns of the Hatch-Slack Pathway Fig Additional Rxns of the Hatch-Slack Pathway Fig. 20-23 Lehninger POB 4th Ed.

Regulation Occurs Several Ways Fig. 20-18 Lehninger POB 4th Ed. Regulation by light a. FBPase activated b. light-induced Mg2+ efflux to stroma c. thioredoxin 2. Rubisco Allosterism (a) carbamoylation stim (b) rib-1,5-P2 inh. Carb. (c) B overcome ATP? (d) 2-carboxyarabinitol-1-phosphate