1 / 10

Chapter 15 (part 2)

Chapter 15 (part 2). Photophosphorylation. Photophosphorylation. Light-Driven ATP Synthesis Electron transfer through the proteins of the Z scheme drives the generation of a proton gradient across the thylakoid membrane

snow
Télécharger la présentation

Chapter 15 (part 2)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 15 (part 2) Photophosphorylation

  2. Photophosphorylation • Light-Driven ATP Synthesis • Electron transfer through the proteins of the Z scheme drives the generation of a proton gradient across the thylakoid membrane • Protons pumped into the lumen of the thylakoids flow back out, driving the synthesis of ATP • CF1-CFo ATP synthase is similar to the mitochondrial ATP synthase

  3. Chloroplast CF1CFo ATPase • Similar in structure to mitochondrial F1Fo ATPase • CF1 domain (ATP synthesis) extends into the stroma. • Many of the protein subunits are encoded by the chloroplast genome

  4. Chloroplast Proton Motive Force (Dp) • What contributes more to PMF, DY or DpH? • In the light DpH=3 • DY is negligible due to counter ion movement in and out of the lumen • DG for export of one mole H+ across thylakoid membrane = -17 kJ/mole • DGo’ for ATP formation = 30.5 kJ/mole • Since 12 moles of protons gives –200 kJ of energy • Experiment show that 3 ATPs are generated per mole of O2 produced

  5. Energy Balance Sheet • 8 photons (4 e-) generate 1 oxygen and 2 NADPH • Photosynthetic ETC pumps between 8 and 12 protons across thylakoid membrane to generate proton gradient (DpH ~3.5). • Photophosphorylation produces 3 ATPs per O2 produced

  6. Non-cyclic photosynthetic ETC • NADPH and ATP produced • Involves both PSI and PSII cyclic photosynthetic ETC • only ATP produced • Involves only PSI

  7. Cyclic Photosynthetic ETC • Involves only PSI • Reduced ferredoxin transfers e- to Cytobf complex which then re-reduces Plastocyanin and finally the oxidized P700 of PSI • No NADPH produce.Only ATP • Levels of NADP+ thought to regulated this process. • Low NADP+ activates cyclic ETC • Observed in vitro.

  8. Arrangement of photosystems in thylakoid membrane

  9. Arrangement of photosystems in thylakoid membrane • PSII primarily present in granal lamellae • Light harvesting antennae complexes (LHC) are also present in the granal lamellae. • Under low light conditions LHCs are closely associated with PSII, Under high light condition the 2 disassociate. • PSI and ATPase are in the stroma lamellae. • Physical separation suggest that mobile electron carrier must be involved (i.e. PQ and Plastocyanin)

More Related