Plastocyanin: a small, soluble-copper protein

1. Plastocyanin: a small, soluble-copper protein 1 e-

2. Q cycle 1st cycle: QH2 + PC(ox) Q•+ 2 H+ + PC(red) 2nd cycle: QH2 + Q• + PC(ox) + 2 H+ QH2 + Q+ 2 H+ + PC(red) Net reaction: QH2 + 2 PC(ox)+ 2H+  Q + 2 PC(red) + 4H+

3. Cyclic PhotosystemⅠ (cyclic photophosphorylation) Only ATP formation, neither NADPH nor O2 is generated 2ATP / 4 photons during high NADPH/NAD+ ratio

4. Herbicides:block e- flowresistance Web Topic 7.10 between ferredoxin acceptor and NADP reduced Superoxide formation, damage lipid malondialdehyde

5. Photophosphorylation:the captured light energy is used for light-dependentATP synthesis In the chloroplast  oxidative phosphorylation in the mitochondrion 1960s Mitchell: chemiosmotic mechanism Proton motive force [ △p (mv)= △E －59(pHi－pHo) ] Jagendorf (1966): an incisive experiment

6. H2O oxidation NADPH formation ATP synthesis NADH oxidation H2O formation ATP synthesis orientation

7. The protective, scavenging, and repairing mechanisms of the photosynthetic machinery Easily damage the cellular components, especially lipids. Especially for PSⅠ Def: the inhibition of potosynthesis by excess light

8. Carotenoids類胡蘿蔔素: photoprotective agents, not only as accessory pigments Photochemical quenching: the energy stored in the excited chlorophylls葉綠素is rapidly dissipated by photochemistry.  chlorophyll fluorescence  Non-photochemical quenching: the quenching of chlorophyll fluorescence by processing other than photochemistry, such as excitation transfer, heat or photoinhibition. Xanthophylls葉黃素: three carotenoids – violaxanthin, antheraxanthin, zeaxanthin, involved in nonphotochemical quenching.

9. Xanthophyll cycle: [Sapozhnikov et al., (1957) discovered] an important avenue for dissipation of excess light energy carotenoids de-epoxidase No. double bonds bind to light-harvesting antenna proteins, conformation change  quenching and heat dissipation

10. The biosynthetic pathway of chlorophyll 1. Chlorophyllase: remove phytol 2. Mg de-chelatase 3. Oxygenase: open porphyrin  Stored in vacuole

11. Chloroplast  Maternal or non-Mendelian inheritance (mitochondria)  Semiautonomous cell organelle  Chloroplast proteins are encoded by either chloroplastic or nuclear DNA chloroplast: large subunit of rubisco nucleus: small subunit of rubisco, plastocyanin (transit peptide)

12. 1. What is an absorption spectrum? What is the absorption spectrum of chlorophyll? What is the relation between the electromagnetic spectrum of solar radiation and the absorption spectrum of chlorophyll? 2. What is an action spectrum? What is the relationship between the action spectrum for photosynthesis and the absorption spectrum of chlorophyll? 3. Photosynthesis in oxygen-evolving organisms is said to involve two distinct photosystems. Describe the two photosystems and provide two lines of experimental evidence that led to their discovery. 4. What is the role of electron transport in oxygen-evolving photosynthesis? Name the final electron donor and final electron acceptor in photosynthesis. Describe the path traveled by an electron in the electron transport process. 5. How are the major pigments and proteins involved in photosynthesis organized in the thylakoid membrane? 6. Describe the process of ATP synthesis at the thylakoid membrane. Name the reactants, the energy source and the role of light in the process. Can ATP synthesis take place in thylakoid membranes kept in the dark? Explain your answer.