BIBC102.SU05 Lecture 10 August 22, 2005 PHOTOSYNTHESIS

% points F ( 60 pts) C (>72 pts) B (>86 pts) A (>102 pts) MIDTERM

PHOTOSYNTHESIS LNC Chapter 19 Section 19.6

LNC Fig

LNC Fig

LNC Fig

The Light Reactions Photophosphorylation

LNC Fig

The Physics of Light Absorption : E = h = hc/ h = Planck’s constant (6.626 x J.sec) c = speed of light (2.998 x 10 8 m/sec in vacuum) = wavelength ( nm for visible region) 1 mole of photons (1 Einstein) with = 700 nm has the energy of 171 kJ

CHLOROPHYLL LNC 19-40a

PHYCOERYTHROBILIN LNC 19-40b

 -CAROTENE LNC 19-40c

Nature 416, (2002) Coprophagy: An unusual source of essential carotenoids J. J. NEGRO*, J. M. GRANDE*, J. L. TELLA*, J. GARRIDO†, D. HORNERO†, J. A. DONÁZAR*, J. A. SANCHEZ-ZAPATA‡, J. R. BENÍTEZ§ & M. BARCELL§ * Department of Applied Biology, Estación Biológica de Doñana, CSIC, Pabellón del Perú, Avda María Luisa, s/n Seville, Spain † Food Biotechnology Department, Instituto de la Grasa, CSIC, Avda Padre García Tejero 4, Seville, Spain ‡ Area de Ecología, Departamento de Biología Aplicada, Universidad Miguel Hernández, Alicante, Spain § Zoo de Jerez, Taxdirt s/n Jerez de la Frontera, Spain The rare Egyptian vulture (Neophron percnopterus) stands out among the Old World vultures (Family Accipitridae ) because of its brightly ornamented head, which is coloured yellow by carotenoid pigments, and its practice of feeding on faeces. Here we show that Egyptian vultures obtain these pigments from the excrement of ungulates. To our knowledge,

LUTEIN (XANTHOPHYLL) LNC 19-40d

LNC 19-41

LNC 19-44

Fate of a photon absorbed by a molecule: 1. Internal conversion : kinetic energy; rotations and vibrations 2. Fluorescence : a photon is re-emitted, but at longer  3. Exciton transfer : resonance energy transfer from one molecule to another nearby molecule 4. Photooxidation : the excited molecule actually loses an electron to form a cationic free radical the free radical becomes a strong oxidizing agent

LNC Fig A light-harvesting complex with 7 chlorophyll a, 5 chlorophyll b and 2 lutein molecules (a monomer is shown) the functional unit of a LHC is a trimer

LNC Exciton transfer Photo- oxidation

LNC 19-51b A trimeric photosystem I viewed from the thylakoid lumen perpendicular to the membrane

LNC 19-51c Photosystem I (monomer) with antenna chlorophylls and carotenoids Reaction center

LNC 19-49

pheophytin plastoquinone mobile quinone Cyt b 6 f complex Plastocyanin (Cu) special acceptor chlorophyll phylloquinone iron-sulfur center Ferredoxin ([Fe-S] flavoprotein- ferredoxin NADP+ oxidoreductase

PHYLLOQUINONE = A 1 (in previous Figure) redox center hydrophobic membrane anchor

LNC 19-51a Photosystem I F X, F A, F B and ferredoxin are [Fe-S] proteins From PHOTOSYSTEM II NADP +

From: A. Zouni et al. Nature 409, (2001) Structure of Photosystem II of Synechococcus elongatus

LNC 19-56

LNC 19-49

LNC 19-54b The cytochrome b 6 f complex

LNC 19-54c The cytochrome b 6 f complex To reaction center of PS I

LNC 19-57

LNC 19-53

LNC 19-52

cyclic photophosphorylation No oxygen produced No NADP+ reduced ATP is synthesized

bacteriorhodopsin LNC Fig

LNC Fig b

2 H 2 O + 2 NADP +  O NADPH + 2H + ½ O H + + 2e -  H 2 OE’ o = volts NADP + + H + + 2e -  NADPHE’ o = volts  G’ o = - 2 x 96.5 kJ/Vmol x (-1.240volts) = kJ/mol i.e. we need 2 x 239 kJ to make 2 moles of NADPH One mole of photons has ~180 kJ/Einstein From 8 moles of photons we get ~ 1440 kJ We also pump protons to set up a protonmotive force that can be used to make ATP From measurements: we make ~ 3 moles ATP per mole of O 2 produced

End of lecture 10 Aug. 22, 2005