Lecture8

Lecture8 - Review Light reactions occur in thylakoids Light...

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1 Review Light reactions occur in thylakoids Light energy absorbed by pigments in antenna complexes Antenna complexes act as energetic funnel toward reaction center Absorption spectra reflect chemical structure of pigments Light energy converted to chemical energy via chemiosmotic mechanism Photon excites pigment -> e- transfer via ETS generates H+ gradient across membrane -> drives ATP synthesis Capacity to use water as ultimate electron donor permits final transfer of electron to NADP+ Light reactions occur in thylakoids, but ATP and NADPH produced in stroma Water splitting produces O 2 (a useful byproduct for us!) Thylakoid interior (pH ~5) Stroma (pH ~8) “Dark reactions” of photosynthesis •Light independent ( in vitro ), always occur in light ( in vivo ) •Incorporate CO 2 into sugars •Use chemical energy (ATP) and reducing power (NADPH) produced in light reactions •Two major pathways of C fixation: C3 and C4 •C3 = Calvin-Benson cycle 3 main parts to Calvin cycle: 1) carboxylation 2) reduction and sugar production 3) regenerate RuBP (“sugar shuffle”) Total cycle: consumes 3 ATP and 2 NADPH per CO 2 fixed Only 1 C fixed per turn; need 6 turns to fix enough C for entire sugar Strategy used to decipher pathway •Feed algae *CO 2 •Kill cells at different time points •Separate and identify metabolites by 2-D chromotography and
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This note was uploaded on 04/07/2008 for the course MCDB 1B taught by Professor Weimbs during the Winter '08 term at UCSB.

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Lecture8 - Review Light reactions occur in thylakoids Light...

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