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Photosynthesis

Photosynthesis. 6 CO 2 + 12 H 2 O  C 6 H 12 O 6 + 6 O 2 + 6 H 2 O. Light-Dependent Reactions Light captured ATP and NADPH produced H 2 O is split O 2 is released. Light-Independent Reactions ATP and NADPH in CO 2 in Carbohydrates produced. Overview of Photosynthesis.

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Photosynthesis

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  1. Photosynthesis 6 CO2 + 12 H2O  C6H12O6 + 6 O2 + 6 H2O

  2. Light-Dependent Reactions Light captured ATP and NADPH produced H2O is split O2 is released Light-Independent Reactions ATP and NADPH in CO2 in Carbohydrates produced Overview of Photosynthesis

  3. Light-Dependent Reactions • Take place in the thylakoid membranes • Light is absorbed by chlorophyll a and/or accessory pigments • These pigments are attached to pigment-binding proteins and arranged in an antenna system

  4. When energy absorbed the energy is passed from one pigment molecule to another • Energy absorbed by pigments is transferred to a reaction center • pair of cholorophyll a molecules • the reaction center e- moves to a higher energy level • This e- is transferred to primary e- receptor

  5. Photosystems • There are 2 types of photosynthetic units: • Photosystem I • Photosystem II • Photosytem I rxn center is P700 • Photosytem II rxn center is P680

  6. Cyclic Electron Transport • Simplest light-dependent reaction • Only involves PSI • Light energy is transferred to P700 reaction center which gives up 2 e- • e- reduces primary e- receptor

  7. From primary e- receptor, e- enters ETC • As e- pass down ETC, H+ are pumped across membrane into lumen of thylakoid • ATP is generated by chemiosmosis • Photophosphorylation • e- is channeled back to reaction center from which it was lost

  8. Noncyclic Electron Transport • Involves PSI and PSII • Produces both ATP and NADPH • PSI absorbs energy & passes e- to ETC • End of this ETC the e- reduces NADP+ in presence of enzyme

  9. PSII becomes activated and gives off e- from P680 • E- goes to primary e- receptor and down ETC to PSI to replace its lost e- • As e- moves from PSII to PSI, H+ are pumped across membrane • E- lost from PSII are replaced by photolysis • Splitting of H2O into 2 H+, 2 e- and oxygen http://www.stolaf.edu/people/giannini/flashanimat/metabolism/photosynthesis.swf

  10. http://www.cst.cmich.edu/users/baile1re/bio101fall/enzphoto/photoanima.htm#http://www.cst.cmich.edu/users/baile1re/bio101fall/enzphoto/photoanima.htm#

  11. Let’s Review… • Main outputs of light-dependent rxns are: • NADPH (from noncyclic electron transport) • ATP (from cyclic and noncylic transport) • O2 – from photolysis • http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter10/animations.html#

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