1. The Light- Dependent Reactions of Photosynthesis

2. Photosynthesis take place in 2 phases: Light-Dependent reactions Light-Independent reactions

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

6. Photosystems  There are 2 types of photosynthetic units:  Photosystem I  Photosystem II  Photosystem I rxn center is P700  Photosystem II rxn center is P680

7. Once e- is given up from reaction center, it enters an Electron Transport System  ETC used to generate energy molecules  ATP  NADPH  2 types:  Cyclic  Non-cyclic

8. Cyclic Electron Transport  Simplest light-dependent reaction: Only involves PSI  Light energy is transferred to P700 reaction center which gives up 2 e-  e-  1 o e- receptor  ETC  P700  Chemiosmosis generates ATP by photophosphorylation

10. Noncyclic Electron Transport  Involves PSI and PSII  Produces both ATP and NADPH  P700 e-  ETC  NADP +  P680 e-  ETC (chemiosmosis)  P700  Water is split by photolysis to replace P680 e-  http://www.stolaf.edu/people/giannini/flashani mat/metabolism/photosynthesis.swf http://www.stolaf.edu/people/giannini/flashani mat/metabolism/photosynthesis.swf

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

12. Let’s Review…  Main outputs of light-dependent rxns are:  NADPH from noncyclic  ATP from cyclic & noncylic  O 2 from photolysis  http://highered.mcgraw- hill.com/sites/0072437316/student_view0 /chapter10/animations.html# http://highered.mcgraw- hill.com/sites/0072437316/student_view0 /chapter10/animations.html#