Two Reactions of Photosynthesis Light Reaction aka light dependent rxn Calvin Cycle aka light independent reaction Transforming light photons into ATP and the electron carrier NADPH Use ATP/NADPH to make glucose

The Light Reaction Occurs in the thylakoid membrane 2 Photosystems: I and II 2 Electron Transport Chains (ETC) Consumes H2O for protons, e- Generates O2 ATP and NADPH

e- of cholorphyll a is energized ETC donates e-, reduces NADP+ to NADPH ETC Photosystem II pigments direct energy to chlorophyll a which becomes oxidized P680/P700 refers to the wavelength of cholorphyll each best absorbs P680/p700 refer to the wavelength of chlorophyll each best absorbs. Photosystem I is energized

• H+ builds up in thylakoid Concurrently to ETC: • H+ builds up in thylakoid From H2O, proton pump • H+ diffuse from high to low concentration through ATP synthase generating ATP

Creating high proton concentration in the thylakoid Proton pump driven by e- ETC H+ Creating high proton concentration in the thylakoid P680/P700 refers to the wavelength of cholorphyll each best absorbs P680/p700 refer to the wavelength of chlorophyll each best absorbs. 2H2O oxidized 4H+ + O2 (+ e-)

Inputs & Products Radiant energy (visible wavelengths) 2H2O O2 + 4H (+ e-) At second ETC: • NADP+ + H NADPH Via chemiosmosis • ADP + ATP P

Chemiosmosis ADP + P ATP PS II PS I E T C Thylakoid Space H+ H+ ATP Synthase high H+ concentration H+ ADP + P ATP PS II PS I E T C low H+ Thylakoid Space SUN (Proton Pumping) H2O

http://www.stolaf.edu/people/giannini/flashanimat/metabolism/photosynthesis.swf http://www.science.smith.edu/departments/Biology/Bio231/ltrxn.html http://www.youtube.com/watch?v=BK_cjd6Evcw http://www.sumanasinc.com/webcontent/animations/content/harvestinglight.html

Cyclic Electron Flow P700 Primary Electron Acceptor e- ATP produced by ETC Photosystem I Accessory Pigments SUN Photons Pigments absorb light energy & excite e- of Chlorophyll a to produce ATP

Light Reaction (Electron Flow) During the light reaction, there are two possible routes for electron flow: A. Cyclic Electron Flow B. Noncyclic Electron Flow