photosynthesis 5 the light dependent reaction

The Light Dependent Reaction

(h) state that the light-dependent stage takes place in thylakoid membranes and that the light-independent stage takes place in the

stroma;(i) outline how light energy is converted to chemical energy (ATP and

reduced NADP) in the light-dependent stage (referenceshould be made to cyclic and non-cyclic photophosphorylation, but no

biochemical detail is required);(j) explain the role of water in the light dependent stage;

Photosynthetic electron-transfer

reactions in thylakoid

membrane

ATP NADPH

Carbon-fixation reactions in

stroma

Sugars, amino acids and fatty

acids

Water

Carbon dioxide

Oxygen

+

ChloroplastCytosol

LDR

LIR

Non-cyclic and Cyclic Photophosphorylation

• http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter39/cyclic_and_noncyclic_photophosphorylation.html

• Need 1.5 molecules of ATP per NADPH

• Noncyclic Photophosphorylation produces both NADPH and ATP

• Chloroplasts can make ATP by Cyclic Photophosphorylation without making NADPH

Definitions

• Proton-motive force: Driving force that moves protons across a membrane as a result of an electrochemical proton gradient

• Chemiosmosis: mechanism in which a gradient of hydrogen ions across a membrane is used to drive an energy-requiring process

• Photolysis: Breakdown of molecules into smaller units via absorption of light