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D
Light-dependent reactions
3.2 The `light' stage of photosynthesis: photolysis of water and photophosphorylation
The first stage, or set of reactions, involved in photosynthesis is called the light-dependent stage. The light-dependent
reactions occur in the thylakoid membranes inside chloroplasts. It is the photosystems (which are made up of many
photosynthetic…

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The Z-pathway
The series of reactions involved in the light-dependent stage are known collectively as the `Z-pathway' because of the
movement of electrons across the photosystems and thylakoid membrane.
electron
acceptor
electron
acceptor
-
ATP 2e
NADP
2e
- NADP reductase
NADPH
+
2H
-
2e ADP + Pi
ATP…

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The table below compares the different types of photophosphorylation to provide a summary:

non-cyclic photophosphorylation cyclic photophosphorylation

Which photosystems are involved? PSI and PSII PSI only

Does the reaction involve photolysis of water? yes no

Which molecule is the electron donor? water chlorophyll a (P700) in PSI

Which molecule is…

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