Summary The Light Dependent Stage and The Calvin Cycle

Enzyme in thylakoid is activated by
light & splits water (photolysis):
LIGHT DEPENDENT STAGE: H2O  2H+ + 2e- + ½ O2
The 2 ELECTRONS replace those
Photon lost by PSII.



Photosystem II in the
thylakoid membrane
Photosystem I in the
2 ELECTRONS in the thylakoid membrane
photosystem absorb energy
2 ELECTRONS absorb the
from photon. They become
energy from a photon. They
excited & are picked up by
become excited & are
an electron carrier.
picked up by an electron
carrier.


The electron carrier carries them down the
electron carrier chain. The ELECTRON loses Electron carrier carries them
energy as it passes down the chain & this down the electron carrier chain.
energy causes H+ ions to be actively The ELECTRON loses energy as it
transported into the thylakoid. passes down the chain & this
energy is used….
The 2 ELECTRONS replace ones lost at PSI.




A steep H+ ion gradient is now created (more
H+ ions inside the thylakoid than in the
stroma). This causes them to diffuse out of the
thylakoid through protein channels associated
with ATP synthase.



The energy provided by this is … with the ELECTRONS and
used to: the H+ ions from photolysis
ADP + Pi  ATP ½ O2 to produce reduced NADP.

This happens when 3H+ ions move
through.