5.2.1 (d) the light-dependant stage Flashcards
order of photosystems
PS II THEN PS I
PS II wavelength?
680 mm
PS I wavelength?
700 nm
what happens when light is absorbed by PS II?
electrons are excited and move to a higher energy from PS II into an electron transport chain
what does the photolysis of water produce?
1/2 O2
2 e-
2 H+
what replaces the lost electrons at PS II?
the 2e- from photolysis
where does the photolysis of water occur?
in the thylakoid space
what happens to the excited electrons as they move along the electron transport chain?
they lose energy
what happens to the energy lost by electrons in the ETC?
this energy is used to pump H+ ions from the stroma into the thylakoid
generates a proton gradient with a higher conc in the thylakoid than the stroma
what do the H+ ions in the thylakoid space do?
they return down the concentration gradient into the stroma through the ATP synthase protein channel
what happens in ATP synthase?
H+ ions are returned back into the stroma
this allows for the phosphorylation of ADP to form ATP
what happens when light is absorbed by PS I?
the electrons move to a higher energy level out of the photosystem and each combine with NADP and a H+ ion to form reduced NADP
what are the 2 types of light dependant reactions?
non-cyclic photophosphorylation
cyclic photophosphorylation
what is produced in non-cyclic?
ATP
reduced NADP
what is produced in cyclic?
ATP
what happens in cyclic?
electrons from PS I are returned to PS I instead of being used to reduce NADP
this allows for the formation of ATP but not reduced NADP
