Chloroplasts

reaction type 1 - light photons

photons hit chlorophyll molecule, energy from light elevates electrons to higher energy state

reaction type 1 - electrons in thylakoid membrane

primary electron acceptor traps the high energy electron before it drops back down - transferred to adjacent chlorophyll, repeats until it reaches a reaction centre - excites a pair of electrons with go to an electron transfer molecule and move down ETC

PS1

absorbs light best at 700nm, can't split water, P700

PS2

680nm, splits water, P680

ATP synthesis

H+ gradient established across thylakoid membrane, water is split in thylakoid space, ATP synthase uses H+ gradient for chemiosmosis

non-cyclic electron flow

uses PS1 and 2 - PS2 splits water, generates O2 and H+, electrons replace those lost by P680

cyclic electron flow

only uses PS1, electrons passed from primary acceptor through to P700, ATP synthesised as usual, no NADPH or O2 produced

reaction type 2 - dark

requires ATP and NADPH - carbon fixation by rubisco - uses 9 ATP and 6 NADPH per cycle - produces G3P and RuBP to regenerate rubisco