Light dependent

Step 1

H2O is broken down into protons, electrons, and oxygen using **enzyme z**

* electrons go onto **PS2**
* Oxygen is released as waste
* hydrogen contributes to the concentration gradient

Step 2

Electrons are passed onto PS2

* Photons hit the protein which excites the electrons
* energy is passed onto ps2s reaction centre, **P680**

Step 3

* electrons from p680 are excited and passed onto **PQ**
* PQ then passes the electrons to the **b6f complex**
* electrons signal for b6f to open which pumps protons from the **stroma to the lumen**
* conc gradient causes the protons to diffuse back into the stroma through the ATP synthase,
* this is **Photophosphorylation**

Step 4

* electrons are passed from b6f to **PC**, which passes them to PS1
* light is absorbed by the pigment in ps1 and the energy excites electrons in the reaction cemtre **P700**

step 5

* electrons are now transfered to **Fd (ferredoxin)**

Step 6 option a (non cyclic)

* electrons from ferredoxin is used to reduce NADP+ to NADPH
* NADPH is then used in the calvin cycle

step 6 option b (cyclic)

* electrons from ferredoxin is transferred back to cytochrome b6f complex
* causes a cyclic reaction