Non-Cyclic Electron Transport

Question 1

Photosystem I and II

Answer 1

Photosystem I - chlorophyll-a = P700 (absorption spectrum peaks at 700 nm)
Photosystem II - chlorophyll-a = P680 (absorption spectrum peaks at 680 nm)

Question 2

Process - Electron Transport

Answer 2

1. Photon strikes PSII, exciting electron in P680, picked up by plastoquinone (PQ) then transported to cytochrome b6-f
2. Cytochrome b6-f uses energy from electrons to pump H+ ion from stroma into lumen then passes electrons to plastocyanin (PC)
3. PC passes electrons to PSI where photon strikes electrons at P700 again to “recharge” them
4. Excited electrons pass to ferrodoxin (Fd) which passes to NADP+ reductase (FNR)
5. FNR combines electrons with NADP+ and H+ to produce NADPH

Question 3

Process - Photolysis

Answer 3

Electrons that left P680 are replaced by electrons from splitting of water molecule using enzyme “Z”, which produces electrons (that go to P680), oxygen, and H+

Question 4

Process - Chemiosmosis

Answer 4

High concentration of H+ ions in lumen results in electrochemical gradient (charge difference), storing PMF, which causes ions to travel through ATP synthase, powering synthesis of ATP from ADP + Pi