#5: Pathway of Photosynthesis

Question 1

1. Photosystem II –P680

Answer 1

• Oxidizes (splits) water into electrons, protons, and oxygen gas (released for us!)
• Photon of light excites P680*, releasing an electron to primary acceptor and creating P680+
• P680 is highly electronegative and water is oxidized leaving H+ and oxygen gas

Question 2

2. Cytochrome complex

Answer 2

• PQ (protein) receives electron from primary acceptor and moves to “cytochrome complex”
• Energy carried in electron moves another H+ into the thylakoid

Question 3

3. Photosystem I – P700

Answer 3

• From the cytochrome complex energy is nearly gone and a second photon is used to provide more energy
• This high energy electron is transferred along the chain and used to reduce NADP+ to NADPH (through NADP reductase)

Question 4

4. Proton Gradient

- 3 ways

Answer 4

Photosystem I, cytochrome complex (PQ), Photosystem II create a proton gradient across the thylakoid membrane in 3 ways:

1. Oxidation of water
2. Carrying protons across with PQ
3. Removal of protons from the stroma during reduction NADP+