5.2 Photosynthesis Pathways

Question 1

Rubisco

Answer 1

Ribulose 1.5-buphosphate carboxylase oxygenase; a critical enzyme that acts as a catalyst for the reduction of CO2 in the Calvin cycle of photosynthesis

Question 2

Photosystem ll

Answer 2

• Absorbs 680nm light (P680)
• Light energy is used to excite/transfer an e- to the primary e- acceptor
• E- are replaced by splitting water (O2 and H2 are formed as a result)
• An e- is then transferred to Plastoquinone (PQ)

Question 3

Plastoquinone (PQ)

Answer 3

• Moves an e- to the cytochrome complex
• Also helps to move H2 atoms across membrane as it transports an e-

Question 4

Cytochrome complex/plastocyanin

Answer 4

• Accepts e- from PQ and transfers it to plastocyanin
• Plastocyanin transfers the e- to photosystem l

Question 5

Photosystem l

Answer 5

• Light energy is used to excite an e-
• This e- is then accepted by an e- acceptor
• The e- acceptor passes the e- on Ferredoxin
• Ferredoxin passes the e- onto NADP+ Reductase which helps form NADPH

Question 6

Chemiosmosis in photosynthesis

Answer 6

Proton gradient is established in 3 main ways
1) Protons are moved into the thylakoid lumen by Plastoquinone (PQ)
2) The concentration of Protons in the lumen increases as water is split to provide e- for photosystem ll
3) Removal of H2 to form NADPH in the stroma decreases the concentration of hydrogen

Question 7

Chemiosmosis in photosynthesis

Answer 7

• Establishment of a proton gradient across membrane allows protons to flow through ATP Synthase which drives ATP synthesis
• Protons flow from the thylakoid lumen into the stroma

Question 8

Role of Sunlight Energy

Answer 8

• In cell. resp. high energy e- from NADH/FADH2 are transferred to lower energy molecules to form water
• In photosynthesis e- move from low energy water to a higher energy level in NADPH
• This is accomplished through the addition of light energy which “energizes” e- to a higher energy level

Question 9

Linear e- transport

Answer 9

: When e- move thru both photosystems to form NADH
- Called linear bcuz e- move in a straight line to NADPH
- Splits water into O2, H2 ions, and free e-

Question 10

Cyclic e- transport

Answer 10

Uses photosystem l to transfer e- to plastoquinone to pump protons across membrane
- Uses ferredoxin to reduce plastoquinone
- E- move in a cycle
- Used to create the extra ATP needed in the Calvin cycle (more ATP is needed than NADPH)