Cell Biology Chapter 11 Part 1

Question 1

Photosystem II complex

Answer 1

Oxidization of 2 H2O water, evolving O2; 4 H+ into the thylakoid lumen for ATP synthesis; Passes excited e- to plastoquinone (PQ)

Question 2

Cytochrome b6/f complex

Answer 2

Accepts electrons from plastoquinone (noncyclic) or ferredoxin (cyclic); Pumps protons unidirectionally into thylakoid lumen; Mixing the cycle of PQ and the pumping of Cb6/f complex,
4H+ go into the thylakoid lumen

Question 3

Photosystem I complex

Answer 3

P700 becomes photoexcited, enabling it to reduce ferredoxin (stromal protein); The 2 e- coming from PSII are excited again and passes to ferredoxin

Question 4

Ferredoxin-NADP+ reductase

Answer 4

Enzyme on stromal side of thylakoid membrane
o Ferredoxin passes the 2e- to Ferredoxin-NADP + reductase; Ferredoxin-NADP reductase uses those electrons and NADP+ + H+ (from the stroma) to create NADPH (reduction); NADPH can be used for the Calvin Cycle to create glucose

Question 5

ATP synthase complex

Answer 5

Uses energy from exergonic flow of protons from the thylakoid lumen to synthesize ATP in the stroma; ATP is essential for carbon fixation/assimilation (Calvin Cycle)

Question 6

Overall Light Reaction + Photophosphorylation

Answer 6

2 H20 + 2 NADP+ - - - (8 photons) - - - > O2 + 2 NADPH (stroma) + proton gradient (lumen); The proton gradient is used to create ATP ; 4H+ (lumen) + ADP + Pi = 1 ATP in the stroma; 8 photons yields ~ 3 ATP and 2 NADPH; The NADPH and ATP feed into the Calvin Cycle

Question 7

Review of Light Independent Reactions:

Answer 7

Producing sugars from CO2 and water: Uses energy produced during light-dependent reactions (ATP and NADPH); Occurs in the stroma; Initial step catalyzed by Rubisco; Slow acting enzyme, not very efficient; Attaches CO2 to a 5 carbon sugar (ribulose 1,5-bisphosphate) to create 6 carbon intermediate