photosynthesis 8.3 Flashcards
explain light dependent reactions
Where: thylakoid space (membrane)
Aim: convert chemical energy into ATP and NADPH for Calvin cycle
1. Photoactivation: sunlight hits PS2 and excites e- in PS2.
2. that e- moves through ETC(electron transport chain) releasing enegry as they do.
3. H+ ions use this energy released to move to the thylakoid space.
4. e- stay in PS1 as they have lost all energy.
5. photolysis occurs in thylakoid space to ressource e- in PS2.
8. photoexcitation again e- in PS1 through ETC -> e- dropped into stroma
6. Chemiosmosis: H+ down concentration gradient through ATP synthase to stroma.
7. reduction reaction of ADP found in stroma into ATP using H+ energy.
9. Reduction of NADP+ using H+ and e- to form NADPH
distinguish between photosystem 1 and 2
Photosystem I is sensitive to light wavelengths of 700 nm, while Photosystem II is sensitive to light wavelengths of 680 nm.
Outline process of photoactivation of the reaction center chlorophyll.
The chlorophyll molecules in Photosystem II become activated by the photons (photoactivation) of light and pass on their activation energy to the reaction centre, which in turn passes two excited electrons to the primary electron acceptor. This then passes the two electrons to plastoquinone, a hydrophobic electron carrier, which stays inside the thylakoid membrane to pass on the electrons to the next electron carrier; continuing all the way to photosystem I .
Draw a cross section of the thylakoid membrane to show the path of transfer of excited electrons, inclusive of Photosystem II, ATP synthase, an electron transport chain (with Pq first) and Photosystem II.
see notion
explain the light independent reactions
Where: in stroma
1. RuBP is carboxylated by CO2, forming 2 x 3-carbon molecules called 3PGA, using the enzyme rubisco.
- ATP (from the light dependent reaction) activates 3PGA and provides the energy for NADPH (from the light dependent reaction) to reduce 3PGA, forming a three carbon carbohydrate, triose phosphate. (G3P)
- out of the 6 G3P, 5 of them must be reused to regenerate RuBP. 3 ATP is also needed.
Draw and label a diagram of the chloroplast.
see notion
