11.2 light-dependent reactions

Question 1

what 2 products are light-dependent reactions?

Answer 1

• ATP
• O2

Question 2

how is ATP made in the light-dependent reaction? (4)

Answer 2

1) - 2e- becomes excited by light & is passed on e- carriers (in thylakoid membranes)
- photoionisation (chlorophyll is ionised & oxidised & e- carrier is reduced)
2) - e- passed on by oxidation-reduction reactions & loses energy at each level to e- carriers
3) - H+ ions are pumped by hydrogen pumps (with gained energy to 2e-)
4) H+ could only leave the thylakoid (down conc. gradient) by ATP synthase which synthesises ADP + Pi -> ATP

Question 3

what is photoionisation?

Answer 3

1- chlorophyll absorbs light
2- electrons are lost / chlorophyll becomes positively charged

Question 4

how is NADP reduced?

Answer 4

H+ that passed through ATP synthases are taken up by NADP+ & 2e- from (1 & 2) -> reduced NADP

Question 5

how is photolysis of water carried out?

Answer 5

H2O molecules are split by light:
2 H2O -> 4H+ + 4e- + O2

Question 6

which product of water photolysis is used to reduce chlorophyll?

Answer 6

e-

Question 7

what are the 4 structural adaptations in the chloroplast?

Answer 7

1) impermeable - H+ gradient used by ATP synthase
2) chlorophyll - network of proteins hold it precisely to maximise light absorption
3) DNA & ribosomes - quickly make proteins
4) thylakoid membrane - large SA for attaching chlorophyll, e- carriers & enzymes