Light reactions

Question 1

What takes place in cytb6f

Answer 1

Q cycle - net effect is proton trasnport

Question 2

Structure of cyt6bf

Answer 2

Homodimer form consisting of 4 subunits: cytb6 (cont. 2 b type hemes), cytf (cont. c type heme), Rieske type FeS protein (2Fe-2S cluster), subunit IV

Question 3

What is the role of cytb6f

Answer 3

Mediate electrons between PSI and PSII oxidising PQH2 and reducing PC (QH2-FeS-Cytf-PC)

Question 4

What is plastocyanin

Answer 4

Mobile 1 electron carrier that cycles between Cu+ and Cu2+ - distorted tetrahedral coord

Question 5

PSI

Answer 5

Uses light energy to generate reduced Ferredoxin - >13 subunits, monomeric in euk but trimeric in cyanobac, RC cofactors bound by 11 TM helices, homologous to PSII, P700 RC

Question 6

PSI process

Answer 6

RC contains 6 Chl, phylloquinones, 3[4Fe-4S] clusters, P700 = special pair of Chl a molecules, electron transferred down pathway via Chl to quinone to set of [4Fe-4S] clusters. Electrons transferred to Ferredoxin (soluble proteins)

Question 7

What is ferredoxin

Answer 7

1 electron carrier protein with Fe2S2 centre - very reducing

Question 8

FNR

Answer 8

Flavin nucleotide reductase - generates ATP

Question 9

FTR

Answer 9

Flavin thioredoxin reductase

Question 10

Ferredoxin-NADP+ reductase

Answer 10

NADPH binds - 2 electron carrier, Ferredoxin + FNR complex

Question 11

NADPH

Answer 11

2 electron carrier, efectively an H- (hydride) carrier, source of reductants for calvin cycle

Question 12

Why are 2 photosystems necessary

Answer 12

Plastoquinol to redcuing enough to make NAPHD

Question 13

PGLR1

Answer 13

Ferredoxin plastoquinone reductase

Question 14

How are the H+ ions moving into thylakoid counterbalanced

Answer 14

Mg2+ ions moving out

Question 15

How does ATP synthase generate ATP

Answer 15

Uses proton gradient to translocate protons out of lumen into stroma - rotating mechanism