Metabolism - Johnson

Question 1

name and describe the 5 subunits of ATP synthase

Answer 1

• A-subunit: - Proton half channels connect each side of the membrane to the c-subunits proton binding glutamate residues
• B2 and δ-subunits - Form the ‘stator’ bridging the F1 and Fo domains and ensuring the two parts remain coupled
• 3 α-subunits and 3 β-subunits - Form the F1 head α and β are similar but only β units are catalytically active with α playing structural role
• 8-15c subunits - Act as the proton driven rotor embedded in the membrane
• γ-subunit - The central stalk that transmits torque from Fo to F1 changing the conformation of the α-subunits between three states O, L and T

Question 2

how many protons are released per NADH oxidised in mitochondria? what is the H+/e- ratio?

Answer 2

10H+ per NADH

H+/e- = 5

Question 3

how many protons are released per NADP+ reduced in chloroplasts? what is the H+/e- ratio?

Answer 3

6H+ per NAPD+ reduced

H+/e- = 3

Question 4

what happens at PSII

Answer 4

photolysis of H2O

2PQ is reduced to 2PQH2 by accepting 4H+ and 4e- from 2H2O, 4H+ pumped from the stroma to lumen

Question 5

How many LHCII’s are there is PSII

Answer 5

PSII is dimeric (2xRC)
2 monomeric LHCIIs per RC
2 trimeric LHCII per RC

Question 6

name 9 key cofactors found in PSII RC

Answer 6

Mn cluster
Chlorophyll a
tyrosine161
Chlorophyll aA
Chlorophyll aB
pheophytin A
pheophytin B
plastoquinone A
plastoquinone B

(large letter depicting which arm the molecule is located on)

Question 7

what is the function of PSI, give an equation

Answer 7

PSI functions as a plastocyanin-ferredoxin oxidoreductase (ie it oxidises plastocyanin and reduced ferredoxin)
2PCred+2Fdox—>2PCox+2Fdred

Question 8

name 10 key cofactors found in PSI RC

Answer 8

chlorophyll a
chlorophyll aA1
chlorophyll aA2
phylloquinone QKa
Iron-Sulphur clusters - Fx
Iron-Sulphur clusters -Fa
Iron-Sulphur clusters -Fb
Phylloquinone QKb
chlorophyll aB2
chlorophyll aB1

Question 9

what does FNR catalyse? give an equation

Answer 9

catalyses the reduction of NADP+ by electrons from Fdred and 1H+ from the stroma
2Fdred per 2H2O molecules

Question 10

what happens at cyt b6f?

Answer 10

per every PQH2 2H+ are PUMPED from the stroma, and 2H+ are released from PQH2
therefore, for every H2O molecule there are 4H+ released/pumped into the lumen
2PQH2+2PCox+4H+n —> QH2+Q+2PCred+8H+