Biochem Final ETC

Question 1

ETC is how exergonic?

Answer 1

highly, ∆G^’o = -220 kJ/mol of NADH

Question 2

protein complexes of ETC

Answer 2

Complex I: NADH dehydrogenase (AKA NADH-CoQ Reductase)
Complex II: succinate dehydrogenase (Succinate CoQ reductase)
Complex III: Ubiquinone-cytochrome C oxidoreductase
Complex IV: cytochrome C, cytochrome C oxidase and ubiquinone

Question 3

E’o reduction potential

Answer 3

increases as electrons are transported down ETC
increases relative affinity for electrons in electron acceptor (oxygen)
each successive bond holds less energy due to small energy release with each pass of electron

Question 4

Complex I
net reaction

Answer 4

NADH dehydrogenase oxidation reaction
two electrons oxidized from NADH –> NAD+
H- and H+ transfer to ubiquinone - power producing, exergonic
moving 4H+ ions into intercellular space, endergonic

net rxn: NADH + 5H+ + Q –> NAD+ + QH2 + 4H+

Question 5

Complex II

Answer 5

succinate dehydrogenase couples oxidation of FADH2 to reduction of Q
FAD+ produced, reduced QH2
succinate dehydrogenase also involved in CAC
no H+ pumped

Question 6

Complex III

Answer 6

cytochrome complex c reductase oxidizes QH2 only by accepting 1 electron, the other is transferred to oxidized Q (to become new QH2)
2 H+ transferred from QH2 and 4H+ pumped into intercellular space (powered by electron transfer from QH2)

Question 7

Complex IV
net reaction

Answer 7

cytochrome complex c oxidase
oxidizes reduce cytochrome c, oxygen is end electron acceptor and grabs 2 H+ from matrix to form water
2 H+ pumped into intercellular matrix as electrons move
4 cytochrome c required to make 2 H2O

net rxn: 4cyto(red) + 8H+ (matrix) + O2 –> 4 cyto(ox) + 4H+ (inter) + 2 H2O