Question

When electron transfer is blocked, the carriers before the block become more reduced and those beyond the block become more oxidized. For each of the conditions described below, predict the state of oxidation of FMN, FAD, CoQ, cytochromes bL, bH, c1, c, a and a3, CuA and CuB.

(B) abundant NADH, but O2 exhausted

(C) abundant succinate, but O2 exhausted

(E) abundant NADH and O2, rotenone added

(F) abundant succinate and O2, rotenone added

(G) abundant succinate and O2, carboxin added

(H) abundant NADH and O2, carboxin added

Answer 1

B) All carriers reduced, in the absence of O2 the carriers are not reoxidized.

C) All the carriers reduced, in the absence of O2 and the carriers are not reoxidized. The carriers cannot reach the oxidation state.

E) Rotenone, a toxic natural product from plants,strongly inhibit NADH dehydrogenase of insect and fish mitochondria. The inhibition of NADH dehydrogenase by rotenone decreases the rate of electron flow through respiratory chain, which in turn decreases the rate of ATP production.

F) Abundant succinate which takes the pathways to TCA cycle. ATP molecule then reducing the electron carrier FAD to FADH2, and finally generating another NADH. Here, succunate is oxidized, two hydrogen atoms with their electrons are transferred to FAD, producing FADH2. The presence of rotenone make changes in the cycle with the inhibition of NADH.

G) Carboxin , which is a agricultural fungicide and also used as seed treatment agent.If the succinate is added in the presence of ATP, no reaction would have taken place.

H) Easy carriers more reduced, later carriers more oxidized.