Question

Question:The ultimate electron acceptor in the respiration process

is molecular oxygen. Electron transfer through the respiratory chain takes place through a complex series of oxidation– reduction reactions. Some of the electron transport steps use iron-containing proteins called cytochromes.

All cytochromes transport electrons by converting the iron in the ytochromes from the 13 to the 12 oxidation state. Consider the following reduction potentials for three different cytochromes used in the transfer process of electrons to oxygen (the potentials have been corrected for pH and temperature): cytochrome a1Fe312 1 e2hcytochrome a1Fe212 % 5 0.385 V cytochrome b1Fe312 1 e2hcytochrome b1Fe212 % 5 0.030 V cytochrome c1Fe312 1 e2hcytochrome c1Fe212 % 5 0.254 V In the electron transfer series, electrons are transferred from one cytochrome to another. Using this formation, determine the cytochrome order necessary for spontaneous

transport of electrons from one cytochrome to another,

which eventually will lead to electron transfer to O2.

Short answer

Answer:

Cytochrome b < cytochrome c < cytochrome a

Step-by-step solution

analyzing the given data

cytochrome a(Fe³⁺) + e^-—› cytochrome a(Fe²⁺)

E° = 0.385V

cytochrome b(Fe³⁺) + e^-—› cytochrome b(Fe²⁺)

E° = 0.03 V

cytochrome c(Fe³⁺) + e^-—› cytochrome c(Fe²⁺)

E° = 0.254 V

arranging the cytochromes in the order necessary for spontaneous transport of electrons

We know that the transport of e^- happens due to the increase in reduction potential.Arranging the cytochromes in the increasing order of their reduction potential, we get:

0.03 V < 0.254 V < 0.385 V

Cytochrome b < cytochrome c < cytochrome a