Chapter 12, Problem 12.96EP

Interpretation Introduction

Interpretation:

To determine the number of electrons that an electron carrier carries between complex III and IV per trip

Concept introduction:

Electron transport chain is a sequence of biochemical reactions in which electrons and hydrogen atoms from the citric acid cycle are transferred to various intermediate carriers and finally reacts with molecular oxygen to form a water molecule. The reaction of the formation of the water is:

  ${\text{O}}_2+4{\text{e}}^{-}+4{\text{H}}^{+}\to 2{\text{H}}_{\text{2}}\text{O}$

There are four complexes associated with the electron transport chain that is present in the inner mitochondrial membrane. The four complexes that help in the electron transfer in the electron transport chain are:

Complex I: $\text{NADH-coenzyme}\text{Q reductase}$

Complex II: $\text{Succinate-coenzyme}\text{Q reductase}$

Complex III: $\text{Coenzyme}\text{Q-cytochrome c reductase}$

Complex IV: $\text{Cytochrome c oxidase}$

Cytochrome is a protein that has a heme unit in its structure. The iron present in the heme unit participate in the redox reactions and changes its oxidation state from $+2$ to $+3$. There are various types of cytochrome depending upon protein constituents, attachments to the heme unit and the way in which the heme unit is attached to the protein. $\text{Cyt c}$ is the only water soluble cytochrome.