Chapter 20, Problem 1RE

RECALL Briefly summarize the steps in the electron transport chain from NADH to oxygen.

Interpretation Introduction

Interpretation:

The steps of the electron transport chain from $\text{NADH}$ to oxygen are to be summarized.

Concept introduction:

Electron transport chain is the series of electron transfer from electron donor to electron acceptor; it is a redox reaction.

It is the last component of aerobic respiration and is the only reaction that utilizes atmospheric oxygen.

Answer to Problem 1RE

Solution: Following are the steps of the electron transport chain from $\text{NADH}$ to oxygen:

$\begin{array}{ccc}\text{NADH}\to & \text{FMN}\to & \text{CoQ}\\ & & \downarrow \\ \text{cytochrome }a& \leftarrow \text{cytochrome }c& \leftarrow \text{cytochrome }b\\ \downarrow & & \\ \text{cytochrome }{a}_3\to & \text{cytochrome }a{a}_3\text{ complex}\to & \text{Oxygen}\end{array}$

Explanation of Solution

First the electrons from $\text{NADH}$ are transferred to the flavin-containing protein, flavin mononucleotide $\left(\text{FMN}\right)$, and then to coenzyme-Q. The electrons from coenzyme-Q are transferred to various cytochrome complexes, starting with cytochrome b, to cytochrome c, then to cytochrome a, followed by cytochrome $a_3$, and finally from cytochrome $a{a}_3$ complex to oxygen.

Conclusion

Oxygen is the last electron acceptor that accepts electrons from cytochrome $a{a}_3$ complex and consequently forms water molecules.