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oxygen in respiration

Doing edexcel unit 5 biology. How is oxygen used in aerobic respiration? Is it only used in oxidative phosphorylation to make water at the end of the process?

Reply 1

Rettajean

In aerobic respiration, oxygen serves as a "final electron acceptor". In order to understand what this means, it's helpful to understand all the steps involved in cellular respiration. There are three main phases of cellular respiration:

1. Glycolysis
2. The Kreb's Cycle (sometimes called the Citric Acid Cycle)
3. The Electron Transport Chain

Glycolysis splits up a glucose molecule into two molecules of pyruvic acid (and some ATP). The Kreb's Cycle takes these pyruvic acids and decarboxylizes them, meaning that through a number of steps, it strips away the carbon atoms to make electrons available. The electrons then proceed to the Electron Transport Chain, and it is here that oxygen is crucial to the process.

Oxygen is a highly electronegative atom, which means that these electrons are very attracted to it and will attempt to move towards it. They get passed through a series of proteins, and this process moves hydrogen protons across a membrane inside the mitochondria. These hydrogen protons, being highly concentrated on one side, will try to diffuse to the other side of the membrane, in order to balance out their concentration. The only way they can return to the other side is through another protein, called ATP synthase. ATP synthase uses the movement of these hydrogen protons down their concentration gradient to create ATP.

The short answer is, oxygen is used in aerobic respiration to draw electrons through the electron transport chain.