So – why do we need oxygen?  And where does it come from?

Oxygen on Earth formed through photosynthesis. Ancient microorganisms called cyanobacteria began releasing oxygen by using sunlight to process carbon dioxide and water, to make glucose and oxygen. They split H2O into hydrogen and oxygen, and then combine carbon, hydrogen and oxygen, to make glucose C6H12O6 , a carbohydrate. Excess oxygen is released as a result.

This oxygen is why we humans – and most other living things —  are able to live on earth. This accumulation of oxygen started during the Great Oxidation Event approximately 2.4 to 2.5 billion years ago.

This alone is amazing. But — drilling down, why do living things need oxygen? The answer is: The tiny energy machines inside living cells, mitochondria, need it, to generate the energy the body’s cells need to go and grow.

OK – how do they do this?  If you’re still with me — Mitochondria create energy, specifically ATP (adenosine triphosphate), through a process called aerobic respiration or oxidative phosphorylation. They act as the “powerhouse” of the cell by converting nutrients (pyruvate from glucose) and oxygen into ATP.

Here is a brief breakdown of the process:

Step one: Fuel Preparation —  Pyruvate from broken-down food enters the mitochondrial matrix, where it is converted into Acetyl-CoA and processed. This creates high-energy electrons.

Step Two: The Electron Transport Chain (ETC): These high-energy electrons are transferred to a series of protein complexes in the inner membrane. As the electrons move down this chain, they release energy.

Step Three: Proton Pumping —  The energy released from the electrons is used to pump protons  across the inner membrane from the matrix to the intermembrane space, creating an electrochemical gradient.

Step Four: ATP Synthesis —  The protons flow back into the matrix through a special protein machine called ATP synthase. The flow of protons drives this “turbine,” converting ADP into ATP, which is then released into the cell for energy.

Step Five: Water Production — At the very end of the chain, the “spent” electrons are accepted by oxygen, which combines with protons to form water H2O.

In short:  Mitochondria use oxygen to burn fuel and create a proton gradient that drives ATP synthase to produce the cell’s energy.

And, a last word – all this is a result of biological evolution.

Could the same process emerge on other planets? Or will its own version of evolution produce something wholly different?

© The Times of Israel (Blogs)