Editor’s Note: Enjoy this previous article by Dr. Jack Brown, who is on vacation this week.

Why? That’s a question I have heard often from my children, students and one that I still ask often. This curiosity about nature is the foundation of science, and it exists in us all.

We begin life as scientists, intensely curious about the world around us. Some of us never grow up. Science continues to progress today, still driven by the same childhood curiosity and guided by the scientific method, which acts as our candle in the darkness.

The answer to why can vary greatly, from simple to complex. As you progress in science, you comprehend that you are really just taking baby steps, answering an increasingly complex version of why with each step until you encounter the unknown.

Why do we breathe? We must do that to live for sure, but if we keep asking why, the story deepens and we inch closer to truth. Each step towards the answer gets a touch more complicated, and in the biological sciences we often end our questioning once we have explained something chemically.

Sheldon Cooper and the physicists of our planet do not stop at chemistry; the subatomic world beckons to them. Their answers often end in an ocean of mathematical equations. For those who ask “Why do I need math?” ironically enough it is to fully explain the why for basically everything.

Why am I sucking in the atmosphere 17,000 to 28,000 times each day? Most of us know we inhale oxygen and we exhale carbon dioxide. Why? The oxygen is used for a variety of things but mainly to drive the production of a molecule called adenosine triphosphate inside the mitochondria of our cells. This ATP can be thought of as the energy molecule for life.

The oxygen we take in binds with a protein, cytochrome c oxidase, setting at the end of a chain of proteins, which are located on the inner membrane of mitochondria.

This chain of proteins is called the electron transport chain, and it only functions if oxygen is present.

Oxygen is really just the final electron acceptor of the ETC, and it gets converted into water. So we breathe in oxygen and turn it into water in order to make ATP so our cells have the energy they need to live.

The exhale part is mostly the fault of the Krebs or Citric Acid Cycle. If you had my majors biology course, a cold shiver may have just ran over your spine. In these reactions, carbon atoms are stripped from various molecules and added to oxygen to produce carbon dioxide. This is a waste product of the cycle. If you leave carbon dioxide inside you, it will react with the water you are made of and turn into a mild acid. This will drop your pH and you will die.

So, if you do not breathe out, your pH drops and you die. If you do not breathe in, you will not make enough ATP to live. The devil is in the details here for sure, but this answers the why with a touch more detail. #Science

Dr. Jack Brown is the Paris Junior College Science Division chairman. His science articles are published every Sunday.

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