A Journey of Oxygen

Updated Jul 6, 2023

Everything was calm. Millions of oxygen molecules happily went about their business in the room. Suddenly a vast change of pressure hit the air, pulling thousands of air particles towards the nose of an oblivious human. The human had no idea of the journey they were about to send the oxygen on around their body just so they could survive. Amongst the masses of inanimate $O_2$ molecules there lay a self-aware intelligent oxygen molecule. It is not known how he came to be but what is known is that his name was Dave; Dave the oxygen molecule.

After what seemed like an eternity, Dave and the many other particles around him reached the entrance to the human. Most were pulled into the nose but Dave felt ambitious. He used his telekinetic powers to push himself towards the human’s mouth because he wanted to be different. It was dark and wet inside. The human’s tongue was blocking the way to the trachea so it was a tight squeeze but Dave made it through anyway. However, what he found next did not best please him. Dave was a rather solitary oxygen molecule and didn’t much like other particles, so when he was greeted by a rushing torrent of air coming from the nose he wasn’t too happy. The rush of air pulled him quickly down into the trachea. After a short moment he could see the windpipe split off into the two main bronchi just ahead. He made a swift movement to the side and flew down into one of the tubes and continued through the network of passages into an alveolus.

As soon as Dave had entered the alveolus he could feel himself being drawn towards the edge of the structure. Without warning Dave diffused through the surface, into the blood stream, bonded with a haemoglobin molecule and was on his way. Every beat of the human’s heart pushed him forward with a tremendous force and soon he had reached the set of capillaries where he would leave the blood and venture ahead by himself. Once again he quickly diffused but this time back out of the blood and into tissue fluid. He diffused to a cell, across its cytoplasm and ended up in the mitochondria.

Dave had no idea. It all happened so quickly. He felt himself being torn apart as his two oxygen atoms split and re-bonded elsewhere. Dave was no longer self-aware. He no longer had special powers. He was no longer an oxygen molecule, but rather part of a $CO_2$ and $H_2O$ molecule. Half of him, the $CO_2$, took the opposite journey that Dave took. It diffused back into the blood, into the lungs and was exhaled. The water could have taken a number of possible journeys. It could have passed through the kidneys to the bladder and then journeyed on to the water treatment infrastructure. It also could have been excreted through the skin as sweat or breathed out as water vapour along with the $CO_2$. But this water molecule travelled to one of the human’s eyes, diffused onto the surface and formed part of a single tear in memory of Dave.

All that was left of Dave now was a lonely $CO_2$ molecule destined to either be used by a plant for photosynthesis or contribute to global warming, and an $H_2O$ molecule whose fate remains unknown.

To be continued?

Written in GCSE biology for Mr Oakley.