Friday, April 30, 2021

It Isn't All Dinosaur Pee

Was the water you bathe in and drink once dinosaur urine? It turns out that some of it probably was, but not all of it. 

Dinosaurs, other than the non-avian variety which we still have as birds, were on the Earth for between 165 and 177 million years. They first appeared between 243 and 231 million years ago, during the Mesozoic Era, and for whatever it's worth, the Mesozoic Era is divided by scientists into three periods: the Triassic, Jurassic and Cretaceous. During this very long period of time the land gradually split from one huge continent into smaller ones. Dinosaurs became extinct around 66 million years ago. This means that they were on Earth for far longer than they’ve been extinct.

Now, about the water. There are more than 326 million trillion gallons of water on Earth. Less than three percent of all this water is freshwater and of that amount, more than two-thirds is locked up in ice caps and glaciers. As I mentioned above, not all of the water we have on earth now is the same that existed over 66 million years ago. That's because not all the water that exists today is exactly the same as what existed then. While the amount of water on earth remains more or less the same over time, molecules of water are constantly being formed and broken apart. 

Water molecules are broken up during photosynthesis in plants. The plants take in carbon dioxide (CO2) and water (H2O) from the air and soil. Within the plant cell, the water is oxidized, meaning it loses electrons, while the carbon dioxide is reduced, meaning it gains electrons. This transforms the water into oxygen and the carbon dioxide into glucose. The plant then releases the oxygen (O) back into the air, and stores energy within the glucose molecules. To make it plain, although plants take in CO2 and release 0, it wasn't the carbon dioxide that became oxygen. It's the water that plants take up through their roots that gets split up, with the O atoms escaping out into the atmosphere. 

If that's the case, then shouldn't we be losing water over time? Not really, because cellular respiration in animals, including humans, produces water as a byproduct. Buckle up, because what follows is that process, and it's not as straightforward as what I described for photosynthesis. 

Animal cells take glucose and combine it with oxygen to create four molecules of adenosine triphosphate, commonly referred to as ATP, and six molecules of carbon dioxide during glycolysis. ATP is the molecule that cells need to store and transfer energy. Additionally, two molecules of water are created during this step, but they are a byproduct of the reaction and not used in the next steps of cellular respiration. It is not until later in the process that more ATP and water are created.

The second step of cellular respiration is called the Krebs Cycle, which is also known as the citric acid cycle or the tricarboxylic acid (TCA) cycle. This stage takes place in the matrix of a cell’s mitochondria. During the continuous Krebs Cycle, energy is transferred to two carriers, NADH and FADH2, an enzyme and coenzyme that play major roles in generating energy. Some people that have difficulty producing NADH, such as those with Alzheimer’s, take NADH supplements as a way to boost alertness and concentration.

The electron transport chain is the third and final step of cellular respiration. It is the grand finale in which water is formed, along with the majority of ATP needed to power cellular life. It starts with NADH and FADH2 transporting protons through the cell, creating ATP through a series of reactions.

Toward the end of the electron transport chain, the hydrogen from the coenzymes meets the oxygen that the cell has consumed and reacts with it to form water. In this way, water is created as a byproduct of the metabolism reaction.

Over the course of the past 66 million years quite a bit of photosynthesis and cellular respiration has taken place in the biosphere. Oxygen and hydrogen atoms have been separated, circulated, and joined over and over again trillions of times. Thus, in an 8 ounce glass of water you may drink a few molecules of water that were once dinosaur pee, but the whole glass of water wasn't. This also means that much of the hydrogen and oxygen in the atmosphere right now was once bonded in molecules long, long ago that were in dinosaur urine. 

All this is simply to show that while this world is ancient, change is the greatest constant.