A Short Course in Comprehensive Thinking – Part 21 – Mitochondria
They are the human body’s energy centers, and they play a central role in health.
In 2010, I began studying early life on Earth, before the Cambrian Explosion. I soon discovered Nick Lane’s work, and have studied it ever since. Lane is not just a popularizer, but he has had a career of researching key aspects of life on Earth. He is a leading advocate of how life began on Earth in volcanic vents on the ocean floor, called white smokers. His latest book is about the chemistry of early life, and particularly the Krebs cycle and its reverse cycle. The Krebs cycle is how life gets its energy, and the reverse Krebs cycle is how key molecules of life are made. Lane also has worked on free radicals and aging. A key event of life on Earth was when complex cells appeared over two billion years ago. A leading hypothesis is that it began when a bacterium came to live inside an archaean, possibly through either predation or parasitism, but those two organisms formed a partnership and that “swallowed” bacterium became the first mitochondrion. There is virtually no doubt among scientists today that mitochondria are descended from bacteria, and maybe one bacterium.
What I found fascinating was how mitochondria made ATP, which is the coin of energy of all life on Earth that we know of. The human body produces its weight in ATP each day. A “turbine” called ADP Synthase turns ADP into ATP, and it is central to complex life in more than one way, which is where it gets really interesting. The process begins when a molecule of food, whether carbohydrate, fat, or protein, enters the mitochondria, and an electron is stripped off. This is how food provides our bodies’ energy. That electron is then sent down what is called an electron transport chain. That chain has several “nodes” that the electron passes through. When it passes through a node, the energy of its passing is used to move a proton across a membrane. I have made schematics of it here. The reason why it passed down the chain is that an oxygen atom sat at the end of the chain. Oxygen is the second most “electron-greedy” of all elements, next to fluorine. That oxygen atom provides the “suction” to draw the electron down that chain.
Those protons on the other side of the membrane “want” to come back across the membrane, to not only equalize the concentration, but more importantly, to equalize the electric charge. The electric potential of those protons is the equivalent of a lightning bolt. There is only one way back across the membrane: through the ATP Synthase “turbine.” That proton flow provides the power to make ATP. Using protons to drive a turbine is also how bacteria move around, and a schematic is here.
This situation is amazingly complex, and I am only hitting the highlights. The earliest bacteria did not have oxygen as the “vacuum” for sucking the electrons down the electron transport chain. Oxygen only became widely available when a bacterium evolved to split water to get its electron for photosynthesis. In that instance, scientists also believe that it only happened one time, and all oxygenic photosynthesizers are descended from that one bacterium. Before oxygen was used as the vacuum, it may have been hydrogen. Having oxygen as the vacuum turbocharged the process of making ATP. Oxygenic respiration produces several times more ATP than any other process, and made multicellular life possible.
Oxygenic photosynthesis saved Earth’s hydrogen from being blasted into space, which would have meant the end of Earth’s ocean and all life on Earth. Our existence is dependent on those events from eons ago.
Several years ago, I finally saw the scientific explanation for why processed food is so deadly. It basically wrecks the ATP production process and causes what is called metabolic disease, which is the root of all degenerative diseases. Part of the process is that electrons no longer easily sail down the electron chain to oxygen, but the chain gets clogged, the electrons leak out and become free radicals, and bond with other molecules instead of the intended oxygen. I have schematics here. One node of the electron transport chain sits on the outer wall of the membrane, and escaped electrons bond with the membrane (“oxidize” it) and wreck it. Eventually that node is severed, which kills the electron transport chain. When that happens enough, the mitochondrion stops working, and when enough mitochondria stop working, the cell dies. This is partly what ages us. When muscle cells and neurons die in that way, they are highly specialized and are slow to reproduce, if at all. As those cells die off, so do our nervous systems and muscles, which can lead to the organism’s death. That is just one dynamic of the degenerative process, but probably the central one. Other cells that easily reproduce can go haywire and begin reproducing with abandon, which is how we get cancer. And Western medicine does not address metabolic disease, but only manages the symptoms, which is largely worthless (but lucrative).
It was quite a journey to study early life and how aerobic respiration evolved, to then see how processed food causes degenerative disease, and see what they had in common. That is an advantage of developing a comprehensive perspective.