Clock Blockers

It is said that, before World War 2, the best scientists were required to speak German because so many scientific discoveries were made in Germany and the papers published with significant scientific breakthroughs were first published in German. The movie Oppenheimer, about the development of the atomic bomb, highlights this situation, as does any history of NASA. The bombs and the space program were led or primarily aided by scientists born and trained in pre-war Germany. That the Nazis drove out so many talented scientist and artists would be added to the list of pointless, horrible crimes against the Germans themselves. The remnant Germany of today is bereft of the downstream talents and families that would have stayed in Germany and benefited the Germans had they not been killed or driven out.

We may add Hans Adolf Krebs to this list of talented young people driven out of their home country thanks to Nazi policies. Krebs was another German Jew, like Albert Einstein, that saw the handwriting on the wall and decamped to Britain where he contributed to our understanding of human metabolism and cellular respiration. Understanding these functions is key to understanding many other things about the human body, including diet and aging. His research on the inner workings of the cell advanced human understanding of ourselves.

Here, we shall look at the basic functions of the human cell with an aim to understand how it converts our inputs into energy, and we’ll consider if the process of cellular respiration reveals physical processes that are common in other domains, and perhaps are universal rules across the universe. I point out that last part, about processes being universal rules, because biology is chemistry and chemistry doesn’t vary in any world humans have looked at, from the deep sea to other planets. Biology may work the same way, and therefore, to understand a biology like cellular respiration is to grasp how life might well work across the universe, or Universe, if you please.

First, a few definitions are in order.

Eukaryotes – an organism consisting of a cell or cells in which the genetic material is DNA in the form of chromosomes contained within a distinct nucleus. Eukaryotes include all living organisms other than eubacteria and archaebacteria.

Catabolism – the breakdown of complex molecules in living organisms to form simpler ones, together with the release of energy, destructive metabolism.

Anabolism – the synthesis of complex molecules in living organisms from simpler ones together with the storage of energy; constructive metabolism.

Aerobic – relating to, involving, or requiring free oxygen.

Anerobic – relating to, involving, or requiring an absence of free oxygen.

Oxidation – a process in which an electron is removed from a molecule during a chemical reaction.

Reduction – the gain of electrons

Redox Cycle – Oxidation and reduction (Redox) reactions represent the transfer of electrons from an electron donor (reducing agent) to an electron acceptor (oxidizing agent).

Glycolysis – the breakdown of glucose by enzymes, releasing energy and pyruvic acid.

Glucose – a simple sugar which is an important energy source in living organisms and is a component of many carbohydrates.

Krebs Cycle – the sequence of reactions by which most living cells generate energy during the process of aerobic respiration. It takes place in the mitochondria, consuming oxygen, producing carbon dioxide and water as waste products, and converting ADP to energy-rich ATP. By the way, I wonder if this was renamed after WW2 because of two other men named Hans Krebs, both of who were high ranking Nazis. Again, the Nazis ruined German science.)

Oxidative phosphorylation – a cellular process where the reduction of oxygen generates high-energy phosphate bonds in the form of adenosine triphosphate (ATP)

Cellular Respiration – a series of chemical reactions that break down glucose to produce ATP, which may be used as energy to power many reactions throughout the body. There are three main steps of cellular respiration: glycolysis, the citric acid cycle, and oxidative phosphorylation.

Just by reading these definitions, the basic cellular processes, and the broader biological processes behind them should be clear. As noted, many of these concepts are applicable across the earthly domain, and therefore, most likely available across the universe.

First it must be understood that humans are eukaryotes, which means we are made up of cells with a nucleus. All animals, plants and fungi are eukaryotes, but there are living organisms, called prokaryotes, that don’t have an inner nucleus. Human eukaryotes are made up of trillions of cells that have a similar manner of working, and so how these cells generate the energy to live is critical to understanding the workings of the entire organism.

The energy ‘currency’ of the eukaryote cell is adenosine triphosphate, also called ATP. This compound is found in virtually every living thing on earth. How ATP manages cellular energy is a miracle all by itself, and worth studying.

To create this ATP, a cell must engage in what is known as catabolism, which is the process of breaking larger molecules of nutrients into smaller molecules which can be oxidized. Catabolism is breaking down, while anabolism is building up. Steroids that build up muscles are known as anabolic steroids for this very reason.

When larger molecules enter a cell, they are catabolized to create energy. This process is known as oxidation. Oxidation is the loss of electrons in a substance, while reduction the gain of electrons. I know, it seems backwards. The important part to know is that it is the movement of electrons that creates energy, which is captured as ATP.

Pause for a moment to consider that it is the gain, loss or change of atomic particles that breaks the chemicals bonds of elements and compounds, which release energy, both in the human cell and in an atomic bomb! Turns out Krebs, Einstein, and Oppenheimer were working on the same process. Nuclear fission and cellular oxidation have a lot in common!

By the way, when you burn wood in a campfire, the wood is being oxidized in a similar manner and it leaves behind a residue due to ‘oxidative stress.’ You can clean up a campfire and start over. Remind me again why we can’t ever solve aging? I think we can.

It is important to note here that the redox cycle can occur both in the presence of oxygen, or not. The Krebs Cycle, also called the Citric Acid Cycle, was a neat summary of the chain of reactions in the human body that allow for food and oxygen to be turned into energy. Krebs identified the steps in aerobic cellular respiration which means it is the process that combines oxygen and glucose from carbohydrates to produce energy. Because the cycle needs oxygen, it is aerobic respiration. Cells can produce energy without oxygen, but this is called anaerobic respiration. The sharper reader may notice that this corresponds neatly with what is called ‘aerobic exercise,’ like running, that requires a huge input of oxygen over the longer term, and ‘anaerobic exercise,’ like lifting weights, that requires energy in the muscles, but doesn’t use immediate oxygen to work. Aerobic cellular reparation as described in the Krebs Cycle, makes water and CO2 as an output, while anerobic respiration produces lactic acid. Again, this is related to what we call have experienced; when you run hard, you breathe hard as your body demands more oxygen and releases more CO2. When your muscles are working hard, they burn or otherwise hurt, and this is because of the build up of lactic acid. Both are part of cellular respiration which has, as its essential component, the Krebs Cycle.

Aerobic reactions and anaerobic reactions are a universal phenomenon, and therefore, subject to all the laws of the larger universe. There is every reason to believe that cellular respiration is a series of universal chemical reactions that catabolize glucose to produce ATP, which is used as energy to fuel the functions throughout the body.

By the way, one other interesting detail: there are organisms that can respire without oxygen if sulfur is present. These sulfur reducing microbes ‘breathe’ sulfur in the way our cells ‘breathe’ oxygen. They produce, as a byproduct, H2S gas, which is foul smelling and toxic in high volumes. Some of the bacteria in the human mouth can digest organic compounds this way but they are the cause of bad breath. The sulfur cycle, like the oxygen cycle, is part of how chemistry defines life in the universal domain.

Further details and a more detailed explanation of the Krebs cycle and cellular metabolism can be found here: