Metabolism

Every cell in your body does 5 things:

converts energy
digests nutrients
excretes waste
reproduces
takes in oxygen

Metabolism is made of two distinct processes:

catabolic — breaking compounds down (in order to release energy)
anabolic — building of compounds (which uses energy)

You are not only made up cells, but you only count as ‘living’ for as long as your body effectively mirrors the activities of your cells. In other words, you and your cells need to do exactly the same things, because you are ultimately the cells that compose you.

The Italian doctor Santorio Sanctorius (1561-1636) devised a set of experiments to precisely measure fluctuations in his weight. He would regularly weigh himself before each meal, weigh the food and drink he was about to consume, and then weigh himself again after the meal. Then he would sit on a scale and watch his weight decrease over time. He would also weigh his urine and excrement, and calculated how much more goes into the body than ever seems to come out. He proved, beyond a shadow of a doubt, that most of what we consume just seems to disappear, through some kind of mysterious ‘insensible perspiration.'1

Of course, what we consume does not really disappear: it is metabolized, converted to the animating energy that we describe as ‘life’. Rocks only ‘do’ one thing: they erode. If your heart stopped beating (thus ceasing to circulate oxygen throughout your body) you would erode too. In fact, you’d disintegrate even faster than the rock. But while you are alive, your body valiantly battles erosion. Your body’s first and most important mission is to keep putting itself back together, at a molecular level. You do this by metabolizing enough energy to remain in a more-or-less consistent state of self-repair and regeneration.

Another notable dissimilarity is that the temperature of the rock is always moving towards equilibrium with its environment: put the rock in either a hot or cold place, and it will eventually become exactly the same temperature as the place you leave it. On the other hand, as long as you are alive, your system will do everything possible to keep your core internal body temperature steady, at about thirty-seven degrees celsius. What powers this remarkable thermal regulation? Enter: Sanctorius’ ‘insensible perspiration’.

What is the point of this reflection? If we strip everything else away, perhaps the best way to describe life is that it is a planetary uprising against entropy. Life is a rebellion against the forces of dispersion and fragmentation. Our enemy is decay itself. Like the erosion of the rock, time always moves in the direction of order to disorder. Like the grains of sand on the beach, everything disintegrates and divides, ever smaller, and ever more scattered. Like an office desk or backyard shed, everything moves consistently towards disorganization. But then life shows up. One molecule at a time, life harvests whatever energy it can metabolize and organizes itself into a tiny erosion-battling machine – bacteria, plants, and animals alike. A general characteristic of all life seems to be “entropy reduction.”2

To be alive is to seek order. Literally, it’s in your genes, and it is an operation manifested by the activity every cell in your body.


  1. Eknoyan, Garabed. (1999). Santorio Sanctorius (1561-1636)-founding father of metabolic balance studies. American Journal of Nephrology; Mar/Apr 1999; 19, 2; pp. 226-233 

  2. Lovelock, James. (1979). Gaia: A new look at life on Earth. Oxford University Press. p. 2 


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Shelley, James. (2020). 'Metabolism' (in System Thinker Notebook). Originally published on August 5, 2020. Accessed on September 29, 2020. Licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Permalink: https://jamesshelley.com?p=17035
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