Tuesday, 15 October 2013

Building a Human

Every single cell in your body is made up of four main types of chemical compound: protein, carbohydrate, lipids/fats and nucleic acids. You are made of molecules, precisely defined and complex molecules, but still just molecules.

The difference in scale between a person and a molecule is enormous. A person is around one to two metres tall. A typical chemical bond is around one to two ångstroms. One ångstrom is tiny; one ten-billionth of a meter. If you took the entire population of the Earth, scaled each person to the size of a typical atomic bond and then stacked everyone head to toe, then the stack would be about your height. This means that, while you are made of molecules, it takes a lot of them to make a person!

The most common type of complex biological molecule in your body are proteins. These are the molecular machines that run your cells. Proteins are made up of chains of different combinations of 21 different amino acids. The amino acids themselves are quite simple molecules; typically made up of 5-10 carbon atoms, a couple of nitrogen and oxygen atoms and a sprinkling of hydrogen. We now know enough about protein amino acid sequences, the structure of cells and the structure of proteins that we could make a pretty good effort of making a scale model of a person, or at least the proteins that make them up.


This picture is a plastic scale model of 100 amino acids, representative of all the amino acids in your body, at about the ratio the different types are used to make up the proteins in your cells. They are ready to clip together to make a scale model of proteins, at a scale of about one centimetre for a bond (100 million times larger than the molecules they represent). Using enough copies of this (and lots of plastic models of water molecules) you could make an accurate scale model of 75% of your body. You would need a lot though; 1,000,000,000,000,000,000,000,000 copies of this set of 100 amino acids. The scale model of your body would also stand around 100,000 kilometres tall (1/3 of the way to the moon), and would weigh much more than the entire Earth.

Your body is an incredible molecular machine, made up of a near-unimaginable mixture of complex biological molecules, all running at a molecular scale. Next time you see someone talking about nanotechnology stop and think for a second. You are nanotechnology; a self-organising, self-repairing, reproducing, thinking piece of nanotech.

Software used:
Blender: 3D design of the plastic scale model.

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