The Chemistry of Life

The Periodic Table currently has 118 well defined and well characterised chemical elements, but only six primary elements are used to form a biological entity; every biological entity!
The Chemistry of Life

Can chemistry define a smile?


I will apologise straight away for the number of links on this page, but we have to get through an awful lot of technical information if we are even to begin to describe the chemistry of life and, rather than explain everything in detail, I thought a few dozen links to Wikipedia may be preferable to a long monologue of boring, but necessary information in this news article.


Every biological entity comprises of six primary elements, these six elements:-carbon, hydrogen, nitrogen, oxygen, calcium, and phosphorus-make up almost 99% of the mass of every living cell, From these six elements four main classes of biomolecules are produced, these are; carbohydrates, lipids, proteins, and nucleic acids.


A carbohydrate is a biological molecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water); There are more carbohydrates on Earth than any other known type of biomolecule; they are used to store energy and genetic information, as well as play important roles in cell to cell interactions and communications.


Lipids comprise a group of naturally occurring molecules that include fats, waxes, sterols, etc and can be broadly categorised as  hydrophobic or amphiphilic small molecules. The amphiphilic nature of some lipids allows them to form structures such as vesicles, multilamellar/unilamellar liposomes, or membranes in an aqueous environment. Therefore the main biological functions of lipids include energy storage, signalling, and acting as structural components of cell membranes.


 Proteins are very large molecules – macro-biopolymers – made from monomers called amino acids. There are 20 standard amino acids, each containing a carboxyl group, an amino group, and a side-chain. The side-chain is what makes each amino acid different, and the properties of the side-chains greatly influence the overall three-dimensional conformation of a protein. Amino acids can be joined via a peptide bond. In this dehydration synthesis, a water molecule is removed and the peptide bond connects the nitrogen of one amino acid's amino group to the carbon of the other's carboxylic acid group. There are hundreds of amino acids in a protein molecule.

Some proteins perform largely structural roles, but the most important proteins, are the enzymes. Virtually every reaction in a living cell requires an enzyme to lower the activation energy of the reaction. These molecules recognize specific reactant molecules called substrates; they then catalyze the reaction between them. By lowering the activation energy, the enzyme speeds up that reaction, but the activity of the enzyme can be regulated using various modifiers, enabling control of the biochemistry of the cell as a whole.

Nucleic Acids

Nucleic acids, so called because of its prevalence in cellular nuclei, is the generic name of the family of biopolymers. They are complex, high-molecular-weight biochemical macromolecules that can convey genetic information in all living cells and viruses. The monomers are called nucleotides, and each consists of three components: a nitrogenous heterocyclic base (either a purine or a pyrimidine), a pentose sugar, and a phosphate group. The most common nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). The phosphate group and the sugar of each nucleotide bond with each other to form the backbone of the nucleic acid, while the sequence of nitrogenous bases stores the information.


That was the easy bit, we have just described the chemistry of every dead living thing; six elements and four classes of biomolecules is all it takes to identify every living thing. In the laboratory when we are asked to solve certain types of problems we use simple, but specific, tests to identify/eliminate organic and inorganic matter from our enquiries.

The real question now is:

'How does chemistry explain a simple tender moment, a smile of happiness or the need to feed?'

If we can answer these questions then we have the problems of the world in our hands.

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The Dawn of Life
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