The Origin of Life

Step 3: Synthesis of Proteins and Nucleic Acids

Ultimately the goal of molecular synthesis is to form complex molecules such as proteins and nucleic acids.

Proteins

Proteins form long, chain-like molecules called polymers, and are made up from amino acids. As an example the protein insulin is made from 51 amino acids. Proteins are the main structural and functional agents in a cell. An illustration of a complex protein may be viewed by scrolling to the bottom of page http://www.biochem.ucl.ac.uk/bsm/pdbsum/9wga/main.html.

In the game of molecular synthesis, proteins are extremely important because one group of proteins, known as enzymes, are biological catalysts. They have the function of delivering the right chemicals to right place for organic synthesis.

Nucleic Acids

If molecules are to be useful in the 'life-business' they need to be able to copy themselves, for self-replication is one of the essential characteristics of living organisms. Important here are the two nuclei acids DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).

DNA (deoxyribonucleic acid) is a very important biological compound. It occurs in the nuclei of cells and is the principal component of chromosomes. DNA contains, in encrypted form, the instructions for the manufacture of proteins. Encoded within DNA of an organism, is the order in which amino acids should be strung together to form all the necessary proteins. The key to understanding DNA is in its molecular structure. This can be viewed at: http://www.biochem.ucl.ac.uk/bsm/pdbsum/103d/main.html. Click on the images to the top left for an enlargement. The vital feature here is that DNA forms a double helix — you will see that the structure forms two spiral staircase-like structures which are inter-twined. It is this structure which is the key to its ability to replicate. Details of the DNA molecule are described in the text at http://www.sigmaxi.org/amsci/articles/95articles/cdeduve.html.

RNA (ribonucleic acid) is a close relative of DNA. It can both act as a catalyst and can create a copy of itself from raw materials. Details of what RNA is and its structure can be found at http://www.rnabase.org/primer/. Some scientists think that RNA may precede DNA in the evolutionary process and that once the world of molecular biology was dominated by the RNA molecule. Details are given at http://www.panspermia.org/rnaworld.htm.