Dry Joining

On the young Earth, amino acids were able to join together to form a much larger structure called a protein. The formal name of this process is dehydration condensation, which means "dry-joining".

This process is fundamental to life. It is the glue by which small molecules are joined together and it is such a simple process that it occurs naturally just by heating molecules.

When molecules are heated, water easily evaporates from them. As we have seen, water consists of three atoms. If two of these atoms come from one molecule and one from a different molecule, then the parts of the two molecules which are left behind will immediately join together. This is the process of dry-joining.

For example, here are two glycine molecules.

Two glycines ready to dry-join together

When the molecules are heated the circled atoms (an oxygen and hydrogen from one molecule, a hydrogen from the other) join together to form a molecule of water. The remainders of the two glycines also join to form a very short protein.

Two glycines join releasing a water molecule

On the young Earth this probably happened when a pool containing amino acids dried under the Sun or on the slopes of a volcano. In life today there is a special process that controls which amino acids are joined together and in what order.