The Molecules of Life

The Dense (or molecular) Gas Clouds

  Although hydrogen is the most common element in space, its atms are relatively few and far between. There is about one atom per cubic centimetre (cm3) in space between the stars, compared with more than 1 x 10^19 atoms per cm3 in the air you are breathing now. With a density of hydrogen atoms as low as this, there is almost no chance that hydrogen atoms will come together to form hydrogen molecules.

  In dense gas clouds or molecular gas clouds, there are some regions between the stars where molecules do form, though they are hardly dense by standards on Earth. The gas clouds are made up of a mixture of atoms and molecules, mainly of hydrogen, together with a dust of slid material from the break up of old stars.

Cold Chemistry and the 'Molecules of Life'

  Humans are made up of molecules and some ions, rather than single atoms. Molecules are formed in the colder parts of the Universe whe individual atoms happen to meet and bond to one another. (Molecules do not exist in stars because the bonds connecting the atoms cannot survive at the high temperatures there). Molecules and fragments of molecules have been detected in dense gas clouds, both by radio and infrared telescopes on Earth and by spectroscopic instruments caaried by rockets.

Where did the Molecules of Life come from?

  Some scientists have suggested that the molecules in the dense gas clouds were the building blocks which reacted together to make the molecules that form the basis of life on Earth. They believe that the enegy needed to make these reactions take place came from ultraviolet radiation, X-rays and cosmic rays, and closer to Earth from lightning flashes.

What are we made of?

Elements in the body are classified as one of three types:

Major constituent elements, which make up 2-60% of all atoms present; these are hydrogen, oxygen, carbon and nitrogen

Trace elements, which make up 0.01%, e.g. calcium and phosphorus

Ultra-trace elements, which…