Origin of life

Abiogenesis (Brit.: /ˌeɪˌbaɪoʊˈdʒɛnᵻsᵻs, -ˌbaɪə-, -ˌbiːoʊ-, -ˌbiːə-/), biopoiesis, or informally, the origin of life, is the natural process by which life arises from non-living matter, such as simple organic compounds. It is thought to have occurred on Earth between 3.8 and 4.1 billion years ago. Abiogenesis is studied through a combination of laboratory experiments and extrapolation from the characteristics of modern organisms, and aims to determine how pre-life chemical reactions gave rise to life on Earth.

The study of abiogenesis can be geophysical, chemical, or biological, with more recent approaches attempting a synthesis of all three. Life itself is dependent upon the specialized chemistry of carbon and water and is largely based upon five different families of chemicals. Lipids are fatty molecules comprising large chemical chains of hydrocarbons and play an important role in the structure of living cell membranes, actively and passively determining the transport of other molecules into and out of cells. Carbohydrates are sugars, and as monomer units can be assembled into polymers called polysaccharides, like for example Cellulose the rigid chemical of most plant cell walls. Nitrogenous bases are organic molecules in which the amine group of nitrogen combined with two hydrogen atoms, play an important part. Chlorophyll is based upon a porphyrin ring derived from amine monomer units, and is important in the capture of the energy needed for life. Nucleic acid monomers are made from a carbohydrate monosaccharide a nitrogenous base and one or more high energy phosphate groups. When joined together they form either the unit of inheritance, the gene, made from DNA or RNA, which translates the genetic information into protein structures. The monomer unit of a protein is always one of 20 amino acids, comprising an amine group, a hydrocarbon and a carboxylic acid. Through dehydrogenation, the removal of a water molecule linking the amine to the acid, a polypeptide protein group is formed which has many catalytic metabolic functions for living processes. Any successful theory of abiogenesis must explain the origins and interactions of these five classes of molecules.

...
Wikipedia