The concept of the primordial sandwich was proposed by the

chemist A chemist (from Greek ''chēm(ía)'' alchemy; replacing ''chymist'' from Medieval Latin ''alchemist'') is a scientist trained in the study of chemistry. Chemists study the composition of matter and its properties. Chemists carefully describe th ...

Günter Wächtershäuser Günter Wächtershäuser (born 1938 in Gießen) is a German chemist turned patent lawyer who is widely known for his work on the origin of life, and in particular his ''iron-sulfur world theory'', a theory that life on Earth has hydrothermal origin ...

to describe the possible origins of the first

cell membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment ( ...

s, and, therefore, the first cell. According to the two main models of

abiogenesis In biology, abiogenesis (from a- 'not' + Greek bios 'life' + genesis 'origin') or the origin of life is the natural process by which life has arisen from non-living matter, such as simple organic compounds. The prevailing scientific hypothes ...

RNA world The RNA world is a hypothetical stage in the evolutionary history of life on Earth, in which self-replicating RNA molecules proliferated before the evolution of DNA and proteins. The term also refers to the hypothesis that posits the existence ...

and iron-sulfur world, prebioticFrom the roots pre (meaning before) and biotic (referring to life), the word prebiotic can refer to the time before life appeared on the earth or any other planet with the capacity to harbor it. processes existed ''before'' the development of the cell membrane. The difficulty with this idea, however, is that it is almost impossible to create a complex molecule such as RNA (or even its molecular precursor, pre-RNA) directly from simple organic molecules dissolved in a global ocean (Joyce, 1991), because without some mechanism to concentrate these organic molecules, they would be too dilute to generate the necessary

chemical reaction A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the pos ...

s to transform them from simple organic molecules into genuine prebiotic molecules. To address this problem, Wächtershäuser proposed that concentration might occur by concentration upon ("

adsorption Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the ''adsorbate'' on the surface of the ''adsorbent''. This process differs from absorption, in which a f ...

to") the surfaces of minerals. With the accumulation of enough

amphipathic An amphiphile (from the Greek αμφις amphis, both, and φιλíα philia, love, friendship), or amphipath, is a chemical compound possessing both hydrophilic (''water-loving'', polar) and lipophilic (''fat-loving'') properties. Such a compoun ...

molecules (such as

phospholipid Phospholipids, are a class of lipids whose molecule has a hydrophilic "head" containing a phosphate group and two hydrophobic "tails" derived from fatty acids, joined by an alcohol residue (usually a glycerol molecule). Marine phospholipids typ ...

s), a

bilayer A bilayer is a double layer of closely packed atoms or molecules. The properties of bilayers are often studied in condensed matter physics, particularly in the context of semiconductor devices, where two distinct materials are united to form jun ...

will self-organize, and any molecules caught inside will become the contents of a

liposome A liposome is a small artificial vesicle, spherical in shape, having at least one lipid bilayer. Due to their hydrophobicity and/or hydrophilicity, biocompatibility, particle size and many other properties, liposomes can be used as drug deliver ...

, and would be concentrated enough to allow chemical reactions to transform organic molecules into prebiotic molecules. Although developed for his own iron-sulfur world model, the idea of the ''primordial sandwich'' has also been adopted by some adherents of the

model.

Notes

External links

Minerals and the Origin of LifeAstrobiology, Volume 2, Number 4, "The First Cell Membranes"
{{Origin of life Origin of life

See also

Notes

External links