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Pre-cell
A pre-cell (or protocell) is a hypothetical lipid-based structure that, under the RNA world hypothesis, could have confined RNA in ancient times. A pre-cell allowed the RNA to remain in close proximity with other RNA molecules, keeping them concentrated and allowing for an increased reaction rate of enzymes. Pre-cells would have had semi-permeable membranes, allowing only certain molecules to pass through. These enclosed structures may have facilitated natural selection in RNA molecules. Structure Pre-cells are thought to have had a membrane composed of mixed-enantiomer lipid molecules. As natural selection proceeded, pre-cells may have developed stereospecific lipid membranes through frequent fission and fusion of racemic In chemistry, a racemic mixture, or racemate (), is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as racemates. ... pre-cells ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protocell
A protocell (or protobiont) is a self-organized, endogenously ordered, spherical collection of lipids proposed as a stepping-stone toward the origin of life. A central question in evolution is how simple protocells first arose and how they could differ in reproductive output, thus enabling the accumulation of novel biological emergences over time, i.e. biological evolution. Although a functional protocell has not yet been achieved in a laboratory setting, the goal to understand the process appears well within reach. Overview Compartmentalization was important in the origins of life. Membranes form enclosed compartments that are separate from the external environment, thus providing the cell with functionally specialized aqueous spaces. As the lipid bilayer of membranes is impermeable to most hydrophilic molecules (dissolved by water), cells have membrane transport-systems that achieve the import of nutritive molecules as well as the export of waste. It is very challenging to cons ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
