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	Podcast:		25. Early Earth and Life Processes
	Episode:		Early Cells
	Category:		Science & Medicine
	Duration:		00:01:10
	Publish Date:		2011-07-28 08:52:24
	Description:		Transcript: A major step in the development of life is the transition from free floating organic molecules in water to cells. Biology cannot develop without some form of compartment or membrane to concentrate chemical reactions and protect the entity from the environment. Scientists do not yet know how this transition occurred on the early Earth, but it’s been shown that the heating and cooling of solutions of amino acids can lead to the formation of a cell-like structure called a proteinoid. Proteinoids are not alive, but they can grow by allowing amino acids to pass through the membrane and eventually they will split. They also can store energy, in some cases, by storing a voltage across their surfaces. So proteinoids and other similar entities may have been the precursors to cells. It’s likely that on the early Earth, this transition occurred steadily and slowly. The selective advantage of cells was probably not obvious for awhile, and so there is no particular time when we can say the first cell developed.
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