Chemistry

Evolution

Evolution


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The battle for iron - the first multi-cell

The first living beings evidently formed under Fe (II) excess conditions, because the Fe (II) -Fe (III) redox system prevailed at a certain point in evolution. With the development of photosynthesis there must have been an ecological catastrophe because the oxidizing atmosphere meant that there was no longer enough water-soluble Fe (II) available. Under these conditions only those cells could survive which were able to extract from the poorly soluble iron hydroxide [Fe (OH)3] to gain enough Fe (III) for their growth. Generally one sees this as an example for the beginning of the development of multicellular organisms and justifies this as follows:

According to the law of mass action, a constant proportion is always soluble even of poorly soluble substances. If the soluble fraction is removed from the equilibrium, soluble material is replenished. When there is a lack of iron, cells form so-called siderophores (iron-bearing proteins), which bind to Fe (III) with high affinity and thus remove it from its equilibrium.

It would be unfavorable for a single cell to release an iron-binding protein into the environment, but then not be able to absorb iron with it due to diffusion processes. Only when, for example, a thread-like cell structure is formed, is there a balance between release and uptake in the vicinity of the cells.

It is easy to imagine that this mechanism led almost automatically to the first formation of multicellular organisms. Siderophores themselves have become a popular object of investigation in complex chemistry, as these proteins can bind iron extremely efficiently. The Fe3+-binding FhuA protein E. colie.g. has a binding constant of 1049. The best-known siderophore is lactoferrin, which in milk ensures that the baby receives enough iron.


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Comments:

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  2. Korey

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  3. Vanderbilt

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  4. Akinwole

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