Saturday, April 22, 2006

Biosynthesis Stage of Growth Metabolism.

Biosynthesis of building blocks for polymers - such as amino acids and nucleotides- follows the Fueling reaction stage of microbial growth metabolism.

Biosynthesis differs from the Fueling stage in that nitrogen (as ammonia) and sometimes sulphur are assimilated into the molecules of metabolism. Nitrogen is not found in the fuelling precursor metabolites.

Generally the end products of biosynthesis are more reduced than the precursor metabolites, and this reduction is achieved by use of NADPH to donate hydrogen. Additionally ATP is also used, so that ATP and NADPH provide the driving force for biosynthesis.

Quoting from Schaechter 2006 Chapter 7:

Biosynthesis, then, more than fueling, reflects the essentially close relation of microbes to plants and animals. While the fueling metabolism of microbes expresses the potential for life forms to scavenge for food and thereby recycle organic material, the biosynthetic metabolism of microbes reminds us of what we have lost in evolving into beings higher in the food chain.

Study Question:
Explain in what way the biosynthesis of amino acids and other nitrogen-containing components of human cells depends ultimately on the biochemical activities of Earth's prokaryotes.

Responses in comments please.


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