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2 - E. coli as a model system

Published online by Cambridge University Press:  05 October 2014

Kim Sneppen
Affiliation:
Niels Bohr Institutet, Copenhagen
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Summary

DNA, RNA and proteins

The macromolecular building blocks of living cells are DNA, RNA, proteins, polysaccharides and lipids. DNA stores the information needed to make proteins, RNA participates in the assembly of the proteins and the proteins themselves are the final devices that perform the tasks. Lipids form membranes and thereby allow living systems to form separate compartments and cells.

Let us first list the sizes of these building blocks. We do this in units of equivalent information content. DNA is used as the main information storage device. The information resides in sequences of four bases: A,T,C and G. Three subsequent bases form a codon, which codes for one of the 20 amino acids (aa). The genetic code is shown in Table 2.1. The weight of a codon is larger for DNA (because it is double stranded) than for RNA (single stranded), which in turn is heavier than the amino acids it codes for:

DNA: 2000 daltons per codon,

RNA: 1000 daltons per codon,

Proteins: 110 daltons per amino acid.

Here 1 dalton = 1 g mol−1 = 1.7 · 10−27 kg (~ the mass of one hydrogen atom). This hierarchy of masses does not reflect the amount that is present in a cell, because of the amplification in copy number at any step in the conversion of information from DNA to mRNA to proteins.

Type
Chapter
Information
Models of Life
Dynamics and Regulation in Biological Systems
, pp. 17 - 35
Publisher: Cambridge University Press
Print publication year: 2014

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  • E. coli as a model system
  • Kim Sneppen, Niels Bohr Institutet, Copenhagen
  • Book: Models of Life
  • Online publication: 05 October 2014
  • Chapter DOI: https://doi.org/10.1017/CBO9781107449442.003
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  • E. coli as a model system
  • Kim Sneppen, Niels Bohr Institutet, Copenhagen
  • Book: Models of Life
  • Online publication: 05 October 2014
  • Chapter DOI: https://doi.org/10.1017/CBO9781107449442.003
Available formats
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  • E. coli as a model system
  • Kim Sneppen, Niels Bohr Institutet, Copenhagen
  • Book: Models of Life
  • Online publication: 05 October 2014
  • Chapter DOI: https://doi.org/10.1017/CBO9781107449442.003
Available formats
×