BioNumbers and the importance of quantification

Have you ever wondered how many ribosomes there are in a cell? Or needed to know what the concentration of malate is inside a cell? Being able to give numerical estimates is really important in the biological sciences, but is something biology undergraduates are often very bad at. I came across the quite excellent BioNumbers website today – the site houses ‘A Database of Useful Biological Numbers’ and as such is a really useful resource to support the development of this skill. Huge numbers of quantitative values are included in the database, which can be either searched or browsed by keyword. For example, entries for DNA include the rate of DNA replication in humans (33 nucleotides/second), the amount of genomic DNA in a diploid cell (~6pg/cell) and the rate of mutation in the mitochondrial genome (~2.7×10-5 substitutions/site/generation).

Given the flood of data emanating from new molecular techniques there is every reason to believe that more and more quantitative hints will be available for ever more sophisticated inferences about the mechanisms of biological action. – Phillips and Milo (2009)

Being able to quantify biological parameters isn’t just something that impresses examiners (although you should be aware that numbers do gain marks in exams, even in essays). Although it often isn’t taught this way in schools, biology is an inherently quantitative discipline – experimental data is rarely expressed in terms of the raw units directly obtained but some form of calculation is usually required. In addition, biology is increasingly using the tools of mathematics, engineering and physics in order to understand complex problems, so being confident with quantitative data is a fundamental skill required by contemporary biologists. Why not start out your appreciation of biological data by having a sense of the approximate sizes, concentrations and rates of common molecules and cell types – if you don’t know how much of something you are expecting how can you check if your calculations are correct?!

For a more detailed discussion of quantitative biology, and some nice case studies, have a read of Phillips and Milo (2009) ‘A feeling for the numbers in biology’ PNAS DOI:10.1073/pnas.0907732106

Reference: Milo et al. Nucl. Acids Res. (2010) 38: D750-D753.


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