Uma queda por números em biologia

A feeling for the numbers in biology

Rob Phillips a and Ron Milo b,1

- Author Affiliations

aDepartments of Applied Physics and Bioengineering, California Institute of Technology, Pasadena, CA 91125; and

bDepartment of Plant Sciences, Weizmann Institute of Science, Rehovot 76100, Israel

Edited by Ken A. Dill, University of California, San Francisco, CA, and approved October 30, 2009 (received for review July 14, 2009)

Abstract

Although the quantitative description of biological systems has been going on for centuries, recent advances in the measurement of phenomena ranging from metabolism to gene expression to signal transduction have resulted in a new emphasis on biological numeracy. This article describes the confluence of two different approaches to biological numbers. First, an impressive array of quantitative measurements make it possible to develop intuition about biological numbers ranging from how many gigatons of atmospheric carbon are fixed every year in the process of photosynthesis to the number of membrane transporters needed to provide sugars to rapidly dividing Escherichia coli cells. As a result of the vast array of such quantitative data, the BioNumbers web site has recently been developed as a repository for biology by the numbers. Second, a complementary and powerful tradition of numerical estimates familiar from the physical sciences and canonized in the so-called “Fermi problems” calls for efforts to estimate key biological quantities on the basis of a few foundational facts and simple ideas from physics and chemistry. In this article, we describe these two approaches and illustrate their synergism in several particularly appealing case studies. These case studies reveal the impact that an emphasis on numbers can have on important biological questions.

bionumbers order of magnitude physical biology

Footnotes

1To whom correspondence should be addressed. E-mail: ron.milo@weizmann.ac.il

Author contributions: R.P. and R.M. designed research, performed research, analyzed data, and wrote the paper.

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.

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