BioNumber of the month 

Cell biology is constantly being enriched by an influx of quantitative data on a host of critical quantities. In these vignettes that also serve as the basis for a book on “Cell Biology by the Numbers” written by Ron Milo and Rob Phillips we explore how a knowledge of key numbers that characterize the behavior of cells can be used to make useful inferences in molecular cell biology. One of the ways we try to make sense of these numbers is by making back of the envelope calculations (so called Fermi problems) in biology. These estimates aim to connect the complexity of many problems in biology and the kinds of clear-cut deductions often used potently in the physical sciences.

Jan 2013 - How quickly do different cells in the body replace themselves?

Dec 2012 - What is the thermal energy scale and how is it relevant to biology?

Nov 2012 - How fast do cells move?

Oct 2012 - How does temperature affect rates and affinities?

Sep 2012 - How many reactions do enzymes carry out each second?

Aug 2012 - What is the water content and component density in cells?

Jul 2012 - How big are nuclei?

Jun 2012 - What is the energetic transfer potential of a phosphate group?

May 2012 - What is larger, mRNA or the protein it codes for?

Apr 2012 - How fast do RNAs and proteins degrade?

Mar 2012 - How many photons does it take to make a cyanobacterium?

Feb 2012 - How large are chloroplasts?

Jan 2012 - What are the concentrations of different ions in cells?

Dec 2011 - What is the pH of a cell?

Nov 2011 - What is the average oligomerization state of a protein in the cell?

Oct 2011 - How big is the “average” protein?

Sep 2011 - What are the most abundant proteins in a cell?

Aug 2011 - How big is a human cell?

Jul 2011 - What is the redox potential of a cell?

Jun 2011 - What are the concentrations of free metabolites in cells?

May 2011 - How big are viruses?

Apr 2011 - How much energy is carried by the photons used in photosynthesis?

Mar 2011 - What is the permeability of the cell membrane?

Feb 2011 - How big are genomes?

Jan 2011 - How big are the molecular machines of the central dogma?

Dec 2010 - What is the thickness of the cell membrane?

Nov 2010 - How many genes are in a genome?

Aug 2010 - What is the concentration of bacterial cells in a saturated culture?

Mar 2010 - What are the time scales for diffusion in cells?

Feb 2010 - How big is a yeast cell?

Jan 2010 - What is faster, transcription or translation?

Dec 2009 - What is the elemental composition of a cell?

Nov 2009 - ATP requirement for the creation of an E. coli cell


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