This blog has been created partly as a companion to Chemistry for the Biosciences, the textbook that I co-author with Tony Bradshaw, and to act as an archive of posts I write for other sites (particularly the OUPblog). Like the book itself, it explores how life on the scale of atoms and molecules has an impact on biology - at the scale of cells, tissues, and organisms - and seeks to demystify a range of biological and chemical concepts.

The blog's name takes as its inspiration the cover of the first edition of Chemistry for the Biosciences, which depicts a gecko seemingly clinging to its surface. To find out what links geckos to chemistry, read this.



Sunday, 9 January 2011

How geckos defy gravity


The background to this blog shows a Day gecko (Phelsuma sp.). As the image suggests, geckos have the amazing ability to defy gravity and walk up walls (and along ceilings).

How do they do this? The answer lies in the anatomy of their toes. Gecko toe pads comprise rows of thousands of tiny hairs called setae (singular: seta). The gecko’s gravity-defying antics are made possible by forces of attraction, which exist between the surface the gecko is climbing on and the setae on the surface of the gecko’s toes. The forces of attraction are what we call dispersion forces.

Dispersion forces are relatively weak. However, while the dispersion force operating between a singe seta and the surface of the wall (or ceiling) is tiny, there are so many setae on the surface of each toe pad that the overall force of attraction (adding up the contributions from thousands of setae) is very strong indeed – strong enough to hold the gecko firmly in place, against the forces of gravity.
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