The First Thermal Map of a Red Blood Cell Surface

Entropy is often associated with disorder and chaos. However, in biology, it is closely related to energy efficiency and metabolism, the set of chemical reactions that sustain life.

Researchers from the universities of Barcelona and Padua, in collaboration with the Complutense, Francisco de Vitoria of Madrid, and Göttingen universities, have developed a revolutionary new methodology for measuring entropy production on length scales a million times smaller than a centimeter. The results of their work were published in the journal Science with the title “Variance sum rule for entropy production.”

Entropy production and heat flow

This production is directly linked to the heat flow across the surface of red blood cells, which dissipates energy into the surrounding fluid. The result obtained is naturally tiny, a million billion times smaller than a calorie per second — a plate of pasta is equivalent to about 250 calories — but it was measured with absolute precision.

Measuring entropy production

To measure entropy production, the researchers used a technique called optical tweezers to manipulate red blood cells and measure the fluctuations in their membrane. These fluctuations are caused by the incessant motion of molecular motors, the molecules that consume…