Inertia of Chemotactic Motion as an Emergent Property in a Model of an Eukaryotic Cell

Chemotaxis is widely seen in many biological systems. Among them amoebic cells from unicellular slime molds to immune cells are believed to directly sense chemical gradients. Here, we construct a model of amoebic cell by taking account of the chemical kinetics as well as a cellular body. The model is composed of discrete grids and a set of rules which define chemical and motional events on each grid. The model can explain the observed features of the cellular locomotion. We find that the simulated cell tends to keep the direction of motion, which reminds us of “inertia” of motion in Newtonian dynamics. The averaged motion of amoebic cells approximately obeys an “underdamped” equation of motion for a short time scale. “Inertia” of chemotactic motion is an emergent property of the system where motion and the signal processing are strongly coupled to each other.