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The cytoplasm is broadly acknowledged to be a polymer gel. Yet, textbook mechanisms build on the presumption that it is an aqueous solution. The concept of a gel-like cytoplasm is replete with power. Partitioning of ions between the inside and outside of the cell is directly explainable from the cytoplasm's gel-like character and the organization of its water molecules; such partitioning requires zero maintenance energy, unlike ion-pumping mechanisms. The cell's electrical potential is also explainable: substantial potentials are measured in gels, as well as in cells stripped of their membrane. Gels also undergo phase-transition - ransformation of protein and water from one physical state to another. In undergoing phase transition, the gels change volume, ion content, solvency, permeability, etc. changes similar to those experienced by organelles within the functioning cell. The polymer-gel phase transition therefore has the potential to be a central paradigm for mediating many aspects of cell function - particularly movement and including muscle contraction. These ideas are explored in depth in a recent book (Pollack, "Cells, Gels and the Engines of Life,", 2001, www.ebnerandsons.com). Movement by phase-transition is in fact the basis of many types of artificial motion. Hence, the broadly taken approach to artificial motion is in many ways similar to the approach taken by nature. These similarities will be discussed in the lecture.
Date of Conference: Dec. 2006