Wandering Towards a Goal: The Key Role of Biomolecules George F R Ellis University of Cape Town February 17, 2017 Abstract FQXI Essay for Wandering Towards a Goal Essay contest. 1 Physics vs Biology How can a universe that is ruled by natural laws give rise to aims and intentions? The key difference between physics and biology is function or purpose. There is no purpose in the existence of the Moon or an electron or in a collision of two gas particles. By contrast, there is purpose and function in all life [7]: “Although living systems obey the laws of physics and chemistry, the notion of function or purpose differentiates biology from other natural sciences. Or- ganisms exist to reproduce, whereas, outside religious belief, rocks and stars have no purpose. Selection for function has produced the living cell, with a unique set of properties that distinguish it from inanimate systems of interact- ing molecules. Cells exist far from thermal equilibrium by harvesting energy from their environment. They are composed of thousands of different types of molecule. They contain information for their survival and reproduction, in the form of their DNA”. How does purpose or function emerge from physics? At the macro level, in higher animals and human beings, via adaptive neural networks [10] and physiological systems [15]. At the micro level, through epigenetic effects in cell development [5] via gene regulatory net- works [5] and through adaptive effects in signal transduction networks [9] and synapses [10]. And these are all based at the lower levels in specific molecules: proteins [14] and nucleic acids [19]. 1 To be clear and concise, this paper will focus on voltage gated ion channels. I will first look at the difference between the logic of physics and biology, then at the molecules that make this difference possible, and finally at the way such molecules have come into being and allowed physical processes to generate biological activity. I am taking for granted that living systems are open non-equlibrium systems. That alone does not characterise life: famously, even a burning candle satisfies those conditions. Something more is required. 1 As many readers of this essay will be physicists rather than biologists, hyperlinks are included in the text to help clarify biological concepts introduced. 1