Before revision: Living cells can sense their environment with high precision. Yet, the resources required for sensing with high precision is an open question. Here we address this question for both equilibrium and non-equilibrium systems. We find that in equilibrium systems the precision of sensing is fundamentally limited by the number of receptors;
After revision: Living cells deploy many resources to sense their environments, including receptors, downstream signaling molecules, time and fuel. However, it is not known which resources fundamentally limit the precision of sensing, like weak links in a chain, and which can compensate each other, leading to trade-offs between them. We show by modeling that in equilibrium systems the precision of sensing is fundamentally limited by the number of receptors;