This course aims to show students how the physical principles of conservation, symmetry and locality influence the dynamics of living organisms at the molecular and cellular level. We start with simple equations that embody a physical principle and compare them with experiments on cells or model systems. The importance of the local environment on dynamics at the molecular scale is introduced, and its influence on typical molecular-scale motions explored, including particle diffusion, the forces between particles in various media, and self-assembly of molecules into larger aggregates. Symmetric and asymmetric random processes are explored in 1, 2 and 3 dimensions, and the combined effects of symmetry, in the sense of invariance under an operation, and mass conservation, or the re-use of a limited amount of matter, are shown to constrain how molecular aggregates assemble, stabilise or disassemble. Computer simulations of simple model systems are used as examples for exploration in problems and a semester project. The primary goal of the course is to show students how nature takes advantage of symmetry and conservation, or selectively breaks them, to achieve specific cellular goals, and to understand how computer simulations can be used to study these processes.