 The activities and structures of proteins may be examined in vitro , in vivo , and in silico . In vitro studies of purified proteins in controlled environments are useful for learning how a protein carries out its function : for example , enzyme <unk> studies explore the chemical mechanism of an enzyme 's catalytic activity and its relative affinity for various possible substrate molecules . By contrast , in vivo experiments can provide information about the physiological role of a protein in the context of a cell or even a whole organism . In silico studies use computational methods to study proteins . 
