The study reported in this article investigated the use of metaphors by upper secondary and tertiary students while learning a specific content area in molecular life science, protein function. Terms and expressions in science can be used in such precise and general senses that they are totally dissociated from their metaphoric origins. Beginners in a scientific field, however, lack the experience of using a term of metaphorical origin in its domain-specific precise and general sense, and may therefore be more cognitively affected than the expert by the underlying metaphor. The study shows that beginners in the field of molecular life science use spontaneous metaphors and metaphors used in teaching in a way that demonstrates that they have difficulty using the proper scientific terminology. The results of this study indicate, among other things, that difficulties in science education may, to a large degree, be connected with problems of communicating the generality and precision of scientific terms and metaphors used in science. The article ends with a suggestion as how to enable students to move from general and vague metaphoric uses of scientific terms toward a more general and precise usage. (Contains 7 figures.)