This dissertation studies upper primary school students' meaning-making of nutrient uptake. The papers in the dissertation are based on two sets of collected data. In the first, written answers to a national test in biology are studied. In the other, classroom teaching is studied in two schools with an animation about nutrient uptake as a context. In one of the schools is a teacher review held in connection with the animation. The overall analytical method is content analysis, more specifically organizational levels and systemic functional grammar (SFG) is used. In this thesis, the results are discussed from three perspectives. First, it is shown that scientifically correct answers and the connection between the digestive and circulatory system are associated with the number of connections between organizational levels and the presence of the meso level in the descriptions. Nutrient uptake is often described in terms of relocation (in a logistics system), with explicit and / or implicit actors where the process is often expressed metaphorically. Second, the results provide an insight into the reach of the metaphors (affordances and limitations) for students meaning-making of nutrient uptake by tracing where the metaphors come from. The animation uses metaphorical expressions to explain specific functions. The students used several metaphors, some were also taken up and used by their teachers. Third, the results of the dissertation show that students in both schools combine scientific terms with everyday expressions. The students who had a teacher review use more everyday expressions than those who have not. Furthermore, students show signs of scientific meaning-making at the meso level by using everyday expressions about the function of membrane proteins in terms of molecules that go through channels and have their own entrance into the blood.