Despite doing well in biology at high school, some students struggle with the same subject at university level. This can have implications for epistemological access--access to knowledge that allows students to remain at university. Therefore, it is important to identify factors that may be causing this problem. We propose that one such factor may be differences in the structure of knowledge between the two levels. Therefore, this paper will assess some of the differences in the structuring of knowledge that exist between a high school and a university biology curriculum. To do this, a section of a high school and a university textbook which cover the same topic will be analysed using one aspect of Legitimation Code Theory called Semantics. Our findings suggest that there is a mismatch between the semantic range students are expected to navigate at university and that demanded by high school biology, and that this may pose a stumbling block to students gaining epistemological access to first-year study at university. If this is indeed the case, then pedagogic interventions which explicitly address this may contribute to improving undergraduate student retention and throughput rates at university.