Research on external representations in biochemistry has uncovered student difficulties in comprehending and interpreting external representations. This project focuses on students' understanding of three external representations of the potassium ion channel protein. This is part I of a two-part study, which focuses on the affordances and limitations of representations of the potassium ion channel according to students across the chemistry and biochemistry curriculum. Analysis showed that if the students do not possess the required prior knowledge then they are stymied in their interpretations of the representations. Students were able to easily interpret the familiar ribbon diagram representation; however, they found the vines and hydrophobic/polar representations to be less informative. Suggestions for instruction are to probe student understanding and to help students activate prior knowledge to build a more connected set of concepts pertaining to protein structure. (Contains 4 tables and 5 figures.)