The aim of this study is to determine the mental models and misconceptions used by biology teacher candidates in conceptualizing catabolism and anabolism concepts. For this purpose, the study has been conducted voluntarily on 59 biology teacher candidates in 2018-2019 academic year spring semester. In the study, two open-ended questions have been addressed to the students about the concepts of catabolism and anabolism, asking them to make explanation by drawing and writing technique. After the application, students' mental models and also misconceptions about the subject have been determined by analyzing students drawings and explanations. According to the results obtained from students' drawings and explanations, it has been determined that biology teacher candidates have imperfect knowledge and misconceptions about catabolism and anabolism and solution offers have been presented.