College science courses pose complex challenges to students. Textbooks are dense and laden with textbook features that may be confusing to students unfamiliar with science texts. Courses are especially challenging because they presuppose a certain degree of disciplinary literacy, or understanding of the knowledge and practices possessed by those who create that knowledge within a specific discipline. This study explores how students' disciplinary literacy in the sciences is negotiated by students' prior experiences, background knowledge, and science identities. Analyses of interviews from four students enrolled in an introductory chemistry course in an urban community college reveal that neither knowledge nor identity presuppose one another, instead coexisting in the dynamic and complex process of disciplinary literacy development.