If you're using information from a single source more than once in succession (i.e., no other sources referred to in between), you can use a simplified in-text citation.
Cell biology is an area of science that focuses on the structure and function of cells (Smith 15). It revolves around the idea that the cell is a "fundamental unit of life" (17). Many important scientists have contributed to the evolution of cell biology. Mattias Jakob Schleiden and Theodor Schwann, for example, were scientists who formulated cell theory in 1838 (20).
Note: If using this simplified in-text citation creates ambiguity regarding the source being referred to, use the full in-text citation format.