Scholarly writing in the experimental biomedical sciences follows the IMRaD (Introduction, Methods, Results, and Discussion) structure. Many Biomedical Natural Language Processing tasks take advantage of this structure. The task of interest in this paper is the identification of semantic roles of procedural verbs as a first step toward identifying rhetorical moves, text segments that are rhetorical and perform specific communicative goals, in the Methods section. Based on a descriptive taxonomy of rhetorical moves structured around IMRaD, the foundational linguistic knowledge needed for a computationally feasible model of the rhetorical moves is described: semantic roles. Using the observation that the structure of scholarly writing in the laboratory-based experimental sciences closely follows the laboratory procedures, we focus on the procedural verbs in the Methods section. Our goal is to provide FrameNet and VerbNet-like information for the specialized domain of biochemistry. This paper presents the semantic roles required to achieve this goal.