Photosynthesis and cellular respiration are core concepts in high school biology, as they are at the core of all living things. However, perhaps because students can't see them happening, they very often have difficulty understanding them. Further, students often come into biology with a limited understanding of the law of conservation of matter as it relates to chemical reactions. These problems compound to create a great deal of misconceptions about these two important processes. In these lessons, I implemented the use of modeling to overcome these misconceptions and give my students a firm understanding of chemical equations, photosynthesis, and cellular respiration.