This AP® Biology content explores cellular energetics, energy capture, storage, and use. In this pathway, learners will explore using a leaf disk assay to measure the rate of photosynthesis and a microrespirometer to record the rate of cellular respiration. Through an analysis of energy in living systems, the role of ATP in cellular energetics, the complex photosynthetic processes that allow cells to capture energy from light, factors that impact the rate of photosynthesis, and the intricate processes that allow organisms to use energy stored in macromolecules to power cellular functions; learners will investigate the interconnectedness between photosynthesis and cellular respiration. AP® is a registered trademark of the College Board, which has not reviewed this resource.