This protocol simulation allows us to address fundamental questions about photosynthesis and cellular respiration. It makes use of a colorimetric pH indicator to assess levels of photosynthesis and cellular respiration to gather qualitative data. A spectrophotometer then enables the user to quantify the data. For a shorter simulation that focuses only on the qualitative analysis, visit Photosynthesis and Cellular Respiration: A Qualitative Analysis. Related material: What Is pH Again? How Can We Measure pH? What Effect Does Carbon Dioxide Have On the pH Indicator BTB? Photosynthesis and pH How Does the Distance From the Light Source Affect the Rate of Photosynthesis? How Does Light Intensity Affect Photosynthesis? How Does Temperature Affect the Rate of Photosynthesis? How Do Carbon Dioxide Levels Affect Photosynthesis? Color and Spectrum of the pH Indicator BTB Equilibrium and Le Châtelier's Principle How Can We Measure pH? How To Observe Photosynthesis and Respiration Using a pH Indicator