Ribulose-1,5-bisphosphate (RuBP) is a five-carbon sugar phosphate that plays a crucial role in the process of photosynthesis. It is a key substrate in the Calvin cycle, where it reacts with carbon dioxide to produce glucose and other carbohydrates. RuBP is essential for converting inorganic carbon into organic forms that can be used by plants and other photosynthetic organisms. In the Calvin cycle, RuBP is catalyzed by the enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (often abbreviated as RuBisCO). This reaction is vital for the fixation of carbon dioxide, making RuBP a central component in the global carbon cycle and a fundamental element in sustaining life on Earth.