Run The Pathways

Respiration and photosynthesis are usually learned stage by stage, hiding how each stage's products feed the next, and how a loaded carrier like NADH must be emptied back to NAD+, or the pathways stall. This game puts you in charge of a cell that must pay its running costs in ATP. After glycolysis and fermentation, an engulfed bacterium becomes the mitochondrion, as the game compresses a long evolutionary history into one event. There the Krebs cycle loads carriers, an electron transport chain passes their electrons to oxygen while pumping H+, and ATP synthase uses that gradient to make ATP. Then a cyanobacterium becomes the chloroplast the same way, until the cell lives on sugar made from light and saves some for the night.