Topic overview

Start with the big picture

A useful starting point is redox potential: carriers with more negative E°' tend to donate electrons, while those with more positive E°' tend to accept them. Cells use this progression in pathways such as the mitochondrial electron transport chain, where electron flow is coupled to proton movement, and photosynthetic systems, where light initiates transfer. Different carriers handle electrons in distinct ways: flavoproteins can bridge transfers involving one or two electrons, iron–sulfur proteins and cytochromes commonly carry single electrons, and ubiquinone can shuttle electrons with protons. Transfer depends on molecular distance and protein environment. The broader lesson also considers proton-coupled transfer, reactive oxygen species, alternative electron acceptors, and consequences of disrupted electron transport.