Summary

Albert Szent-Györgyi’s *Bioenergetics* (1957) argues that life’s fundamental processes are driven by the transfer of energy through electronic excitation and charge separation, not merely by classical chemical reactions. The book synthesizes his Nobel Prize-winning work on vitamin C and cellular respiration to propose that biological energy flows via a “molecular engine” based on the movement of electrons along conjugated molecular chains, particularly in proteins and flavins. Szent-Györgyi emphasizes that living systems exploit quantum mechanical principles, such as electron delocalization and semiconduction, to achieve efficient energy conversion. A reader takes away a unified view of bioenergetics as a physical phenomenon rooted in submolecular electronics, challenging purely biochemical models.

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Key concepts

Electronic excitation — The absorption of energy that raises an electron to a higher orbital, which Szent-Györgyi posits as the primary currency for biological work.
Conjugated double bonds — Alternating single and double bonds in molecules (e.g., in carotenoids or flavins) that allow electron delocalization and energy transfer along chains.
Semiconduction in proteins — The ability of certain protein structures to conduct electrons like semiconductors, enabling charge separation and energy flow without heat loss.
Flavoproteins — Enzymes containing flavin cofactors that Szent-Györgyi highlights as key sites for electron transfer in respiration and photosynthesis.
Charge transfer complexes — Weak associations between electron-donor and electron-acceptor molecules that facilitate reversible energy storage and release in cells.