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Abstract:
The surrounding world can be divided into two parts: alive and inanimate. What makes the difference is the subtle reactivity of living systems. The difference is so great that it is reasonable to suppose that what underlies life is a specific physical state, 'the living state'. Living systems are built mainly of nucleic acids and proteins. The former are the guardians of the basic blueprint while the business of life is carried on by proteins. Proteins thus have to share the subtle reactivity of living systems. A closed-shell protein molecule, however, has no electronic mobility, and has but a low chemical reactivity. Its orbitals are occupied by electron pairs which are held firmly. The situation can be changed by taking single electrons out of the system. This unpairs electrons, leaves half-occupied orbitals with positive electron holes, making the molecules into highly reactive paramagnetic free radicals. The reactivity of the system depends on the degree of its electronic desaturation. Electrons can be taken out of protein molecules by 'electron aceptors' in 'cahrge transfer'. When life began, our globe was covered by dense water vapour. There was no light and no free oxygen. Electron acceptors could be made out of trioses by concentrating their carbon atoms as carbonyls at one end of the molecule. The resulting methylglyoxal is a weak acceptor which made a low level of development possible. When light appeared, free oxygen was generated by the energy of photons. Oxygen is a strong electron acceptor. Its appearance opened the way to the present level of development. The transfer of electrons from protein to oxygen is effected by a complex chemical mechanism which involves ascorbic acid.