Wherever water cannot persist, biomolecules cannot function. So liquid water marks the regime we know as hospitable. The chemical bonds between atoms require intimate contact. But out in the darkness of our galaxy, a random hydrogen atom may collide with another only once every few thousand years. If on our planet the evolution of life were paced so slowly, we could not hope for wonders from such lonesome molecules.
Photons transport the energy.
Life makes one further claim on hydrogen that is much less of a commonplace. The linkages that unite molecules are strong and generally created by the transfer or sharing of electrons between bound atoms. But some type of chemical bond gentle enough to permit assembly and disassembly by the atomic environment without disruptive energies is also a necessity for the unceasing transformations of the life stream. That essential bond is provided not by electrons alone but by entire hydrogen atoms. While a hydrogen atom is isolated, the single electron remains spherically distributed around the host proton.