Agree with the conclusion. But: our blood is red primarily because of the aromatic ring of protoporphyrin IX, the iron ions…

Agree with the conclusion. But: our blood is red primarily because of the aromatic ring of protoporphyrin IX, the iron ions bound to it shift only slightly the visible absorption maximum. Blood would be red even without iron.

— Jan Trnka (@jantrnka78) September 8, 2018

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