What Does the Color of Blood Have in Common With Vitamin B12?
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Hemoglobin in red blood cells has 4 heme molecules, each comprising a large ring structure called a porphyrin, at the center of which is iron (Fe) that binds oxygen. B12 also has a porphyrin structure that contains cobalt (Co) at the center. Both heme and B12 absorb blue and green light and reflects red light, giving them their bright red color.
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