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Blood Red?
19 September 2012

Blood Red?

Ever wonder why Spock has green blood? Ask an avid Star Trek fan and they will tell you it’s because his Vulcan haemoglobin, the protein in blood cells that carries oxygen, is based on copper. Human haemoglobin (depicted here in a painting by Irving Geis) is however based on iron. Each haemoglobin molecule is constructed of four identical building blocks made of globin protein (purple) and heme (red). It is the heme group that gives our blood its distinctive red colour. Each heme contains an iron atom surrounded by a ring structure called porphyrin. When porphyrin is bound to iron carrying oxygen, it produces a red colour. While evolution paired up porphyrins with iron in humans, the same is not true for all creatures on earth. Molluscs, like Spock, also use copper giving their porphyrins a green hue.

Written by Lux Fatimathas

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BPoD stands for Biomedical Picture of the Day. Managed by the MRC Laboratory of Medical Sciences until Jul 2023, it is now run independently by a dedicated team of scientists and writers. The website aims to engage everyone, young and old, in the wonders of biology, and its influence on medicine. The ever-growing archive of more than 4000 research images documents over a decade of progress. Explore the collection and see what you discover. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.

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