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Do you know why your blood is red? It’s thanks to the red blood pigment, haemin, which is one of the components of haemoglobin.

And why do I know this? Well, because I’ve been reading up on Hans Fischer, the German biochemist who was born on this day in 1881, and who was awarded the Nobel Prize for Chemistry in 1930, primarily for his work on the structure and synthesis of the blood pigment haemin. In 1929, Fischer succeeded in synthesising haemin, the deep red, oxygen-carrying, non-protein, ferrous component of haemoglobin, that gives blood its red colour.

It’s elementary, my dear Watson – this is definitely not alien blood.
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Oxygen-rich blood (such as arterial blood and capillary blood) is bright red, as the oxygen intensifies the colour in the haemin. When oxygen is extracted from the blood it turns a darker shade of red – this can be seen in the veins, and in the blood collected during blood donation. The colour of blood can also be an indicator for certain medical conditions. Both carbon monoxide poisoning and cyanide poisoning result in bright red blood, as it inhibits the body’s ability to extract and utilise the oxygen in the blood. On the other hand, severe deoxygenation (which can be caused by respiratory diseases, cardiac disorders, hypothermia, drug overdose or exposure to high altitude) results in a condition called cyanosis, where the blood darkens to such an extent that it gets an almost purple-blueish hue, resulting in the skin turning a blue colour.

While the blood of humans and all vertebrates is always a shade of red (containing haemin), it’s interesting to note that it is, in a strange way, surprisingly close to being green! In addition to his work on blood pigmentation, Thomas Fischer also studied the components of the pigments in leaves. He found that, like the haemin in blood, the chlorophyll in leaves is a porphyrin, and that haemin and chlorophyll share a very similar structure, with only subtle differences.

All of this talk of blood, and red and green pigmentation, conjure scenes of science fiction in my mind – if haemin (that makes blood red), is so similar to chlorophyll (that makes leaves green), perhaps the idea of green-blooded aliens is not such a stretch. It makes scientific sense, right?

Anyway, let me rather stop before I get too carried away. Enjoy the day, and keep an eye out for those little green men! 🙂