We and many other animals share the same colour of the blood that is red. Anyway there are many other creatures living on earth with different colours of blood. Here we are going to find out what color and why they are coloured so.
Red blood caused by the protein known as haemoglobin. Iron atom in this molecule bind to the oxygen we breathe in order carry it to other parts of the body. The reaction changes haemoglobin's structure so it absorbs and reflects light differently; that's the reason why the oxygenated blood appears red while deoxygenated blood is darker.
While the green blood belong to some marine worms and leeches. They have molecule called chlorocruorin in their blood. The protein have similar structure to haemoglobin, anyway it make their blood green instead of red. There are also animals with blood contains both chlorocruorin and haemoglobin, and it makes their blood color closer to red. So the green blood are not belong to alien out of the space!
There are also creatures with blue blood such octopuses, squid, spiders and some other molluscs. The blue color produced by protein called haemocyanin. Haemocyanin flows freely in the vessels, and contains copper atoms rather than iron. It might appear blue when oxygenated, it is actually colourless when deoxygenated.
When those colours might be in your imagination but not this one, 'purple'. Purple blood colours belong to some species of marine worms and brachiopods. This colour contribute by the protein called haemerythrin. Similar to haemocyanin, haemerythrin is colourless in deoxygenated. While this protein contains iron atoms, compared to haemoglobin it isn't suited to binding with oxygen molecules.
So that's it. There are many other colours of blood that we can include in the next horror movies.
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