That green blooded son of a...

[Atellus]

As McCoy was apt to say.

 

I was watching an episode of Star Trek which featured a Vulcan who bled a lot. This got me thinking about the colour of blood and why it is the colour it is. In particular, I pondered why a Vulcan should have green blood. The official explanation according to Trek Lore appears to be that a Vulcan's blood is copper based, but if that were so, then surely they are not metabolising oxygen as oxygen would not bind to the iron-containing haem group?

 

Apparently there are some species of lizard which have green blood. I have also heard that horseshoe crabs have blue blood which is blue when oxygenated and colourless when deoxygenated.

 

Discounting the copper based theory, what explanations are there for the green appearance of blood and why might this be an advantage in an oxygen environment?

[insane_alien]

iron complexed with the haemoglobin and oxygen is the cause of our red blood.

 

copper could be the cause but i would have thought that would give a blueish blood. its entirely possible that other chemicals in the blood can cause the colouration. i mean why should vulcans have the same biochemistry as us earthlings.

[YT2095]

Spock actualy stated that rather than Iron their blood was Copper based.

 

Copper based blood actualy exists here on earth too, IIRC Squid and some insects have this.

[swansont]

And besides, it's science fiction

[Mokele]

The lizards with green blood have normal blood that's laced with a colored toxin to make them unpalatable to predators. Blue blood (colorless when deoxygenated) is copper-based hemocyanin, used by annelid worms and many arthropods. Green is just hemocyanin combined with assorted other bodily fluids.

 

Mokele

[Atellus]

So the green colouration is not necessarily indicative of the presence of copper?

 

Why is the blue blood colourless when deoxygenated, when the blood of most other species is not?

 

 

 

And besides, it's science [i']fiction[/i]

 

Which is providing the inspiration for a valid and interesting question about the constituents, structure and function of the blood of different species. A function which science fiction has performed for over a century.

[YT2095]

you May find this thread interesting too: http://www.scienceforums.net/forums/showthread.php?t=11765

[Atellus]

Thanks for the link! Answered my questions.