Non-iron-based blood elements and color

Not sure about real life examples, but the Vulcans in Star Trek supposedly had copper based blood which was green.

I did a quick Google and there was a little discussion of it - a very little - with someone theorizing the blood could be 'clearish' and turn black on exposure to air/atmosphere. If that were the case, the being could have a translucent complexion... wow. I'm way outta my element here.

Silver ain't going to work because Silver Chloride is very insoluble stuff. Think for a moment about how common chloride is as an anion in living systems.

Here's the answer to that question.

http://www.jewellerycatalogue.co.uk/gold/gold_alloys.php

Cobalt is possible.
Manganese (though Mn(IV) oxide is pretty insoluble), vanadium?

A lot of SF speculates about silicon based life forms, though I'm not sure whether that's specifically about blood chemistry.

I think you could justify blue or green for cobalt based blood. Depends on which oxidation state of Cobalt you use. The colour can be highly modified by the ligands that the Cobalt is complexed to anyway. The complexing molecule does not have to be the same porphyrin-based ligand as mammal blood.

Experiments with Cobalt substituting for iron in hemoglobin have been done (technical article), and it looks like the transition is from Co(II) which I believe is blue to oxygenated Co(III) which is pink (but depends on what other elements are present). The Co-substituted hemoglobin has a much lower affinity for oxygen than the iron form.

Vanadium is another possibility.
http://en.wikipedia.org/wiki/Vanabins

Regarding iron as a trace element in other worked metals, it sounds plausible to me if their technology is low. I'm not an expert, but I could see iron not being completely extracted from surrounding ore during whatever smelting process they're using to produce the metal. Also, if they're using iron tools to work or mold the metal, perhaps some trace of iron could work its way into the finished product.

LeeFlower said:

2. Would an obscenely high mountain (as in fantasy!high as opposed to actually plausible!high) have low enough air pressure/oxygen pressure at the top to warrant copper blood?

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Waylander can correctly if I'm remembering this wrong, but the thing to remember is that oxygen-carrying molecules have to do too things: they have to bind oxygen when the local concentration is relatively high (in the lungs) and they have to be able to release oxygen where the concentration is relatively low. In people, there is a small molecule called DPG that binds to hemoglobin. Its effect is that it makes it harder for oxygen to bind, and easier for oxygen to be released. When you go to high altitude, one of the things that happens to help your body adapt is an increase in DPG levels in the bloodstream, which allows more oxygen to be released to the tissues that need it. You might think of the replacement of iron with a lower affinity metal in the same way.

I don't think you can say how low the atmospheric pressure would have to be make copper more optimal than iron, because that would depend on the other components of the oxygen-carrying molecules - so make it however you like! Just remember that there has to be some minimal amount of oxygen to survive - I don't think there are any animals living near the peak of Mt. Everest, for example.

Here's another question to think about - if your aliens have blood adapted to a low oxygen environment, what would happen when they move to "sea level" (or equivalent). Are they as adaptable as humans to different altitudes? or would the extra oxygen be toxic?

LeeFlower said:

1. Do you know what environments cobalt-blood would be better suited to that iron-blood?

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The most likely explanation for having Cobalt-based blood would be the relative abundancy of the two elements in the local environment. Our Earth is Iron-rich; in a Cobalt-rich world one might expect that the biochemical systems would have elolved to use the most abundant elements.

I love this thread This is a topic I've always been fascinated by although I know nothing about it.

Maybe you could also contact an M.D or a biologist who specializes in something related to blood for example. Tell them you're a writer and they might be willing to answer your questions They probably have access to a lot of information not available to people out of the right fields.
Maybe check the library of the closest university?

This thread might give you some ideas, too. It's about blue skin color rather than blue blood, but blood chemistry is also mentioned:

Low Gravity Question
http://absolutewrite.com/forums/showthread.php?t=24783

the red colour of blood comes from the red blood cells - which are only about 45% of blood (the rest is plasma which is colourless).

If you change the colour of the plasma - perhaps make it blue - then you will have purple blood.

So for example your "people" have an extra organ which needs the blue stuff in the blood to make magic work and hence thier blood is purple.

To your average lay person this will probably work - to a biochemist I have no idea!

Also I beleive that the crabs have blue "blood" because they actually don't have blood - they use plasma and/or lymph to move things around. I know that insects don't use blood - I can't remember about crabs.

But I am away form my textbooks right now so my memory could be faulty

RedandGold said:

Also I beleive that the crabs have blue "blood" because they actually don't have blood - they use plasma and/or lymph to move things around. I know that insects don't use blood - I can't remember about crabs.

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I think it depends on how you define "blood". I think the primary distinction is that in our blood the oxygen is carried by hemoglobin (with iron) which is packaged in red blood cells. In crustaceans oxygen is carried by hemocyanin (with copper) which circulates freely.

RedandGold said:

If you change the colour of the plasma - perhaps make it blue - then you will have purple blood.

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Certainly high levels of some nutrients can cause a color change. For example high levels of carotene in the diet (such as if you subsist on carrots) will turn you yellow-orange and ingestion of silver can turn you blue-grey. You could probably think up another dietary component that give you the desired color.