potassium

[cjameshuff]

So an organism with a lithium fluoride based chemistry rather than sodium chloride would be very reactive, perhaps safer in a cold environment. Whilst your potassium bromide based silicon life form might need a lot of heat to ensure reactions happened.

Lithium and fluorine are highly reactive, but lithium fluoride isn't notably so. It's actually much less soluble in water than sodium chloride, reducing its availability for chemical reactions (and potassium bromide is more soluble). The chemical properties of the two columns don't even vary in the same way. While fluorine is more reactive than chlorine, and chlorine more reactive than bromine, sodium is more reactive than lithium, and potassium more reactive than sodium.

There's no particular chemical meaning to 1:1 pairings of subsequent rows from different columns of the periodic table, especially for substances that are mostly present in the form of dissociated ions. An organism isn't going to use bromine in preference to chlorine just because it evolved to use potassium in place of sodium.

 

[Rincewind]

Thanks again to all concerned.

I'm learning loads and loads from all the excellent material.

A kinda spoiler.

My story is set on Mars - the Mars of Victorian SciFi, so with Mars being a much more earth-like planet.

I noticed that the Earth has about 10 times more potassium than Mars [thank you Wiki!], but, for instance, Mars has 7 times more Magnesium than Earth.

Hence my search for a possible potassium replacement. I do like the idea of Martians being slightly radioactive, though!

 

[Steve001]

Sorry to yuk up an otherwise informative and smart thread. I remember an episode of The X-Files where there was a sillicon based life form (since sillicon is below carbon on the periodic table).

You must be young or missed the original StarTrek episode "Devil in the Dark"

 

[Hellbound]

You must be young or missed the original StarTrek episode "Devil in the Dark"

Or numerous other TV episodes, movies, books, and similar that have played with the idea off and on for at least 20 years

Oh, and computer games (Masters of Orion)

 

[WhatRoughBeast]

Hence my search for a possible potassium replacement. I do like the idea of Martians being slightly radioactive, though!

Oh, that's no biggie. We've all been there, done that, so to speak. From https://en.wikipedia.org/wiki/Isotopes_of_potassium

In healthy animals and people, 40K represents the largest source of radioactivity, greater even than 14C.

 

[WhatRoughBeast]

Is there another element that could perform the same/similar functions as K for a different form of sentient life?

Well, yes and no. If you mean, is there an element which will substitute for potassium in our biology, the answer is a pretty clear no. Potassium deficiency (hypokalemia) is a real condition, and there is no theraputic substitute for potassium in treating it. Not that folks have looked all that hard, since potassium is cheap and readily available. Even more importantly, there is also a condition called hyponatremia (lack of sodium), and either can occur independently of the other. Some plants, such as sugar beets, can utilize rubidium in place of potassium, at least to some degree, but the same is not true in animals.

For what it's worth, Larry Niven's Destiny Road posits a world with no available potassium, and the resulting ecosphere is lethal to humans.

In the longer term, the obvious candidate is sodium, with similar ionic properties. The changes made in biology to accomodate the differences would be multifarious and often subtle, but it seems the best choice. Just don't try too hard to explain them.

 

[Rincewind]

Well, yes and no. If you mean, is there an element which will substitute for potassium in our biology, the answer is a pretty clear no. Potassium deficiency (hypokalemia) is a real condition, and there is no theraputic substitute for potassium in treating it. Not that folks have looked all that hard, since potassium is cheap and readily available. Even more importantly, there is also a condition called hyponatremia (lack of sodium), and either can occur independently of the other. Some plants, such as sugar beets, can utilize rubidium in place of potassium, at least to some degree, but the same is not true in animals.

For what it's worth, Larry Niven's Destiny Road posits a world with no available potassium, and the resulting ecosphere is lethal to humans.

In the longer term, the obvious candidate is sodium, with similar ionic properties. The changes made in biology to accomodate the differences would be multifarious and often subtle, but it seems the best choice. Just don't try too hard to explain them.

thank you - I particularly like the last sentence!

 

[GlennB]

In the longer term, the obvious candidate is sodium, with similar ionic properties. The changes made in biology to accomodate the differences would be multifarious and often subtle, but it seems the best choice. Just don't try too hard to explain them.

The Na/K pump across nerve membranes is fundamental to nerve function, so I don't think substituting Na for the K there is going to work, as you'd then have the Na/Na pump