Yay! It’s time for basic cellular chemistry in my biology class! Last time around the block, about 5 years ago, I had a more in-depth class, but it went over the same stuff. Yeah yeah, great great. Anyway, upon discussion I remembered something that previous teacher had told the class, and something my mom had read about semi-recently (two separate things). Googling hasn’t helped me; I can’t think of anything extra-particular to help me go from a few thousand hits all of the same basic lecture to a few dozen from which I could cull a nice article and show it to the professor.
Basically, my mom read that recently some sulfur-based (ie. not carbon-based) primitive life had been found near some oceanic vent. The only actual discussion to finding said creatures, instead of hypotheticals, is on message boards. Not what I want. Anybody know a good source on this? Mom and I both want a little more information, as her article, long since thrown away, was Reader’s Digest-esque. Horrid, and makes me wonder about the honesty of the article.
Re: the teacher, she had briefly mentioned near the end of class that yeah, most or all of life on the planet uses left-handed amino acids, but not too long ago (at the time) some new right-handed amino acids were found being used by, most likely to my memory, primitive, probably new oceanic vent lifeforms. Was the teacher correct, or accidentally misled, or have I dreamed up some complete balderdash out of her saying something different?
From my understanding, the bacteria around ocean vents use hydrogen sulfide as an energy source, and the bacteria are used by other, more complex, organisms as an energy source, but none are actually ‘based’ on hydrogen sulfide.
Or that’s what The Discovery Channel told me, on a rare occasion when they weren’t redecorating a house or building a Harley.
The vent creatures in question use sulfur, instead of oxygen, as the final electron acceptor (ie oxidizing agent) in their metabolism. They are not sulfur based life forms, they merely “breath” sulfur. some links.
D-amino acids do show up occasionally in biological peptides, most notably in antibiotics such as gramicidin and actinomycin. However, there are no codons for d-amino acids. The biosynthesis of these peptides does not take place on ribosomes.
Glad to hear about the sulfur critters, it’s what side I took on our little bet. Mwahaha. That quarter is mine. Seems like whatever lowbrow publication said it was sulfur-based just phrased things rather poorly.
As for the last paragraph though, I’ll have to pretend to deeply understand what you say (I’m not a molecular anything, I prefer the more dog-sized world :p), since I’m not sure what all that means. Basically the…whatever makes it can’t use it for their own structure or lower activation energy levels with or anything? That’s more what I was wondering about, the creation and usage, not as a byproduct or something, which as far as I know (not very far), no lifeform on Earth can do such, although we can make them in laboratories. And if the creature (?) that makes those d-amino acids doesn’t have the codons for them, and doesn’t make them on the ribosomes, how is it making them? (I admit, we’re not up to this point yet and I remember almost nothing from my previous class.) They may have been what the teacher was talking about, and I presumed they were made on purpose by the cell for use of the cell.
Upon reflection while trying to understand the links in the link you gave to the amino acids, I don’t see how A) repeated abiogenesis would occur again and survive long enough to maybe make a small colony without being immediately out-competed by older life, and B) have researchers manage to find it and decide it uses a few d-amino acids and creates them itself. I’m now suspecting I dreamed this all up years ago, or it was some sort of thought experiment by my teacher.
IANAMB, and I don’t know how the amino acids themselves are made. But the codons (short sequences of DNA or RNA) are (ordinarily) what specifies which amino acids get put together in what order to make a protein. If you’ve got proteins containing nonstandard amino acids, then first you’ve got to make the nonstandard amino acids (presumably using a similar method to how you make the standard ones), and then you’ve got to figure out how to get those aminos into a protein, without using the standard instruction book.