I picked this molecule for one main reason: I was flipping through a physiology book and read this statistic: your body goes through on the order of one liter of bile per day! Did you have any idea? That is up there on my goofy big numbers in your body list, the champion of which is still this: your body contains a few tens of grams of ATP. The vast majority of your energy is supplied through the agency of this ounce or two of ATP. However, it's recycled thousands of times per day, and you go through the equivalent of a hundred pounds of ATP in one day, just to live!
Back to bile. Life faces a conundrum: oil and water don't mix. In some cases, this is advantageous (it allows detergent molecules to form your cell membranes, for one). In a lot of ways, it's problematic, though, and it's something medicinal chemists have to consider every day. There is a fine line to walk - a lot of drugs need to be greasy, to a degree. However, your body has thoughtfully evolved enzymes to chew lipophilic molecules up, plus there is the problem of actually getting the things to dissolve and behave well in your (mostly aqueous) body.
A more mundane but equally crucial example of the oil-and-water problem in vivo is the digestion of fats. If you take a potato chip (French fry, beignet, rasher of bacon, etc.) and drop it in a bowl of water, you'll see an oil slick develop. You will notice that, if everything is working properly, there are no oil slicks in your urine or stool. Essential to this happy situation are bile salts, one of which is deoxycholic acid:
They are pretty much soaps, helping emulsify what would otherwise be a grease puddle in your bowels, improving the situation for absorption, metabolism, and toilet habits.
You will notice the word and molecule bear a resemblance to cholesterol. On the order of half your cholesterol production goes towards making these babies. They also see some use in biology as very mild detergents. They are also useful for helping isolate certain proteins that are associated with cell membranes.
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Did you get those ATP values from the same book as the bile factoid? If so, do you have the title handy?
No idea to be honest, I was sifting through a pile, and that particular fact's been floating around in my head for awhile. But here, from Voet and Voet's Biochemistry, 3rd Edition: "An average person at rest consumes and regenerates ATP at a rate of ~3 mol (1.5kg) h^-1 and as much as an order of magnitude faster during strenuous activity." (p571) I can't find a reference for body ATP content. Neither Voet and Voet nor my favorite physiology textbook (Guyton and Hall, I'm using 9e) seem to mention it. This would seem to indicate my number for ATP turnover is a bit high, it's more like 100#.
I can't find you a reference for the absolute ATP content of the body, but various websites including wikipedia throw around "50g" and "100 mmol" (essentially the same).
In relation to physiology textbooks, I highly recommend "Medical Physiology", by Walter Boron and Emile Boulpaep.
there are no oil slicks in your urine or stool
unless you consume Olestra. Uncle Al expected to see Proctor & Gamble recoup its $500 million FDA-clearance debacle. Imagine 100% all-natural Enviro-whiner crankcase lube in general and 100% all-natural Enviro-whiner San Francisco lube in particular. Who heeds the algae when it cries?
How chorageous of you to try an alliteration in your title! :) "chol" reminds me of "chyle" and "chyme"... but I suppose those are more archaic words than cholesterol.
I heard a bit from the weekly Seed postcast about vibratory molecules being proposed as a new mechanism of smell. Given your propensity towards smelly chemicals, I was hoping you'd comment with your views on this in a future entry.
I actually can't claim to have written that title, it was Robert Pinsky. In the linked poem, he seems to be referring to ichor by the sense most people know it, as the blood of the gods in Greek mythology.
Ichor is also an archaic term for bile, dating back to the "four humours" of medicine, when (it was suggested) health required a balance of four humours, or fluids: black bile, yellow bile, blood, and phlegm. It is from here that we get the still-used words "sanguine" for a confident person (plenty of blood) and "choleric" or just "spitting bile" for an angry person (a surplus of bile, you see).
I have actually been following Luca Turin for awhile; I have started a post on him a few times but was never happy with what came out. Sometime soon...
Assuming you thought those were my words, sorry for not being more explicit!