I must admit that this is not a question that I had been wondering about, mainly because I assumed that the reasons would have been known some time ago, given our current ability to do microanalysis of pretty much anything.
So I was surprised to learn that researchers have only just found the reason, that it is due to a particular microbial enzyme.
The enzyme is called bilirubin reductase, and it’s a result of the degradation of red blood cells. Once they break down, a bright orange pigment called bilirubin is produced. Typically, bilirubin is secreted into the gut where it has to be discharged. It can also be reabsorbed, which in excess can cause jaundice, which is when a person’s skin and eyes become yellow.
“Gut microbes encode the enzyme bilirubin reductase that converts bilirubin into a colorless byproduct called urobilinogen,” lead author Brantley Hall, an assistant professor in the University of Maryland’s Department of Cell Biology and Molecular Genetics, said in a media statement. “Urobilinogen then spontaneously degrades into a molecule called urobilin, which is responsible for the yellow color we are all familiar with.”
Now at any parties social gatherings, whenever the conversation turns to the topic of urine, you can impress your friends this little factoid.
You can read the paper that was published in Nature Microbiology here.
If I leave a comment here, will it be a piss-take?
Urine is yellow so you know which snow to not eat. 😛
Here’s another fun fact about yellow pee: we can light a fire with a match because pee is yellow.
German alchemist Hennig Brand thought he might be able to distill gold out of urine because it is yellow. He collected a prodigious amount of both human and animal urine and distilled the hell out of it. His final product turned out to be not gold, but phosphorus, an unknown element, and an element essential to the manufacture of matches.
Urine also tans leather and makes wool into tweed.
The degradation of red blood cells into bilirubin is also responsible for the color change of bruises from red/blue to brown/yellow. It is also responsible for the brown/yellow color of poop.
If you would like your urine to be impressively and excessively yellow, just take a large dose of B vitamins. Any “B complex” vitamin with several times the RDA should do (you easily can find them with a few thousand percent of the RDA).
I cant quite figure out if the social gatherings you go to are the exciting type or not.
The most prominent side effect of Rifampin is to turn the urine bright orange-ish red. And one needs to take it everyday for 4 months. Ugh!
IIRC, we’ve known for years that urobilin is responsible for the yellow color of urine. The discovery is the microbial enzyme that is part of the haem reduction pathway.
Meh. That’s just deferring the answer; now the question becomes why is urobilin yellow?
Right?
(Also, I’m pretty sure that after a few beers, my piss is rather clear. Not yellow)
99% of organic chemistry is yellow.
#4,
It doesn’t ‘turn wool into tweed’, it used to be used as a fixative for the dye in the manufacture of tweed.
Riveting Mano. Can’t wait for the follow-up, why is shit brown.
@13 f13:
Turns out, according to the paper if you follow through the links to Nature, pretty much exactly the same reason.
Though I’m certain that certain shits in the forested regions in the vicinity of Rome are pure white.
Title of paper: BilR is a gut microbial enzyme that reduces bilirubin to urobilinogen
Title of article: Scientists solve mystery behind why pee is yellow
My god, such a dumb angle.
[related]
Back in the day, urine was a resource. So, job creation occurred.
Not quite as bad as some others, but bad enough.
The Worst Jobs In History: Middle Ages (Medieval Documentary)
@xohjoh2n #14:
/s
Holms @15, maybe that’s why it interested Mano. After all, why the presence of some molecule changes the colour of something is physics, not chemistry.
(Dumb to some, oblique to others)
Well, maybe some chemistry.
https://en.wikipedia.org/wiki/Color_of_chemicals