Recent comments in /f/askscience

Lupicia t1_j9r10gj wrote

Reply to Why is urine yellow? by nateblackmt

Pee isn't (just) from what you drink. There's not a 1-to-1. Eating and drinking goes through digestion. Food and liquids are absorbed in your small intestine, enter your blood stream, and are processed by the liver. Glucose and nutrients are transported to cells by your red blood cells. They also carry oxygen from your lungs.

Waste of various kinds, byproducts of cells using energy, enters your bloodstream and is carried by red blood cells to your lungs (carbon dioxide) for air-soluble waste and kidneys (urea, salts, etc) for water-soluble waste. Kidneys help keep the balance of water and salt just right. Water soluble waste happens to be yellow. It comes from cells metabolism, breathing, bile, excess soluble vitamins and nitrogen wastes (from protein) and it is dissolved in water.

The rest of what you eat and drink is digested, or is indigestible, and leaves as solid waste. Bile and dead red blood cells and fiber and other non-soluble waste becomes poop.

54

berliniam t1_j9qzfm0 wrote

Reply to Why is urine yellow? by nateblackmt

Breakdown of red blood cells results in bilirubin which gets stored in your gallbladder. It then gets excreted into your intestines and converted a couple times to end up in two “exit” forms: stercobilin (which gives your stool it’s brown color) and urobilinogen which ends up in your bladder and peed out. This urobilinogen oxidizes with air once you pee and converts to urobilin which has a yellow color! People with gallbladder biliary blockages or liver disease which prevents the breakdown excretion of bilirubin may actually have near-pigmentless stool (acholic stool)

The other pigments in your food like from a strawberry or steak are more likely to be broken down in your intestines and excreted as poop (which is already pretty brown so color changes are less perceptible) or end up as colorless contributors to your urine. Beets are a strong example of a pigment that some folks can’t breakdown as well so it gets excreted in both stool and urine and giving a pink or red hue.

657

kovadomen t1_j9qyzvq wrote

Reply to comment by Bad_DNA in Why is urine yellow? by nateblackmt

The yellow color of urine is because of urobilin, the end product of bilirubin catabolism. One part of bilirubin is excreted by GI tract, where it gives the brown colour - stereobilin. The other part is excreted by the kidneys and the urogenital system, it gives the yellow colour - urobilin.

36

fastspinecho t1_j9qx65q wrote

Reply to comment by tonyvila in What will be the environmental impact of de-orbiting 42,000 Starlink satellites every five years? (Explanation in post) by OvidPerl

No, the first-generation satellites weigh only 250 kg.

SpaceX eventually plans to put second-generation satellites into orbit, which do weigh ~1200 kg. However, they will need fewer of them, because they are more powerful than the first-generation satellites. They are not currently capable of putting many of these into orbit, and only have permission to launch 7500 of them in the future.

Spacex ultimately plans for the first-generation satellites to constitute 75% of its fleet.

29

Bad_DNA t1_j9qw2tc wrote

Reply to Why is urine yellow? by nateblackmt

Most all of those pigments are either degraded or go out the other chute. Urine is the body's way of managing a variety of salts and soluble byproducts of protein catabolism. Urea in various concentrations is... yellow

5

Robbo_2991 t1_j9qpbe0 wrote

Reply to How can Doctors tell if one of your kidneys isn't working? by FineLetMeSayIt

Here's a new one I found out over the last year. While in the womb, both kidneys can fuse together making a horseshoe kidney. Turns out I've got one. With one tube going to my bladder. It hasn't effected my life so far. But yeah.

But to answer your questions. As others have stated it'll start with blood tests, then if something is found to be abnormal with them it'll progress to an ultrasound then an MRI. That's what happened with me anyway.

7