why is pee yellow?
In: Biology
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For the same reason that poo is brown. Both are composed of old red blood cells.
The red blood cells get old after about 100 to 120 days. They get more stiff, and find it more difficult to squeeze through the capillaries. Then they get recycled in the spleen.
Have you ever wondered just what the spleen does? Well, it does immune system stuff, it stores spare blood for use in an emergency, and it also breaks down red blood cells.
The spleen is an organ on the left side of your tummy, high up and under the ribs. It’s about 11 centimetres long, and weighs between 150 and 200 grams. It ‘catches’ the old and inflexible red blood cells with mechanical filtration, and breaks them down. It takes a lot of energy to make haemoglobin, so your body doesn’t break it all the way down to its individual atoms.
The ‘globin’ part of the haemoglobin molecule is broken down into individual amino acids. They are recycled to make proteins, including haemoglobin. The ‘haem’ part of the haemoglobin is broken down into iron and a chemical called ‘biliverdin’. From here on, the biochemistry gets very complicated, so I’ll ignore the fancy stuff, and cut straight to the summary. Poo is brown and urine is yellow because of a chemical that gets released when red blood cells are broken down; This chemical goes through seven major ‘transformations’ before it ends up as the brown chemical that gives the brown colour to faeces; During the process of being ‘transformed’, it gets shunted all over the body. It travels between the spleen, the bloodstream, the liver, the gall bladder and the duodenum before it finally exits your body into your toilet bowl — giving your faeces that familiar brown colour; During one of the intermediate stages, this chemical is yellow in colour. It ‘escapes’ from the gut into the bloodstream, but is picked up by the kidneys and ends up in your bladder. This time, it leaves your body via your urethra, and again it enters the toilet bowl — giving your urine that familiar yellow colour.
[https://www.abc.net.au/science/articles/2011/08/09/3288245.htm](https://www.abc.net.au/science/articles/2011/08/09/3288245.htm)
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