1. Urea and Uric Acid Excretion, Urine Composition by: Rachel Kim

2. Urea Excretion Urea: an organic chemical compound found in wastes (product of amino acid catabolism) Its plasma concentration determines the amount of protein in one’s diet First ammonia is converted to urea as it’s going through the uric cycle Then the urea enters the renal tubule through filtration and is then excreted through urine (50% of it’s reabsorbed)

3. Uric Acid Excretion Uric acid (urate): product of the metabolism of certain organic bases in nucleic acids It’s excreted in small amounts in urine because most of its reabsorbed by active transport that’s present in glomerular filtrate But unlike the urea, uric acid is not synthesized from ammonia but is from adenine and guanine from nucleotides

4. Urine Composition For average adults, there’s about 1-2 liters/ 24 hours of urine produced About 95% of urine is water The other 5% remaining is composed of solutes (chemicals that dissolve in water) Main ions found in urine include: Sodium, Potassium, Chlorine, Magnesium, and Calcium Main organic molecules in urine include: Urea, Creatinine, Uric Acids, Ammonium, Sulphate, and Phosphate

6. Review Questions Q: What happens to most of the urea and uric acid before they’re excreted? A: Most of them get reabsorbed Q: What’s the urea? A: Product of amino acid catabolism Q: What’s the uric acid? A: The product of the metabolism of certain organic bases in nucleic acids Q: What is the urine composed of? A: 95% water 5% solutes Q: What 2 groups do the 5% of solutes break down into? A: Ions and Organic molecules