How urea is produced and trace the part taken by a molecule of time it in liver to leaves body as urine?

Urea is the main nitrogenous waste product of protein metabolism in humans and other mammals. It is produced in the liver and excreted in the urine.

Production of urea

The production of urea takes place in the liver through a series of reactions known as the urea cycle. The urea cycle involves the following steps:

1. Formation of carbamoyl phosphate: This step involves the reaction of ammonia with bicarbonate to form carbamoyl phosphate.

2. Addition of carbamoyl phosphate to ornithine: Carbamoyl phosphate then reacts with ornithine to form citrulline.

3. Transport of citrulline to the mitochondria: Citrulline is transported from the cytoplasm to the mitochondria.

4. Formation of argininosuccinic acid: In the mitochondria, citrulline reacts with aspartate to form argininosuccinic acid.

5. Cleavage of argininosuccinic acid: Argininosuccinic acid is then cleaved into arginine and fumarate.

6. Formation of urea: Arginine then reacts with water to form urea and ornithine.

Transport of urea to the kidneys

Once urea is produced in the liver, it is transported to the kidneys through the bloodstream. The kidneys filter the urea from the blood and excrete it in the urine.

Time taken for urea to travel from liver to kidneys

The time taken for urea to travel from the liver to the kidneys varies depending on the individual. However, it typically takes around 30 minutes for urea to reach the kidneys.

Excretion of urea in the urine

Once urea reaches the kidneys, it is excreted in the urine. The amount of urea in the urine varies depending on the individual's diet and fluid intake. However, the average person excretes around 25 grams of urea per day.