Lesson 3: Formation of Urea

Question 1

Formation of
Urea

Answer 1

Although the kidney has other functions it
is usually associated with the extraction of
cellular waste.

The main cellular metabolic wastes are;

Urea

Uric Acid

Creatinine

All these wastes contain nitrogen as a
major component which is why they
are referred to as nitrogenous wastes.

Question 1

Urea Production

Answer 1

Urea is produced in the liver from the breakdown of excess amino acids
that are the building blocks of proteins. This process is called the ornithine
cycle and requires the use of 3 ATP to produce one molecule of urea.

The amine group (NH2) is removed to release the rest of the amino acid
molecule, which can then be converted into carbohydrates or fats.

The amine group can combine with a hydrogen ion to form ammonia
(toxic), the ammonia is transformed in the liver into the less toxic urea
before it is released into the bloodstream. Two molecules of ammonia and
one molecule of carbon dioxide create one molecule of urea.

Question 2

Waste Products

Answer 2

Another waste product is uric acid which is usually produced by the
breakdown of nucleic acids such as DNA and RNA.

Creatinine is a waste product of muscle action.

These waste products are potentially harmful and therefore must be
removed.