Question 25

Urea is derived from the breakdown of amino acids in the liver.

Urea is primarily produced through the process of breaking down amino acids in the liver, where excess nitrogen is converted into urea for excretion.

A) Removal of bases from nucleic acids in cell cytoplasm

This option is incorrect because the removal of bases from nucleic acids does not directly contribute to the formation of urea. Instead, this process is associated with nucleotide metabolism and not with the urea cycle, which is linked to amino acid degradation.

B) Breakdown of amino acids in the liver

This option is correct as urea is synthesized from the deamination of amino acids in the liver. During this process, the nitrogen from amino acids is converted into urea, which is then excreted by the kidneys, highlighting the liver's crucial role in nitrogen metabolism.

C) Production of ammonia in the heart

This option is incorrect because ammonia production primarily occurs in the liver during amino acid catabolism, not in the heart. While ammonia is a byproduct of nitrogen metabolism, it is converted to urea in the liver, making the heart irrelevant to urea synthesis.

D) Breakdown of carbohydrates in the intestine

This option is incorrect as the breakdown of carbohydrates does not involve the formation of urea. Carbohydrate metabolism primarily produces glucose and other energy sources, rather than the nitrogenous waste products associated with amino acid degradation.

Conclusion

The correct answer is B, as the breakdown of amino acids in the liver is the primary source of urea production. All other options are incorrect because they pertain to processes that do not directly relate to urea synthesis, emphasizing the specific role of the liver in nitrogen metabolism.