Question

Component of Ornithine cycle are
A. Ornithine, citrulline and arginine
B. Omnithine, citrulline and fumaric acid
C. Amino acids are not used as fumaric acid
D. Ornithine, citrulline and alanine

Answer 1

Hint: The urea cycle helps to convert excess ammonia to urea in the mitochondria of the liver cells. The urea is created, goes to the bloodstream, and is filtered by the kidneys, and is eventually excreted in the urine.

Complete Answer:
The urea cycle or Ornithine cycle is an important metabolic process in humans that removes excess nitrogen from the body. The coordinated role of six enzymes and two mitochondrial transporters catalyse the synthesis of a molecule of ammonia, α-nitrogen of aspartate, and bicarbonate into urea.

- The Ornithine cycle is made up of four reactions. The first reaction occurs in the mitochondrial matrix. Later reactions take place in the cytosol.
- The first reaction is catalysed by ornithine transcarbamoylase which transfers the carbamoyl group from carbamoyl phosphate to ornithine to produce citrulline. In the second reaction, argininosuccinate synthetase acts as the catalyst. This enzyme uses ATP to activate citrulline by producing an intermediate citrullyl-AMP. This intermediate is invaded by an amino group of aspartate residues to produce argininosuccinate.
- The third step is catalysed by argininosuccinate lyase, which transforms argininosuccinate into fumarate and arginine. The last step is catalysed by arginase that cleaves arginine to create urea and ornithine that completes the cycle.

Therefore, the correct answer is option A i.e., Ornithine, citrulline and arginine.

Note: Malfunctioning of the kidneys can result in the accumulation of urea in the blood, and lead to a disorder called uremia, which is particularly dangerous and may lead to renal failure. Typically, patients with uremia have proteins, creatine, and other chemicals in their blood. This contamination can affect any system in the body.