Amino acid metabolism mnemonic

Urea cycle intermediates in order

The mnemonic

Ornithine Carbamoyl Citrulline Argininosuccinate Arginine

What each word stands for

  • OrnithineCombines with carbamoyl phosphate (OTC) to form citrulline
  • CitrullineExported from mitochondria; combines with aspartate
  • ArgininosuccinateFormed by argininosuccinate synthetase
  • ArginineFormed by argininosuccinate lyase; arginase releases urea and ornithine

Why it matters clinically

Defects cause hyperammonaemia; OTC deficiency is the only X-linked one, with raised orotic acid.

Where it stops being reliable

It covers the intermediates, not the enzymes' locations (first two steps mitochondrial, rest cytosolic) or the regulator N-acetylglutamate.

Teaching aid, still awaiting independent review. Confirm facts in a standard source.

More mnemonics

Common questions

What is the Amino acid metabolism mnemonic?

Ornithine Carbamoyl Citrulline Argininosuccinate Arginine. It helps you recall: Urea cycle intermediates in order.

What does "Ornithine" stand for?

Combines with carbamoyl phosphate (OTC) to form citrulline

What does "Citrulline" stand for?

Exported from mitochondria; combines with aspartate

What does "Argininosuccinate" stand for?

Formed by argininosuccinate synthetase

What are all the parts of the Ornithine Carbamoyl Citrulline Argininosuccinate Arginine mnemonic?

Ornithine: Combines with carbamoyl phosphate (OTC) to form citrulline; Citrulline: Exported from mitochondria; combines with aspartate; Argininosuccinate: Formed by argininosuccinate synthetase; Arginine: Formed by argininosuccinate lyase; arginase releases urea and ornithine.

Which topic does this mnemonic belong to?

It belongs to Amino acid metabolism in Biochemistry.

Where does this mnemonic stop being reliable?

It covers the intermediates, not the enzymes' locations (first two steps mitochondrial, rest cytosolic) or the regulator N-acetylglutamate.

How is this useful clinically?

Defects cause hyperammonaemia; OTC deficiency is the only X-linked one, with raised orotic acid.

How do I make this mnemonic stick?

Say it aloud, write it from memory tomorrow, then again in a week. Then test yourself on a Biochemistry question about Amino acid metabolism.

Is this a standard mnemonic?

It is a teaching aid written or adapted by our team. Some resemble ones students share informally. Check any fact that matters in a standard source.