The formed element described is usually found with which pair of soluble amino acids?

The formed element described is usually found with which pair of soluble amino acids?

• A. Phenylalanine and tyrosine
• B. Ornithine and arginine
• C. Isoleucine and leucine
• D. Acetoacetic acid and β-hydroxybutyric acid

Answer: (B)

This item tests how amino acids relate to a urine formed element through metabolic pathways, focusing on which amino acids are typically found together when that element is involved in nitrogen disposal. Ornithine and arginine are both soluble amino acids that play direct roles in the urea cycle, the body's main pathway for removing excess nitrogen. Because they’re tied to the same metabolic process and are readily excreted in urine, they’re the pair most characteristically associated with the described formed element. The other options either involve amino acids not as tightly linked to this specific pathway (phenylalanine and tyrosine, isoleucine and leucine) or are not amino acids at all but ketone bodies (acetoacetic acid and β-hydroxybutyric acid), which doesn’t fit the criterion of a pair of soluble amino acids.

This item tests how amino acids relate to a urine formed element through metabolic pathways, focusing on which amino acids are typically found together when that element is involved in nitrogen disposal. Ornithine and arginine are both soluble amino acids that play direct roles in the urea cycle, the body's main pathway for removing excess nitrogen. Because they’re tied to the same metabolic process and are readily excreted in urine, they’re the pair most characteristically associated with the described formed element. The other options either involve amino acids not as tightly linked to this specific pathway (phenylalanine and tyrosine, isoleucine and leucine) or are not amino acids at all but ketone bodies (acetoacetic acid and β-hydroxybutyric acid), which doesn’t fit the criterion of a pair of soluble amino acids.