Which of the following are examples of conditionally indispensable amino acids?

• A. Leucine and Isoleucine
• B. Phenylalanine and Valine
• C. Glutamine and Arginine
• D. Histidine and Tryptophan

Answer: (C)

Conditionally indispensable amino acids are those normally made by the body but that must be supplied by the diet when the body's synthesis can’t meet increased demands, such as during illness, injury, or rapid growth. Glutamine is the classic example: in catabolic states like burns or severe trauma, the need for glutamine rises and endogenous production may not keep up, so dietary glutamine becomes essential to support gut and immune function. Arginine is another one: in healthy adults it’s often nonessential, but during growth or illness its production can fall short of demand, making arginine indispensable in those contexts, especially in children or under physiological stress. The other options consist of amino acids that are normally essential and must be obtained from the diet, not conditionally indispensable. Leucine, isoleucine, phenylalanine, valine, histidine, and tryptophan fit that category, though histidine is particularly essential in infants.