Which statement best describes the difference between essential and non-essential amino acids?

• A. Essential amino acids cannot be made by the body and must be obtained from the diet; non-essential can be synthesized by the body.
• B. All amino acids must be obtained from the diet.
• C. Essential amino acids can be synthesized by the body; non-essential cannot.
• D. Non-essential amino acids cannot be synthesized.

Answer: (A)

The main idea is that essential amino acids are those the body cannot make in sufficient amounts, so they must come from the diet, while non-essential amino acids can be produced by the body from other compounds. The statement that best describes this is that essential amino acids must be obtained from food, whereas non-essential amino acids can be synthesized by the body. This aligns with how metabolism handles amino acids: some are not produced in adequate quantities and rely on dietary intake, while others can be generated internally through transamination and other pathways. The other ideas—being required to obtain all amino acids from the diet, or that essential amino acids can be synthesized, or that non-essential amino acids cannot be synthesized—misstate how the body handles these nutrients.