Non-essential amino acids are those that can be synthesized by the body.

• A. Conditionally essential amino acids
• B. Amino acids that the body cannot synthesize
• C. Amino acids that can be synthesized by the body
• D. The body must obtain all from diet

Answer: (C)

Non-essential amino acids are those the body can synthesize from other molecules, so they don’t have to come from the diet. The body uses metabolic pathways to build these amino acids from intermediates like pyruvate, oxaloacetate, or alpha-ketoglutarate, so they are available even if not eaten. For example, alanine can be made from pyruvate, and glutamate from alpha-ketoglutarate, with others like serine and glycine derived from related intermediates. Because of these internal biosynthetic routes, these amino acids are considered non-essential.

This contrasts with amino acids that the body cannot synthesize in adequate amounts, which must be obtained from food, and with conditional essentials that are only required from the diet under certain circumstances. The option describing amino acids that can be synthesized by the body best fits the concept of non-essential amino acids.