Nursing Acceleration Challenge Exam (NACE) PN-RN Practice Test

An incomplete protein is characterized by a lack of one or more essential amino acids that the body cannot synthesize on its own. In this context, legumes fit the definition of an incomplete protein because they typically do not provide all nine essential amino acids in sufficient quantities. For example, while legumes are rich in some amino acids, they are often low in methionine, one of the essential amino acids.

In contrast, eggs, milk and milk products, and seafood are examples of complete proteins, as they contain adequate amounts of all essential amino acids necessary for human health. Eggs are particularly well-known for their high-quality protein, providing all the necessary amino acids in the right proportions. Meanwhile, animal-based products like milk and seafood also offer a complete amino acid profile, making them valuable sources of protein in the diet.

Thus, while legumes contribute beneficial protein to a diet, they are categorized as incomplete proteins due to their amino acid profile, making them the correct choice for this question.