Proteins from plant sources such as grains, nuts, and legumes are classified as:

Correct Answer: A

Rationale: The correct answer is A: 'incomplete.' Proteins from plant sources like grains, nuts, and legumes are considered incomplete because they often lack one or more essential amino acids required by the body. Choice B, 'complete,' is incorrect because complete proteins contain all essential amino acids in adequate amounts. Choice C, 'indispensable,' is incorrect as it refers to essential amino acids rather than the classification of plant proteins. Choice D, 'dispensable,' is also incorrect as it implies that these proteins are not necessary, which is not the case.

Correct Answer: D

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: A

Rationale: The correct answer is the radical group (R-group) because it is the unique side chain that differentiates each amino acid. The amino group (choice B) and carboxyl group (choice C) are functional groups common to all amino acids but do not make them unique. The peptide bond (choice D) is the bond formed between amino acids in a protein chain, not the group that makes each amino acid unique.

Correct Answer: D

Rationale: The correct answer is D, 'limiting.' In the analysis of the amino acid composition of foods, the amino acid that occurs in the smallest amount is referred to as the limiting amino acid. This term is used because when one essential amino acid is deficient, it limits the synthesis of proteins, making it crucial in determining protein quality. Choices A, B, and C are incorrect. 'Indispensable' and 'dispensable' refer to the essentiality of amino acids, and 'complementary' does not describe the concept of the amino acid occurring in the smallest amount.

Correct Answer: B

Rationale: The correct answer is B: Phytochemicals. Phytochemicals in soy foods can mimic estrogen and may have health benefits. Indispensable amino acids are essential amino acids that the body cannot produce on its own. Neurotransmitters are chemical messengers in the nervous system. Metabolic by-products are substances produced during metabolism.