Which of the following best describes a complementary protein?

• A. A protein that is denatured by heat and loses its biological function.
• B. A protein that is found only in animal sources and contains all non-essential amino acids.
• C. A protein that, when combined with another, provides all essential amino acids in adequate amounts.
• D. A protein that acts as an enzyme to catalyze biochemical reactions.

Answer: (C)

Verified step by step guidance

1. Step 1: Begin by understanding the term 'complementary protein.' Complementary proteins are two or more protein sources that, when combined, provide all the essential amino acids in sufficient quantities. Essential amino acids are those that the body cannot synthesize and must be obtained through diet.
2. Step 2: Analyze the options provided in the question. Option A describes a protein that is denatured by heat, which is unrelated to the concept of complementary proteins. Option B refers to proteins found in animal sources, but complementary proteins are not limited to animal sources. Option D describes proteins acting as enzymes, which is also unrelated to the concept of complementary proteins.
3. Step 3: Focus on Option C, which states that a complementary protein is one that, when combined with another, provides all essential amino acids in adequate amounts. This aligns with the definition of complementary proteins, as combining different protein sources (e.g., grains and legumes) can ensure a complete amino acid profile.
4. Step 4: Consider examples of complementary proteins, such as rice and beans or peanut butter and whole-grain bread. These combinations illustrate how plant-based protein sources can complement each other to provide all essential amino acids.
5. Step 5: Conclude that the correct answer is Option C, as it accurately describes the concept of complementary proteins. This understanding is crucial for designing balanced diets, especially for individuals relying on plant-based protein sources.