Which term matches the definition: Building blocks of protein.

• A. Calories (energy)
• B. Disinfectant
• C. Organic food
• D. Amino acid

Answer: (D)

The concept being tested is that proteins are built from smaller units called amino acids. Proteins aren’t random substances; they’re long chains of amino acids linked together. The specific order and types of amino acids determine how the chain folds into a particular shape, which in turn decides the protein’s function in the body, such as building tissues, enzymes, or signaling molecules. That’s why amino acids fit the definition of “building blocks of protein.”

Calorie terminology describes energy content, not a component of proteins. A disinfectant is a chemical used to kill germs, not a protein component. Organic food refers to farming or labeling standards, again unrelated to the molecular makeup of proteins. If you remember that proteins are made from amino acids that form chains, the correct concept becomes clear. There are essential amino acids we must obtain from our diet and nonessential ones the body can synthesize, reinforcing why amino acids are the correct term here.