Which term matches the definition: The basic units that combine to form proteins.

• A. Fortified foods
• B. Organic food
• C. Botulism
• D. Amino acid

Answer: (D)

Amino acids are the basic building blocks of proteins. Proteins are made when amino acids link together in chains via peptide bonds, forming polypeptides that then fold into three-dimensional shapes required for their specific functions. There are about twenty standard amino acids, and the order in which they are arranged—the sequence determined by the genetic code—dictates the protein’s structure and activity. Some amino acids must come from the diet (essential), while others can be produced by the body (nonessential). The other items describe types of foods or a disease, not the fundamental units that join to form proteins.