What are considered the building blocks of proteins?

Amino acids are the fundamental building blocks of proteins. This is because proteins are made up of long chains of amino acids that are linked together by peptide bonds. The sequence and arrangement of these amino acids determine the structure and function of the protein. There are 20 different amino acids that can combine in various ways to form a vast array of proteins, each with unique properties and roles in biological processes, such as catalyzing reactions, providing structure, and regulating metabolism.

The other options do not serve as building blocks for proteins. Fatty acids are the components of lipids, which serve various functions such as energy storage and cell membrane structure. Monosaccharides are the simplest forms of carbohydrates and are the building blocks of more complex sugars like disaccharides and polysaccharides. Vitamins are organic compounds that are essential for various biochemical functions but do not compose proteins. Therefore, amino acids are specifically recognized as the correct answer regarding the construction of proteins.