TeXes Science Practice Test 2026 - Free Science Exam Practice Questions and Study Guide

Proteins are primarily composed of amino acids, which are organic compounds that serve as the building blocks of proteins. Each protein is made up of one or more polypeptide chains, which are sequences of amino acids linked together by peptide bonds. The specific arrangement of these amino acids determines the structure and function of the protein.

Amino acids contain an amino group, a carboxyl group, and a unique side chain that distinguishes one amino acid from another. There are 20 standard amino acids, and the sequence in which they are arranged and folded results in various protein functionalities, ranging from catalyzing biochemical reactions as enzymes to providing structural support in cells.

The other choices refer to different types of biological molecules: fatty acids are components of lipids, nucleotides are the building blocks of nucleic acids like DNA and RNA, and carbohydrates consist of sugar molecules. While these molecules are vital for various biological functions, they do not form proteins, further emphasizing the importance of amino acids as the primary constituents of proteins.