GED Science Practice 2026 – The All-in-One Guide to Master Your Exam!

A protein is a complex molecule made up of long chains of amino acids linked together. It is an essential building block for living organisms and has a wide range of functions including forming enzymes, hormones, and antibodies to support DNA and cell metabolism. Options A, B, and D are incorrect as they do not accurately describe the defining characteristics of a protein. While proteins can be involved in cell membrane structure and function, they are not limited to just this role. Additionally, proteins can be either positively or negatively charged, so describing them as stable particles with a positive charge is inaccurate. Lastly, while some hormones are made up of proteins, not all proteins are precursors to hormones, so this definition is too narrow. Overall, option C is the most accurate definition of a protein.