Natural Science 2 (NAS 2) Challenge Practice Exam

The function of a protein is determined by its three-dimensional (3D) structure because the specific shape of a protein allows it to interact with other molecules in a precise manner. Proteins are made up of long chains of amino acids, and the sequence of these amino acids dictates how the chain folds into its unique 3D configuration. This structure includes secondary elements like alpha helices and beta sheets, as well as the overall tertiary structure and potential quaternary interactions with other protein molecules.

The 3D structure is crucial because it creates the binding sites and active sites that enable proteins to perform their functions, whether that be acting as enzymes, signaling molecules, structural components, or transport carriers. A change in the structure, even slight, can greatly affect a protein's function, potentially leading to loss of activity or altered interactions with other cellular components.

Other choices like mass, solubility, and color do not inherently determine a protein's function. While mass may have some relevance to properties like transport in biological systems and solubility can affect a protein's interaction with its environment, neither directly implies how a protein will behave functionally. Color of a protein is generally related to specific chromophores within the protein but does not indicate its biological role