Which attribute of enzymes is primarily determined by their tertiary structure?

The primary attribute of enzymes determined by their tertiary structure is the shape of the active site. Enzymes are proteins that catalyze biochemical reactions, and their functionality is heavily reliant on their three-dimensional shape. The tertiary structure refers to the overall folding and spatial arrangement of the protein, which is influenced by interactions between amino acids, including hydrogen bonds, ionic bonds, and hydrophobic interactions.

The active site of an enzyme is specifically shaped to fit the substrate it acts upon. This shape is crucial because it determines how well the substrate can bind to the enzyme. When the substrate fits perfectly into the active site, the enzyme can effectively facilitate the conversion of substrate to product, a concept often described by the "lock and key" or "induced fit" models. If the active site is altered due to changes in the tertiary structure, either through denaturation or mutations, the enzyme may lose its ability to function properly.

The other choices touch upon attributes of enzymes but are not primarily governed by their tertiary structure. For example, size and weight relate more to the number of amino acids in the protein rather than the folding, while electrical charge can be influenced by the amino acid composition and pH but is not solely a function of the tertiary structure.