Final answer:
The key to an enzyme's function is its shape, which enables the specific binding and catalysis of reactions. The active site's three-dimensional shape determines the enzyme's specificity and activity.
Step-by-step explanation:
The key to an enzyme's function is its shape. Enzymes are macromolecules, most often proteins, that speed up chemical reactions by lowering activation energy barriers. The active site of an enzyme has a specific shape that allows it to bind with a compatible substrate, forming an enzyme-substrate complex. This specificity of enzyme function is due to the three-dimensional arrangement of amino acids in and around the active site. The shape of the enzyme not only allows it to bind to its specific substrate but also contributes to its catalytic activity through models such as the lock-and-key and induced fit hypotheses. These models explain that the active site of an enzyme is complementary to the shape of its substrate, or it can change shape to accommodate the substrate, enhancing the enzyme's efficiency in catalyzing reactions.