What is formed when a substrate fits into an enzyme's active site?

When a substrate fits into an enzyme's active site, it forms an enzyme-substrate complex. This complex is a crucial step in enzymatic reactions, as it brings the substrate into close proximity to the enzyme’s active site, allowing for the chemical reactions to proceed more efficiently.

The active site of an enzyme is specifically shaped to hold the specific substrate precisely, which facilitates the formation of bonds or the breaking of bonds needed to convert the substrate into products. This interaction often involves weak bonds such as hydrogen bonds and van der Waals forces that stabilize the enzyme-substrate complex prior to the transformation into products.

The process is vital because it highlights how enzymes lower the activation energy of reactions, making it easier for substrates to be converted into products.