This material helps to connect this new concept with information you already know.

Suppose you are on the banks of a rushing, rapids-filled river and want to go to the other side. If you simply try to walk across, it will take you a lot of time and energy to battle the current, avoid the rocks, and get out on the other side. However, if there were a sturdy bridge across the river, you could walk across quickly and with much less effort. In some sense, an enzyme active site is a bit like the bridge, providing a lower-energy path for the conversion of substrate (you on one side of the river) to product (you on the opposite side of the river). The example would be even more relevant if the bridge only allowed people of a certain size and shape to cross.