Question

The induced fit model says enzyme active site can be molded, so why then enzyme are specific for shape of substrate?

Answer 1

Enzymes are proteins, and proteins are basically a large chain of amino acids (polymer). So imagine when the chain is clumped into a 3D thing (see picture), it is slightly elastic (since there are spaces) and can have a bit of movement for the substrate to fit in. However, the shape is specific as it will return back to its original position once the substrate has left. Just imagine a silicone cup, when you stretch it a bit to fit a slightly larger ball in, it expands a little. When u remove the ball, it returns to its original shape. Similarly, the enzyme active site will return to its original shape but can be slightly molded for a short while, and that is what the sentence meant. It’s quite hard to explain without an actual model/ video, so if you don’t understand you can comment below!