Students should be able to: Appreciate the Models & Functions of Enzyme Action

Question 1

The lock and key model covered at GCSE was originally thought to be an accurate model of enzyme action
It suggested that

Answer 1

rigid shape of the active site of the enzyme was a precise fit for the specific shape of the substrate

Question 2

New techniques have allowed scientists to discover that proteins are not rigid structures

Answer 2

Experiments showed that multiple regions of an enzyme molecule moved in response to the environment
Many of these movements were minimal but some of them were more significant

The larger movements occurred when the substrate bound to the enzyme

Question 3

These findings led to the now widely accepted induced fit mode which is what .

Answer 3

Prior to binding, the substrate and active site and not completely complementary in shape

When the substrate binds the active site alters shape and moulds around the substrate

Question 4

There is evidence to support the induced fit model

Answer 4

X-ray diffraction techniques allow for 3D pictures of molecules to be formed

This technique was used to produce pictures of the enzyme hexokinase before and after it bound to its substrate glucose

The images confirmed that the active site of the enzyme changed shape after the substrate bound

Question 5

Enzymes have a wide variety of functions within organisms. They catalyse both intracellular and extracellular reactions which determine the structures and functions of not only cells but the whole organism!