Set 3 — Active Site Theory: Lock and Key & Induced Fit

What are the two models of enzyme action?

Lock and key model and induced fit model

What is the lock and key model?

The substrate fits precisely into the complementary active site of an enzyme

What are the three stages of the lock and key model?

Substrate binds to the active site then an enzyme-substrate complex forms then products are released

What is the induced fit model?

The substrate causes the active site to change shape slightly to achieve a better fit

What is the first stage of induced fit?

The specific substrate approaches and enters the active site

What happens to the active site during induced fit?

It changes shape slightly to fit the substrate

What forms when the substrate fits into the active site?

An enzyme-substrate complex

What happens after the enzyme-substrate complex forms?

The reaction occurs and products are formed

What happens to the products after the reaction?

They are released from the active site

What happens to the active site after the products are released?

It returns to its original shape

What is the main difference between lock and key and induced fit?

Lock and key assumes a fixed active site while induced fit involves a shape change

Why can an enzyme act on only particular substrates?

Its active site has a specific complementary shape and chemical properties

Which model explains a change in the shape of the active site?

Induced fit model