Models for Enzyme Action

Question 1

What is the ‘lock and key’ model?

Answer 1

• globular proteins
• the enzyme has an active site
• the substrate shape fits into the active site like a keyfits into a lock.
• complementary shape on the substrate
• not only do the shapes have to be compatible, the enzyme and the substrate also have to be chemically compatible.

Question 2

What is the ‘Induced Fit’ Model

Answer 2

• The enzyme and its active site (and sometimes the substrate) can change shape slightly as the substrate molecule enters the enzyme - CONFORMATIONAL CHANGES
• The conformational changes ensure an ideal binding arrangement between the enzyme and substrate is achieved.
• This maximises the ability of the enzyme to catalyse the reaction