lock and key model

• the substrate fits into the enzyme in same way a key fits into a lock
• the enzyme-substrate complex changes shape slightly to complete the fit, which locks the substrate even more tightly into the enzyme - this is the induced fit model
• induced fit model explains why enzymes are so specific and only bond to one particular substrate
• in the induced fit model the substrate has to be the right shape to fit the active site and has to make the active site change shape in the correct way