Describe the action of enzymes including how they are denatured, using the lock and key model

 The key is the enzyme and substrate is the lock. Like a key only unlocks one lock, the active site on the enzyme only fits in 1 type of substrate. Extreme temperature or pH (how acidic something is) denatures enzymes which alters the shape of the active site. This means the 'key' that is the active site on the enzyme will not fit into the 'lock' substrate.