Enzyme action

• Enzymes

  Enzymes are globular proteins which have a tertiary structure and catalyse reactions. Enzymes are large molecules which have an active site where substrate binds to.

  The active site is specific and unique in shape due to the specific folded and bonding in the tertiary structure. Due to specific active site enzymes can only attach to substrates that are complementary in shape.
• Activation energy

  All reactions require a certain amount of energy before they occur which is known as the activation energy. When enzymes attach to the substrate they can lower the activation energy needed for the reaction to occur and speed up the reaction.
• Lock and key model

  Suggests the enzyme is like a lock and that the substrate is like a key that fits into it due to their complementary in shape.

  Suggests that the enzyme active site is a fixed shape and that due to random collisions the substrate can collide and attach to the enzyme which forms an enzyme-substrate complex

  Once the enzyme substrate complex has formed the charged groups within the active site are there to lower the activation energy and the products are released and the enzyme active site is empty and ready to be reused.
• induced fit model

  Suggests that enzyme is like a glove and the substrate is like a hand, the empty glove is not exactly complementary in shape to your hand but when your hand enters it enables the glove to mould around your hand to become completely complementary.
• induced fit

  Induced fit is when the enzyme active site is induced or slightly changes shape to mould around the substrate (known as conformational changes). when enzymes substrate occurs due to enzyme moulding around the substrate it puts strains on the bonds and lower the activation energy. the products are then removed and the enzyme active site is returned to its original shape. this is now the accepted model for how enzymes function