Enzymes Flashcards
What are enzymes?
They are tertiary structure proteins that catalyse reactions.
Are enzymes big or small?
They are relatively large molecules but only a small part of the enzyme attach to a substrate to catalyse a reaction (active site).
Describe the structure of the active site?
Specific and unique in shape due to the specific fold and bonding in the tertiary structure of the protein.
What does it mean due to the active site having a specific structure?
Enzymes can only attach to substrates that are complementary in shape.
What are the two models that are used to explain enzymes?
Lock and Key
Induced Fit
How do enzymes catalyse a reaction?
They lower the activation energy needed for the reaction to occur and thus speeds up the reaction.
What is the activation energy?
The minimum energy required for a reaction to occur.
Describe the Lock and Key model.
The enzyme is like a lock. The substrate is like a key that fits into the lock due to them being complementary in shape.
Describe the lock and key model in enzyme terms.
The enzyme active site is a fixed shape and that due to random collisions, the substrate can collide and attach to the enzyme.
What is formed when the substrate attaches to an enzyme?
Enzyme-substrate complex.
What happens when the enzyme-substrate complex is formed?
The substrate will slightly distort in shape and that distortion can lower the activation energy. The products are then released and the enzyme active site is empty and ready to be reused.
Which model is accepted between the induced fit model and the lock and key model?
Induced fit model.
Describe the induced fit model?
The enzyme is like a glove and the substrate is like your hand. The empty glove is not exactly complementary in shape to your hand but when your hand enters it, it enables the glove to mould around your hand to become completely complementary.
How do enzymes act as biological catalysts?
They lower the activation energy to speed up the rate of reaction.
Describe the induced fit model.
Substrate binds to (not completely complementary) active site of enzyme.
This causes the active site to change shape (slightly) so it is complementary to substrate.
So enzyme-substrate complex forms.
This causes bonds in substrate to bend/distort which lowers the activation energy.
