Enzymes Flashcards
What is an enzyme?
An enzyme is a globular protein which catalyses the rate of a reaction, with a specific tertiary structure
What is an enzyme substrate complex?
Enzymes have an active site with a specific tertiary structure that becomes complementary to specific substrates
Describe how the induced fit model works [5 steps]
- Enzymes have an active site with a specific tertiary structure
- Before the reaction, the active site isn’t complementary to the substrate
- Due to induced fit, as the substrate approaches, the active site changes shape and becomes complementary
- An enzyme-substrate complex forms
- This stresses the bonds in the substrate (lowering the activation energy) and leads to a reaction
What is the lock and key model?
The shape of the active site does not change when the substrate binds to it
What is activation energy?
The minimum amount of energy needed for a reaction to occur
How do enzymes lower activation energy in anabolic reactions?
Since substrates need to be joined together, the repulsion would be reduced to force them to bond together
How do enzymes lower activation energy in catabolic reactions?
Since the substrate needs to have its bonds broken, the active site strains the bonds between the molecule to break them
What is the link between concentration and rate of reaction?
The higher the substrate concentration, the faster the reaction. More substrate means more reactions. If the enzyme is the limiting factor, it’s because the enzymes would have been saturated
How does temperature increase rate?
Enzyme and substrate both have more kinetic energy –> move faster –> more successful collisions –> more ES complexes –> faster rate
How do extremely high temperatures denature enzymes?
Enzymes vibrate so much that H-H bonds break –> changes enzyme’s tertiary structure –> shape denatures as it’s no longer complementary
How do competitive inhibitors work?
Similar tertiary structure as substrates, they compete with them to bind to the active site. More inhibitors decreases the probability at which substrates can bind to the active site
How do non- competitive inhibitors work?
They bind to another part of the enzyme, affecting the rate. This affects the shape of the active site making it no longer complementary
2 ways incorrect pH could denature enzymes
- the H2 ions could bond to the amino acids on the active site and change its charge
- they could disrupt the H2 and ionic bonds, affecting the tertiary structure