Enzymes Flashcards
What is an enzyme?
Tertiary structure proteins that catalyse metabolic reactions.
What is the lock and key theory?
In a successful collision, the substrate fits perfectly into the active site of an enzyme, forming an enzyme-substrate complex. When this reaction occurs, the products are released.
What is the induced fit theory?
The active site and substrate are not fully complementary. The correct substrate forces its way into the active site and both areas slightly change structure.
How do enzymes catalyse reactions?
They lower the activation energy of a reaction but remain unchanged.
How does temperature affect enzymes?
At low temperatures, enzymes have low kinetic energy so there are less successful collisions.
At higher temperatures, kinetic energy increases so there are more collisions and ES complexes formed.
If temperature is too high, vibrations between the molecules can weaken the hydrogen bonds in the tertiary structure of the active site which causes the enzyme to change shape (denature)
How does pH affect enzymes?
Large changes in pH disrupts ionic and hydrogen bonds and can permanently change the shape of the active site, preventing the formation of ES complexes.
How does substrate concentration affect enzymes?
Increasing substrate concentration will increase successful collisions and rate of reaction. At some point, adding more substrates has no effect as all the enzymes have full active sites.
What is a competitive inhibitor?
They are complementary to the shape of the active site. They prevent the formation of ES-complexes by blocking the active site.
What is a non-competitive inhibitor?
Bind to the enzyme away from the enzyme at an allosteric site. This alters the shape of the active site so no ES-complexes can be formed.
