catalysts
- Enzymes are proteins that serve as catalysts. Catalysts speed up or slow down reactions, but remain unchanged
induced-fit model
- a model for enzyme action
The mechanism for enzymatic action helps to explain the characteristics of enzymes:
• Enzymes work better as the temperature increases because molecules move faster. The enzyme quits working if the temperature gets too high because the enzyme denatures, or loses its conformational shape.
• The pH can affect the enzyme by causing the active site of the enzyme to change shape.
• Certain chemicals enhance the action of enzymes. Cofactors are molecules that an enzyme requires to work. Many vitamins are cofactors.
• Some chemicals slow down or inhibit enzymes:
- A competitive inhibitor can compete with the substrate for the active site.
- A noncompetitive inhibitor can bind to a different part of the enzyme permanently and stop enzyme function.
active site
- the place where the substrate (the reactant molecule)
fits
induced-fit hypothesis
- The substrate comes into contact with the active site, and the active site induces a fit around the substrate
catalytic cycle
- the enzyme mechanism. The substrate fits into the active site of the enzyme. The bond is broken, the
products are released, and the enzyme remains intact.
Enzyme specificity appears to be a function of the enzyme’s
- active site
Enzymes bind to particular substrates because
- the shape and charge of the active site is complementary to the substrate
True or false?
The active site is a rigid pocket in the enzyme that is perfectly shaped to match the shape of the substrate molecule.
- false
Non-enzymatic molecules that are close in shape to the enzyme substrate, but are non-reactive, are
- competitive inhibitors
The specificity of the active site of an enzyme is determined by the
- amino acid sequence