Brooklyn College BIOL 1010 : Lab Notes
Properties of Enzymes
Metabolism is the complex of reactions that occur within the cells of an organism
Enzyme
Definition:
- a protein molecule that acts as a catalyst
- protein name usually ends in the suffix -ase
Structure:
- a three dimensional globular protein
- shape is complementary to a particular substrate (very specific)
- active site - the region of an enzyme that binds to the substrate
- substrate - the substance on which the enzyme reacts
Function:
- acts as a catalyst by lowering the activation energy
catalyst - a compound that increases the rate of speed of a reaction but is itself not changed during the reaction
activation energy - the amount of energy needed to initiate a chemical reaction
Catalysts at Work
Spontaneous reaction(exothermic reaction)
- a reaction that does not require added energy to begin
- opposite is an endothermic reaction
Spontaneous reaction without a catalyst.
Spontaneous reaction with a catalyst.
- (Note the decreased activation energy allowing more product to be produced.)
Factors Affecting Rate of Catalysts
- Substrate concentration
- Temperature
- pH
All enzymes have "optimal ranges" in which they function most effectively.
Here is a graph showing "optimum pH ranges" for the enzymes: arginase, pepsin, and salvilary amylase.
From the graph, we can see pepsin's "optimum pH" is pH=2.
