Practical 4: ENZYMES
PRE-LABS
1. What is a catalyst and a catalysis reaction?
Catalyst: Catalysts are substances that increase the reaction rate of a chemical
reaction without being consumed in the process.
Catalysis reaction: Catalysis reaction is a process of increasing the rate of a chemical
reaction by adding catalyst.
2. Compare the basic difference between chemical catalysts and biological catalysts.
Chemical catalysts
Biological catalysts
Substances that increase the rate of a
Biological molecules that increase the rate of
chemical reaction
biochemical reaction
Have low molecular weight
Have high molecular weight
Are less efficient
Are highly efficient
Function at high temperature
Function at a specific temperature. In low
temperature, they are inactive; in high
temperature, theyget denatured.
Are small molecules
Are globular protein
3. What are enzymes? Describe their basic four properties?
Enzymes are proteins that act as biological catalysts by accelerating chemical reactions.
Four basic properties of enzymes:
1.
2.
3.
4.
Catalytic Property
Specificity
Reversibility
Sensitiveness to heat and temperature and pH
4. How many types of enzyme are there? List them and give at least 1 example.
There are 6 types of enzyme: oxidoreductases, transferases, hydrolases , lyases, isomerases
and ligases.
Types
Biochemical Property
Example
Oxidoreductases
These catalyze oxidation and reduction reactions
Dehydrogenase
Transferases
These catalyze transferring of the chemical group from one
Kinase
to another compound.
Hydrolases
They catalyze the hydrolysis of a bond.
Proteases
Lyases
These catalyze the breakage of bonds without catalysis.
Carboxylase
Isomerases
They catalyze the formation of an isomer of a compound.
Isomerase
Ligases
Ligases catalyze the association of two molecules.
Ligase
5. Define the term “optimal temperature” of an enzyme.
The temperature or pH at which a compound shows its maximum activity is called
optimum temperature or optimum pH, respectively.
6. What makes biological catalysts specific? Define the “active site” of the enzyme and the
“substrate”
Biological catalysts, enzymes, are extremely specific that catalyze a single chemical reaction or some
closely associated reactions. An enzyme’s exact structure and its active site decide an enzyme’s
specificity. Substrate molecules attach themselves at the active site of an enzyme.
The enzyme’s active site is a cleft or a pocket within the enzyme where the substrate molecule binds
and undergoes chemical reactions to be converted into the product.
The substrate is a molecule upon which an enzyme act.