What is an enzyme?
Protein; Biological catalyst--increases
the rate of chemical reaction without changing the nature of the reaction
or being altered by the reaction
a. There are about 4000 different enzymes in a typical cell.
b. Generally named by adding the suffix -ase to the name of wither the substrate or the type of reaction catalyzed
for example:
Lactose to lactase
Characteristics of enzymes:
1. Undergo no change
2. Increase the rate of the reaction but do not start it
3. Lowers the activation energy (amount of energy required to start a reaction), but does not alter the net amount of energy added or released
What is a substrate?
Reactants
Active site: The region of the enzyme to which the substrate binds.
Enzymes are relatively specific as to the substrates they can interact
with and reactions they can
catalyze.
Why? The protein chain of each enzyme bends
and folds in a unique way to produce a
characteristic 3D structure (click here
to see 3D structure).
Temp and pH:
Enzymatic activity diminishes
when pH or temp varies from optimum
Cofactor: Chemical component
used by enzyme as tools to aid catalysis (e.g. metal ions)
Many enzymes are inactive in the absence of other
substances known as cofactors. The
enzymes are inactive because of their conformation (shape) and being
unable to interact with a given substrate.
Cofactors are substances that bind to an enzyme and alter the enzyme's conformation so that it can interact with a substrate.
Coenzyme: Class of cofactor,
Organic molecules that directly participate as
one of the substrates, they are altered but are reverted back by a 2nd
enzyme and reused (e.g. vitamins)
