Chemical Reactions & Enzymes
BIOLOGY I
Chemical Reactions:
● Change one set of chemicals into another.
● Reactants - go into the reaction (left side)
● Products - elements or compounds produced by
chemical reaction (right side)
Energy in Reactions
● Chemical reactions that release energy often
occur spontaneously.
● Chemical reactions that absorb energy require a
source of energy.
Which reaction
can occur
spontaneously?
Enzymes & Energy
Activation Energy:the
minimum quantity of energy
which the reacting species
must possess in order to
undergo a specified
reaction.
Exergonic Reaction - energy
is released (products have
less chemical energy than
reactants)
Enzymes & Energy
Endergonic Reaction - One in
which energy must be supplied
for the reaction to occur
(products have more chemical
energy than reactants)
Energy is stored.
Enzymes:
•Proteins which cells use to
speed up biological reactions by
lowering activation energy.
Enzymes:
(AKA Biological Catalyst)
Lock & Key Model
•Usually globular in shape.
•Often have surface depressions called active sites which
allow SPECIFIC molecules called substrates bind to them.
•Have molecules that fit into active site where chemical
change occurs
Reaction:
Product:
Reactants:
Induced Fit Model
● Enzymes:
○ are often are flexible.
○ can change shape when an appropriate
molecule binds to an active site -- known
as Induced Fit
Factors Affecting Enzymes:
•Temperature:Enzyme
activity increases as temperature
increases, and in turn increases the rate of the
reaction; activity decreases at colder temperatures. All
enzymes have a range of temperatures when they are
active, but have certain temps they work best. At
higher temperatures, proteins (enzymes) can be denatured
(destroyed or broken down). (Most human enzymes
Effects of pH on Enzymes
operate at 95-104 degrees F).
•pH: Charged areas of an enzyme can be affected by
+
-
added [H , OH ], thus reducing their action in high
or low pH.
•Substrate concentration: As amount of substrate
decreases, the rate of enzyme activity will decrease
also
Background knowledge: the more H+, the more acidic. The more OH-, the more basic. Amylase- an enzyme in
saliva that initiates the breakdown of starch into sugar. Pepsin- enzyme that breaks down proteins into
smaller proteins in your stomach. Arginase- enzyme that converts toxic ammonia into urea in urinary
system.