Why climb the mountain…?
“We choose to go to the moon not
because it is easy, but because it is
hard…because that challenge is
one we are worthy to take”
-John F. Kennedy 9/12/61
Why don’t these organisms
bioluminesce naturally?
Bioluminescence & Changes In Potential Energy
• In order for molecules in a
living organism to
bioluminesce, the electrons
must be accelerated to a
higher energy state
• As the electrons “fall back”,
the difference in energy is
given off as light
• Raising molecules to this
state requires more
energy than most
organisms can provide
What are enzymes and how do
they function?
Enzyme Form
• Enzymes are
complex proteins
consisting of
hundreds of amino
acids
• Enzymes have highly
specific 3D structures
held together by a
combination of strong
bonds and weak
intermolecular forces
How does the function of
enzymes dictate their form?
ACTIVATION ENERGY
• All chemical reactions
require ACTIVATION
ENERGY to allow the
reaction to proceed
• Given the symbol EA,
activation energy is
the minimum amount
of energy needed to
make a chemical
reaction start.
Potential Energy Changes In Chemical Reactions
• In a chemical reaction, the amount of potential
energy changes depending upon whether or not
products are being synthesized or broken apart
• In either case, ACTIVATION ENERGY (EA) is
required to make the reaction proceed
Endergonic v. Exergonic Reactions
• In ENDERGONIC reactions the amount of potential
energy in the products is more than in the reactants
• In EXERGONIC reactions, the amount of potential
energy in the products is less than in the reactants
How does the form of enzymes reduce
the activation energy required for
chemical reactions?
Enzyme Specificity
• Every enzyme is
specific to only one
type of molecule or
polymer
• This substance with
which the enzyme “fits”
is called a SUBSTRATE
• Since only one enzyme
can match with one
substrate, this fit is
called the LOCK AND
KEY HYPOTHESIS
ACTIVE SITES
• The substrate can fit
with only one enzyme
due to the specific
protein shapes
present at the
ACTIVE SITE
• If the active site is
changed/altered, in
cannot fit with the
substrate anymore
Competitive Inhibition and Herbicides
• Herbicides function by
binding to the active
sites of plant
enzymes
• By blocking the
enzyme from binding
with their intended
substrates, necessary
chemical reactions
cannot take place
Coenzymes
• Coenzymes are metal
ions that are part of
the active site
• Coenzymes assist
enzymes in that their
charge helps weaken
the strong bonds in
the substrates
• Ex: Niacin, Cobalt,
Selenium, Zinc
Assisting Chemical Reactions Through Fit
• Enzymes hold the substrate in place at the
active site so that other molecules can react
with the substrate
• Less reliant on random collisions
Reducing Activation Energy
• Since the reaction is
less dependent upon
random collisions, the
molecules involved
need not move as fast
• Since molecules need
not move as fast, less
activation energy
needs to be supplied
at the start
At the end of a reaction, because the enzyme has
not been chemically changed, it may be reused for
another reaction at another time
Example: Lactase
Factors Affecting Enzyme Function
• Because the
relationship between
substrate and enzyme
is so specific,
changing the number
of enzymes reacting
with the substrate (or
vice versa) may affect
the rate of reaction
• Ex: Vmax
DENATURATION
• One way that the rate of reaction may be
reduced is by reducing the number of enzyme
molecules that can fit with the substrate through
altering the shape of the enzyme
• Altering the shape of an enzyme in this manner
is called DENATURATION
• Enzymes may be denatured by drastic changes
in heat, pH or exposure to heavy metal ions
Denaturation and Activation Energy
• Enzymes have a range of
tolerance for change but
outside of this range, they
lose their specific 3D
shape
• Since this new shape
means the substrate can
no longer held in place,
more energy is needed to
make the reaction occur
• Loss of enzyme shape
= higher activation
energy