Transcript Energy Enzymes

The Hindenberg
The Crash
• The famous Germanbuilt Hindenburg had a
length of 245 m (804 ft)
and a gas capacity of
190,000,000 liters
(6,710,000 cu ft). After
making ten transatlantic
crossings in regular
commercial service in
1936, it was destroyed
by fire in 1937 when it
was landing at
Lakehurst, New Jersey,
with 97 passengers and
crew; 35 people on board
and 1 ground crew
member were killed.
• Hydrogen gas, because it
Hydrogen
is lighter than air, floats
upward in the
atmosphere. People once
used it to lift zeppelins
and other airships into
the sky, allowing transAtlantic voyages by air.
However, because the gas
is so flammable, it
contributed to many
explosive accidents,
including the Hindenberg
explosion in 1937.
Airships now use helium
gas because it is
nonflammable and
therefore a safer lifting
gas.
2H2 + O2 → 2H2O + energy
Enzymes & Energy
• In biological systems,
the are 3 general
energy paths a reaction
can take.
•
• 1.
Exergonic Reaction
- One in which energy is
released (Products have
less chemical energy
than reactants). This
often, however requires
Activation energy to
initiate a reaction.
Endergonic Reaction
Endergonic
Reaction - One in
which energy
must be supplied
for the reaction
to occur
(products have
more chemical
energy than
reactants)
• Catalyzed
Reaction. -
Usually an
exergonic
reaction Which in the
presence of a
catalyst, is
speeded up
because the
action of the
catalyst reduces
the amount of
activation
needed for the
reaction to
occur.
Catalyzed
Reaction
Enzymes
• Enzymes are proteins which cells use to
speed up biological reactions.
• They are usually Globular in shape.
• Often have surface depressions called
active sites which allow
• SPECIFIC molecules to bind to the enzyme.
• Several models of activity
Enzymes Animation
Lock & Key Model
• Has static
active site
• Molecules
fit into
active site
where
chemical
change
occurs
Lock & Key Model Contd.
Induced Fit Model
• Often these
molecules are
flexible, and
change shape
when an
appropriate
molecule binds
to an active
site. This is
known as an
Induced Fit.
Factors effecting enzymes:
• Temperature - Most human
•
•
enzymes operate at 3540OC. At lower
temperatures, allosteric
changes cannot occur. At
higher temperatures,
proteins (enzymes) can be
denatured.
pH - Charged areas of an
enzyme can be effected by
[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
Enzyme Regulation:
• Enzymes are usually regulated by 3
mechanism
– Competitive Inhibition
– Non-competitive Inhibition
– Allosteric Indibition
Competitive Inhibition
• Another
substance
binds to the
active site,
preventing
the
substrate
from binding
there.
Non-competitive inhibition
• Another
substance
binds to the
enzyme, at a
site other than
the active site.
This blocks the
binding of the
regular
substrates
Allostery
• An Inhibitor or Activator binds to a separate allosteric site
on the enzyme, changing the shape of the enzyme, either
Inhibiting or activating it's function. Often the products
serve as inhibitors. This is known as Feedback inhibition