The Hindenberg

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The Hindenberg
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The Crash

• The famous German-built 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.

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Hydrogen

• Hydrogen gas, because it is lighter than air,
  floats upward in the atmosphere. People once used
  it to lift zeppelins and other airships into the
  sky, allowing trans-Atlantic 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
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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.

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Endergonic Reaction

• Endergonic Reaction - One in which energy must be
  supplied for the reaction to occur (products have
  more chemical energy than reactants)

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Catalyzed Reaction

• 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.

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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

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Enzymes Animation
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Lock Key Model

• Has static active site
• Molecules fit into active site where chemical
  change occurs

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Lock Key Model Contd.
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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.

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Factors effecting enzymes

• Temperature - Most human enzymes operate at
  35-40OC. 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

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Enzyme Regulation

• Enzymes are usually regulated by 3 mechanism
• Competitive Inhibition
• Non-competitive Inhibition
• Allosteric Indibition

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Competitive Inhibition

• Another substance binds to the active site,
  preventing the substrate from binding there.

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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

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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