Metabolism , Energy and Life

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Metabolism , Energy and Life

• As a whole metabolism is concerned with managing
  the material and energy (nrg) resources of the
  cell. All of this is precisely managed
• There are several pathways.

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Anabolic Pathway

• Consume nrg to form build more complex molecules
  from simple ones.

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Energy is the capacity to do work.

• Animation Quizzes go to nrg conversion
• Kinetic energy is the energy of motion
• Potential nrg is the nrg that matter posses due
  to location or structure.
• Howstuffworks "Animation of the Day(go to roller
  coaster)

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Exergonic

• When the reactants of a chemical reaction have
  more free energy than the products of that
  reaction and energy is released, the reaction is
  said to be exergonic (-?H) heat releasing

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Endergonic

• On the other hand, if the products of a chemical
  reaction have more free energy than the reactants
  and the reaction requires an input of energy, the
  reaction is said to be endergonic (?H) heat
  absorbing

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Catabolic Pathway

• Release nrg by breaking down complex molecules to
  simpler compounds.

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Lifes chemical reactions are of two types

• 1. Endergonic reactions
• requires net input of energy.
• products have more potential energy than
  reactants (e.g. 6CO2 6H2O to C6H12O6)
• e.g. photosynthesis, anabolic reactions

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• 2. Exergonic reactions
• chemical reaction that releases energy.
• reactants have more potential energy in their
  covalent bonds than the products.
• e.g. catabolic reactions ( C6H12O6 to 6CO2
  6H2O)
• Burning and cellular respiration are examples of
  exergonic processes. However, burning is a 1 step
  process that releases energy all at once, whereas
  cellular respiration involves many steps, each a
  separate chemical reaction (i.e a slow burn).
• Exergonic and Endergonic Reactions

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Oxidation and reduction flow of energy in living
things.
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• Oxidation is the loss of an electron
• Reduction is the gain of an electron

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• Cellular respiration energy-releasing chemical
  breakdown of glucose molecules and the storage of
  the energy in a form that the cell can use to do
  work.
• Cellular metabolism sum of all exergonic and
  endergonic reactions in a cell.

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ATP and cellular work

• Chemical energy in the form of ATP powers nearly
  all cellular work.

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• Covalent bonds connecting second and third
  phosphate groups of ATP are unstable. These bonds
  can be readily broken (hydrolysis)

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• This reaction is highly exergonic and can be
  coupled to a endergonic reaction.
• Energy coupling involves transfer of third
  phosphate to another molecule.

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Work of the cell requires nrg and this is most
often provided by ATP

• 1. Mechanical work- such as the beating of cilia
• 2. Transport work pumping of substances across
  the cell membrane
• 3. Chemical work- the pushing of endergonic
  reactions which would not normally occur
  spontaneously.

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Work of the cell requires nrg and this is most
often provided by ATP

• 1. Mechanical work- such as the beating of cilia
• 2. Transport work pumping of substances across
  the cell membrane
• 3. Chemical work- the pushing of endergonic
  reactions which would not normally occur
  spontaneously.

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Enzymes. (When in doubt answer with enzymes)

• Enzyme protein molecule that serves as a
  biological catalyst.Enzymes allow life to go on.
  They speed up and regulate metabolic reactions.
  Enzymes are catalysts.
• Catalyst a chemical that speeds up the rate of
  a reaction without itself being consumed in the
  process.

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Enzymes. (When in doubt answer with enzymes)

• Enzyme protein molecule that serves as a
  biological catalyst.Enzymes allow life to go on.
  They speed up and regulate metabolic reactions.
  Enzymes are catalysts.
• Catalyst a chemical that speeds up the rate of
  a reaction without itself being consumed in the
  process.

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Activation energy

• Enzymes lower the barriers that normally prevent
  chemical reactions from occurring (or slow them
  down) by decreasing the required activation
  energy. Thus, in the presence of enzymes,
  reactions proceed at a faster rate.

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Enzymes are substrate specific
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Enzymes are substrate specific

• Substrate reactants in an enzyme catalyzed
  reaction.
• Each enzyme has a unique 3-D shape and recognizes
  and binds only the specific substrate of a
  reaction.
• Active site small portion of enzyme molecule
  which actually binds the substrate.

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The active site is the catalytic center.

• When the active site of an enzyme is unoccupied
  and its substrate is available the cycle begins
• An enzyme substrate complex forms with hydrogen
  and ionic bonds
• The substrate is converted to product
• The enzyme releases the product
• The enzyme is available for the next reaction
• Animation of Enzyme Reaction

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• Animation of Enzyme Action
• http//ull.chemistry.uakron.edu/genobc/animations/
  enzyme.mov

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Properties of active site

• Typically a grove or pocket on the protein
  (enzymes are proteins)
• The specificity of an enzyme is based on the fit
  between the active site and the substrate

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Properties of active site

• Acts as a template for substrate orientation.
• Stabilizes the transition state
• Provides a favorable microenvironment
• May participate directly in reaction

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The lock and Key model

• Lock and key

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Induced fit model

• Binding of the first substrate (gold) induces a
  conformational shift (angular contours) that
  facilitates binding of the second substrate
  (blue), When catalysis is complete, the product
  is released, and the enzyme returns to its
  uninduced state.

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Factors which may denature enzymes

• Each enzyme works best at a certain pH
• Altering the pH will denature the enzyme. This
  means that the structure of the enzyme is altered
  and the shape no longer works with its specific
  substrate

• CIEC Catalysis -- Principles of Catalysis

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• Temperature is another factor. Enzymes have
  specific temperature ranges. Most denature at
  high temperatures, but will continue to work at
  lower temperature.

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Enzymes they are very important.

• Biology I Interactive Animations go to (Enzyme
  Substrate Formation Hong Kong Bio Web
• One more look

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Enzyme Inhibition

• chemicals which interfere with enzyme function

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Competitive Inhibitors

• Mimics
• BBC Education - AS Guru - Biology - Biological
  Molecules - Proteins - Enzymes - Competitive
  Inhibitors
• New Page 1

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Non Competitive Inhibitors

• Bind to some other point on the molecule.
• BBC Education - AS Guru - Biology - Biological
  Molecules - Proteins - Enzymes - Non-competitive
  Inhibitors
• New Page 1

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Regulation of Enzymes

• Allosteric Enzymes The Life Wire Content
• (go to chapter 6 tutorial)

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Noncompetitive Inhibition with Allosteric Enzymes
or feedback inhibition

• When the end product (inhibitor) of a pathway
  combines with the allosteric site of the enzyme,
  this alters the enzyme's active site so it can no
  longer bind to the starting substrate of the
  pathway. This blocks production of the end
  product.