Metabolism

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Metabolism
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Metabolism

• Metabolism anabolism catabolism
• In a reaction, bonds between reactants break down
  and bonds between products form.
• Energy is absorbed when reactant bonds break
  (endothermic).
• Energy is released when product bonds form
  (exothermic).

Drew's Metabolism Animation - Science is a Verb!
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Catabolic Reactions

• Breakdown of complex substances.
• Examples
• Break starch into glucose molecules
• Break glucose into carbon dioxide and water

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Anabolic Reactions

• Build complex substances from smaller subunits.
• Examples
• Protein is built from joining amino acids.

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• Metabolism Anabolic Catabolic reactions
• It is essential for living organisms to survive
  and it requires
• ENERGY

Annie's 20 Animations - Science is a Verb!
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Energy

• The ability to do work.
• Kinetic energy in motion
• Potential stored energy
• When energy is transferred from one place to
  another that is called WORK

Energy Transformation on a Roller Coaster
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1st Law of Thermodynamics

• Energy is constant. It cannot be created or
  destroyed, only converted from one form to
  another. If an object gains energy, it does so at
  the expense or a loss in energy somewhere else in
  the universe.

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Bond Energy

• Measure of the stability of a covalent bond. (kJ)
  
• Equal to the min energy required to break one
  mole of bonds between two types of atoms.
• Equal to the amount of energy released when a
  bond is formed.

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Potential Energy Diagrams

• Shows the change in potential energy during a
  chemical reaction.

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http//www.mhhe.com/physsci/chemistry/essentialche
mistry/flash/activa2.swf
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Metabolism

• Activation Energy
• The amount of energy needed to break the
  reactants bonds.

The change in energy that occurs is called heat
or enthalpy (?H)
Endothermic ?H
Exothermic ?H -
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• Activation Energy
• Energy needed to break bonds and is equal to
  the difference between the potential energy level
  of the transition state and the potential energy
  of the reactants.

• Transition State
• Bonds within reactants are breaking (require
  energy) and the bonds between products are
  forming (release energy).

The Cell Online Chapter 3 - Animations
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Spontaneous Reactions

• Exothermic reactions tend to occur spontaneously
  since products are MORE stable then reactants.
• Why would endothermic reactions occur if the
  products are LESS stable than the reactants?
• ENTROPY also needs to be considered.

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Entropy

• A measure of the randomness of disorder in a
  collection of objects or energy notated as S.
• The universe favors an increase in entropy.
• Examples
• Deck of cards falling and scattering
• Dropping a glass and shattering it
• Diffusion

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http//www.wwnorton.com/college/chemistry/gilbert/
tutorials/ch13.htm
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Spontaneous vs Non-spontaneous
Exothermic Rxns (favoured) Endothermic Rxns (Not favoured)
Increase in Entropy (favoured) Spontaneous at all temperatures Not spontaneous at low temp. Spontaneous at high temp.
Decrease in Entropy (not favoured) Not spontaneous at high temp. Spontaneous at low temp. Not spontaneous at all temperatures. Proceeds only with a net input of energy.
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Free Energy

• Energy that is available to do work.
• Also known as Gibbs free energy.
• ?G G(final) G(initial)
• Exergonic Reactions Spontaneous and involves a
  decrease in Gibbs free energy, ?G is negative
• Endergonic Reactions Not Spontaneous and
  involves an increase in Gibbs free energy ?G is
  positive

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The Laws of Thermodynamics

• First Law
• The total amount of energy in the universe is
  constant. Energy cannot be created or destroyed,
  but only converted from one form into another.
• Second Law
• Every energy transfer or transformation increases
  the entropy of the universe.

Entropy is a measure of the randomness or
disorder in energy or in a collection of objects.
Random, useless energy that cannot do work,
e.g., heat.
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2nd Law of Thermodynamics

• Also known as the law of entropy.
• The entropy of the universe increases with any
  change that occurs ?S(universe) gt 0

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Metabolic Reactions are Reversible

• When a reversible reaction reaches equilibrium ?G
  value is zero and its free energy is zero.
• A cell whose reversible reactions have reached
  equilibrium is a dead cell.

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ATP Adenosine Triphosphate

• Primary source of free energy in living cells
• ATPase catalyzes the hydrolysis of the terminal
  phosphate
• Releases 31kJ/mol of energy
• Terminal phosphate is instable due to negative
  charges.
• Energy produced is use to attach phosphate group
  to another molecule (phosphorylation)

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Adenosine Triphosphate (ATP)

• ATP is a nucleotide consisting of adenine, ribose
  and 3 phosphate groups.

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Adenosine Triphosphate (ATP)

• ATP drives all cellular reactions by providing
  the energy that is needed.

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Redox Reactions

• Chemical reactions involving the transfer of one
  or more electrons from one atom to another.
• Reducing Agent The substance that loses an
  electron.
• Oxidizing Agent The substance that gains an
  electron.

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Redox Reactions

• Coenzymes are important in the creation of ATP.
• Working with special enzymes, coenzymes accept
  electrons and transfer them to other molecules.
• As oxidizing enzymes remove electrons from a
  substrate (oxidation) they pass them onto a
  coenzyme (reduction).
• Therefore the substrate loses electrons
  (oxidized) and the coenzyme gains electrons
  (reduced).
• When the reduced coenzyme passes the electron to
  another substrate, the coenzyme loses electrons
  (oxidized) and the substrate gains electrons
  (reduced).
• Coenzymes can carry electrons from one redox
  reaction to another.