ENERGY

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ENERGY
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Energy

• capacity to perform work
• done when objects are moved against opposing
  forces things move in directions in which they
  would not have moved if left alone
• body needs energy
• cells are biggest users of energy in the body
• need energy to make complex molecules from
  monomer building blocks-anabolic reactions
• need energy to break down macromolecules-
  catabolic reactions to obtain energy to do all of
  the activities they need to do everyday

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First Law of Thermodynamics

• energy cannot be destroyed nor created
• energy can be converted from one form to another
• plants convert energy in sunlight into chemical
  energy that life forms can use to perform
  activities of life

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Forms of Energy

• Kinetic energy
• energy of motion
• Potential energy
• stored energy an object has as a result of its
  locomotion or structure

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Forms of Energy
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Energy Conversions

• energy can be converted from one type into
  another
• cannot be created or destroyed
• cant use energy over over because each time
  there is energy transfer some energy becomes
  unusable

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Second Law of Thermodynamics

• energy conversions generate heat
• kinetic energy
• from random movement of atoms molecules
• difficult to reuse to perform work
• lost to surroundings
• energy of aimless molecular movement
• measure of disorder or randomness
• amount of disorder in a system is entropy
• Second Law of Thermodynamics
• energy conversions increase entropy in a system
  reduce order

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Energy Flow

• energy flows into our ecosystem as sunlight
• kinetic energy (from sun) is transformed into
  chemical energy-potential energy of food fuels
  by photosynthesis

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Energy Flow

• animals consume food products to provide ATP or
  energy for cells to perform work

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Endergonic Reactions

• yield potential energy
• require input of energy
• products acquire more energy than reactants
• energy is stored in covalent bonds of products
• photosynthesis is an endergonic reaction

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Exergonic Reactions

• release energy
• reactions begin with reactants whose covalent
  bonds contain more energy than those in products
  release energy to the environment
• occur in cells of body
• cellular respiration
• oxygen is used to convert chemical energy stored
  in fuel molecules (glucose) to chemical energy
  (ATP) cell uses to carry on its processes
• Glucose O2 ?CO2 H2O

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ATP-Adenosine Triphosphate

• provides energy for cellular work
• consists of
• adenine
• nitrogenous base
• ribose
• five carbon sugar
• called adenosine
• 3 PO4 groups attached-triphosphate part
• phosphate bonds are unstable
• can be easily broken by hydrolysis in exergonic
  reactions
• each PO4 group released from ATP yields 7Kcal of
  energy
• one phosphate group removed
• ATP?ADP pi 7Kcal of energy
• adenosine diphosphate inorganic phosphate
  energy
• another phosphate removed
• AMP pi 7Kcal of energy
• adenosine monophosphate

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Cellular Metabolism

• every working cell in body performs exergonic
  endergonic reactions
• sum-cellular metabolism
• energy released from exergonic reactions is used
  to drive endergonic reactions
• energy coupling
• ATP functions in energy coupling

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Energy Coupling
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Factors in Chemical Reactions

• many molecules in body store tremendous amount
  of potential energy
• do not spontaneously break down into smaller
  components
• to initiate reactions reactants need to overcome
  an energy barrier
• amount of energy that a compound must absorb
  before a chemical reaction can begin-activation
  energy
• requires a catalyst
• something to speed rate of a reaction

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Enzymes

• speed rate of reactions
• lower activation energy
• globular proteins
• names typically end in ase
• each has a unique 3-D shape
• shape determines which reactions enzyme can
  catalyze

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Enzymes

• specific reactant for specific enzyme-substrate
• fits into specific area-active site
• once product forms
• enzyme detaches from active site
• free to start another reaction

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Enzyme Action
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Saturation Limit

• reaction rate is proportional to concentration of
  substrate concentration of enzyme
• enzyme must meet with specific amount of
  substrate before catalysis can begin
• higher substrate concentrations? more frequently
  encountered by enzyme
• when substrate concentrations are high enough so
  every enzyme molecule is cycling through its
  reaction sequence at top speed? further increase
  in substrate concentration will not effect rate
  of reaction unless more enzyme is added
• substrate concentration at which rate of a
  reaction is maximum is saturation limit

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Regulation of Enzymatic Reactions

• many variables turn enzymes on off to control
  reaction rates
• enzymes are proteins
• protein shapes can be changed by the environment
• Temperature
• Salt concentration
• pH

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Regulators of Enzymatic Activity

• Cofactors
• important in enzyme function
• ions or molecules that bind to an enzyme before
  substrate can bind
• allows enzymes to be active sometimes inactive
  at other times
• several important inorganic cofactors-zinc, iron
  copper
• organic cofactors are coenzymes
• most made from vitamins or are vitamins

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Inhibition of Enzymatic Activity

• chemicals that interfere with enzyme function are
  inhibitors
• competitive inhibitors
• fit into active sites so real substrate cannot
• noncompetitive inhibitors
• bind at sites other than active site
• changes enzymes shape
• causes active site to no longer recognize
  substrate

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Inhibition

• Reversible inhibitors
• can serve a regulatory function
• turn enzyme on when needed
• turn it off when not
• Irreversible inhibitors
• kill enzyme function
• poisons
• block metabolic processes that are essential to
  survival

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Irreversible Inhibition

• Penicillin
• inhibits enzymes in bacteria needed to make cells
  walls
• since humans do not have this enzyme penicillin
  can be used to kill the bug without effecting
  human cells