ENERGY

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• ENERGY METABOLISM

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Properties/ Characteristics of Enzymes

• Are organic catalysts which change the
• RATE of a chemical reaction
• 2. All are globular proteins

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Properties/ Characteristics of Enzymes

• 3. Some enzymes depend upon COENZYMES to
  catalyze the reaction (ex NAD, NADP, FAD)
• 4. Coenzymes are organic molecules
• (B vitamin derivatives) which assist a
  specific enzyme in a specific reaction

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Properties/ Characteristics of Enzymes

• 5. Are temperature
• sensitive-- they work
• most efficiently at an
• optimum
• temperature
• 6. Most are denatured at
• temperatures
• above 42o C

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Properties/ Characteristics of Enzymes

• 7. Are pH sensitive- most react between pH
  6-8, except for gastric enzymes
• 8. Enzymes are specific to a given substrate

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Properties/ Characteristics of Enzymes

• 9. Possesses an ACTIVE SITE which reacts with a
  specific substrate
• 10. Able to catalyze reversible reactions--
• direction of these reactions depends
• upon substrate concentrations

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Properties/ Characteristics of Enzymes

• 11. Lower the activation
• energy of the
• reaction
• 12. Each has a given
• TURN-OVER number
• (ex molecular activity
• of catalase is
• 5.6 x 106 molecules
• of H2O2
• transformed/minute)

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Properties/ Characteristics of Enzymes

• 13. Some enzymes require COFACTORS? metals
  essential to the enzymatic reaction
• (ex catalase requires Fe2 or Fe3)
• 14. Are unaltered by the reaction they catalyze
  and thus are REUSABLE

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Figure 2-21 Enzyme Action
Enzyme Sucrase In Action
Section 2-4
Enzyme (hexokinase)
Glucose
Substrates
ADP
Products
Glucose-6- phosphate
ATP
Products are released
Active site
Substrates bind to enzyme
Enzyme-substrate complex
Substrates are converted into products
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Energy Living Things
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Energy

• ENERGY will cause matter to move or change
• Ex mechanical, light, sound, heat, electrical,
  nuclear
• 1. Forms
• 1) POTENTIAL (stored)/ ex sugar cube,
  gasoline
• - Chemical energy
• 2) KINETIC (motion)/ ex heat, light,
  falling water (position)

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Cont. Energy

• 2. Thermodynamics energy conversion/
  transformations 
• 1) 1st Law Energy is not created or destroyed-
• only changed from one form to another
• (converted)
• Ex Food (chemical energy) ? Cell work
  (heat)
• 2) 2nd Law Entropy/Disorder- energy is lost
  to maintain order and changing trophic
  levels

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Cont. Energy

• 3. Energy Flow in Ecosystems (Unidirectional)
• Sun ? Inorganic Chemicals ----? Autotrophs----?
  Heterotrophs----? Heat
• HEAT (photosynthetic/
  HEAT (cellular respiration)
• chemosynthetic)
• Open System Can exchange energy matter with
  its surroundings (Earth)
• Organisms are open systems? absorb E (light
  E/chem E in form of organic molecules) releases
  heat and metabolic waste products to surroundings
• 2) Energy in living systems is moved by a
  transfer of electrons from one atom to another

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Cont. Energy Flow in Ecosystems

• 3) Reactions that pass electrons are called
  OXIDATION-REDUCTION REACTIONS
• (Pass e- from one atom to another)
• OXIDATION removal of electrons (loss) e- or H2
  
• REDUCTION addition of electrons (gain) e- or H2
• OIL RIG
• Na Cl ? Na Cl-

Becomes oxidized (lose e-)
Becomes reduced (gain e-)
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Cont. Energy Flow in Ecosystems

• 4) In chemical reactions, oxidation and reduction
  occur simultaneously- if one molecule gains an
  electron (reduction), then a 2nd molecule loses
  the electron (oxidation)? COUPLED REACTION

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Cont. Energy Flow in Ecosystems

• 5) How to determine if organic molecules are
  oxidized/reduced
• REDUCTION of C-H bonds increases
• OXIDATION of C-H bonds decreases
• Ex Respiration
• C6H12O6 6 O2 ? 6 CO2 6 H2O energy

Becomes oxidized (loses)
Becomes reduced (gains)
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Chemical Reactions

• B. CHEMICAL REACTIONS absorb or release energy
• 1) Endergonic needs or uses energy
• (energetically unfavorable reaction)
• Ex photosynthesis, building proteins
• - Non-spontaneous rxn
• 2) Exergonic gives off or releases energy
• (energetically favorable reaction)
• Ex respiration, fermentation, burning
• - Spontaneous rxn
•  

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Figure 2-19 Chemical Reactions
Chemical Reactions
Section 2-4
Endergonic Reaction
Exergonic Reaction
Energy-Releasing Reaction
Energy-Absorbing Reaction
Activation energy
Products
Activation energy
Reactants
Reactants
Products
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Cont. Chemical Reactions

• 3) The energy that drives reactions is called
  free energy? reactions releasing free energy can
  do cell work
• 4) Reactions start with reactants and form
  products

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Cont. Chemical Reactions

• 5) When fuel (glucose) is oxidized, enzyme
  reactions ensure that much of the free energy
  released is captured in the form of ATP rather
  than being released wastefully as heat to the
  environment
•  
• 6) This is called a coupled reaction? energy
  released from one reaction can be used to drive a
  reaction needing energy/ coupling reactions
  requires enzymes and cells conserve energy by
  coupling exergonic with endergonic reactions

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Cont. Chemical Reactions

• 7) Enzymes that catalyze cell endergonic
  reactions have two active sites
• a. for reactant b. for ATP

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Figure 2-21 Enzyme Action
Section 2-4
Enzyme (hexokinase)
Glucose
Substrates
ADP
Products
Glucose-6- phosphate
ATP
Products are released
Active site
Substrates bind to enzyme
Enzyme-substrate complex
Substrates are converted into products
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Coupled Reactions

• EXERGONIC GLUCOSE
  ENDERGONIC
• C
• ENERGETICALLY FAVORABLE ATP
  ENERGETICALLY UNFAVORABLE
• - energy released - energy
  needed
• - can create disorder
  P -
  creates order
• PRODUCTS HAVE LESS ADP
  PRODUCTS CONTAIN MORE
• ENERGY THAN REACTANTS D
  ENERGY THAN REACTANTS
• CO2 H2O

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Coupled Reactions

• Coupled reactions form activated/carrier energy
  molecule
• 1) Stores energy in small packets easy to
  exchange (ATP, NADH, NADPH), which are
• specialized to carry electrons and hydrogen
  atoms
• 2) Cells use activated energy carrier
  molecules like using money to pay for reactions

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Cont. Coupled Reactions

• 3) Most important and most abundant universal
  carrier is ATP
• But NADPH works with enzymes that catalyze
  anabolic reactions? supplying energy to build
• While NADH works with enzymes that catalyze
  catabolic reactions? moving energy from food to
  make ATP

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Cont. Coupled Reactions

• 4) COENZYMES organic molecules which transfer
  electrons from enzyme to organic
• molecule then coenzyme carries electrons to
  another enzyme which catalyzes a
• different reaction
• 5) Hydrogen atoms and electrons are stripped from
  food and join
• NAD ? NADH ? makes ATP

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Electron Carrier Molecules
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Metabolic Pathways

• D. METABOLIC PATHWAYS chains, branching chains,
  or cycles
• 1) A set of enzymes working in a very precise
  orderly series of reactions that converts
  molecule A into molecule F
• Molecule Molecule Molecule Molecule
  Molecule Molecule
• A ? B ? C
  ? D ? E ? F
• Enzyme 1 Enzyme 2 Enzyme 3
  Enzyme 4 Enzyme 5

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Cont. Metabolic Pathways

• 2) BIOSYNTHETIC PATHWAYS (Anabolic)
• Small building blocks ? Complex macromolecules
• Ex photosynthesis, building proteins)
• Endergonic rxn (uphill rxn)
•  3) DEGREDATIVE PATHWAYS (Catabolic)
• Complex macromolecules? Small building blocks
• Ex respiration, fermentation, digestion)
• Exergonic rxn (downhill rxn)

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Cont. Metabolic Pathways

• 4) VARIOUS PARTICIPANTS IN THESE PATHWAYS (Terms)
• Substrates reactants
• Intermediates produced in between
• End products substances remaining at end
• Energy carriers transfers energy (usually
  electrons/Hydrogen atoms)
• Enzymes catalyze reactions
• Coenzymes/cofactors help enzymes carriers
• Transport proteins in membrane/changing
  concentrations, influence direction of reaction

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Biochemical Pathway Glycolysis
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Cont. Metabolic Pathways

• 5) Enzymes direct metabolism in cells
• ? in enzyme concentration causes ? in reaction
  rate
• (to a point, then rate will
  level)
• ? in substrate concentration causes ? in
  reaction rate
•  
•  Rxn
• Rate
  
• _____________________
• ENZYME CONCENTRATION ?

Rxn Rate
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Metabolism

• E. METABOLISM Summary
• Dehydration synthesis
• building, endergonic
• BIOSYNTHESIS
• ANABOLISM
•  
• 
  -P
•  
• MACROMOLECULES ADP
  ATP BUILDING BLOCKS
•  
• Carbohydrate?
  P Glucose?
  CHO
• Glucose
• CATABOLISM
• 
  DEGRADATION
• 
  Hydrolysis
• 
  breakdown, exergonic
• 
  ex cell respiration, fermentation

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Cont. Metabolism

• 1) Built into each living cell are controls over
  its enzyme activity
• 2) By coordinating its control mechanisms, the
  cell maintains, increases, or decreases
  concentrations of substances controls can switch
  on or inhibit enzymes that are already made
• 3) ALLOSTERIC CONTROL enzymes that have already
  been formed can be activated or inactivated when
  a signal substance combines at a binding site
  other than the active site and causes shape
  changes to the active site

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Cont. Metabolism

• 4) Biochemical pathways may be controlled by
  FEEDBACK INHIBITION shutting down
• of a biochemical pathway due to allosteric
  enzyme sensitivity to product concentration
• 5) ALLOSTERIC ENZYME enzyme that changes shape
• has two binding sites 1) active site 2)
  allosteric site
• signal molecule binds to enzyme allosteric site
  and will activate or deactivate an enzyme

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Cont. Allosteric Enzyme

• ALLOSTERIC SIGNAL -------------? ACTIVE
  (binds to substrate)
• ENZYME MOLECULE
  ENZYME
• PRESENT
•  
• ALLOSTERIC SIGNAL -------------?
  INACTIVE (cannot bind to
• ENZYME MOLECULE
  ENZYME substrate)
• ABSENT

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Allosteric Enzyme
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Cont. Metabolism

• 6) How a product (concentration) can inactivate
  an enzyme that normally makes the product in a
  metabolic pathway
• Enzyme A Enzyme B Enzyme
  C
• 1 --------------? 2 --------------? 3
  -------------? 4
• Enzyme A is the allosteric enzyme and has the
  allosteric site shape of the product (4), which
  blocks substance 1 from beginning the metabolic
  pathway
• ? product concentration Enzyme inactive
  (inhibition)
• ? product 4 acts as the signal molecule

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Feedback Inhibition