Download AEROBIC RESPIRATION

In the name of GOD
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Bioenergetics
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Biological
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Definition asa
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 Bioenergetics
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 Energy Changes in Biochemical
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Reaction
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 – Converting
foodstuffs (fats,
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proteins,
carbohydrates) into
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energyo
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Metabolism asa
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 Metabolism is definedi as the total
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of all cellular reactions
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 that occur in the body; this
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includes both
the synthesis of
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 molecules
and the breakdown of
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molecules.
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Isothermic Reactions
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 In Non-Biological systems:
Heat
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energy is used for hperforming work.
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 In Biological
Systems: Chemical
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n Heat energy) is used for
energyo(no
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all biochemical
reactions.
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…Isothermic Reactions
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 Energy conserved in Living
organisms:
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By
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Oxidation to metabolic
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Stored as the high-energy
bond of ATP
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Provide energy
for biological process
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Muscle contraction,
active ion transport
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Thermodynamic alaws
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 Interconvert different forms
of energy
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and exchange with their
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 1st Law: Energy can neither be created
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nor be destroyed.
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It meansnenergy
just converting
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 2 Law:
In spontaneous reactions the
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total
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Overview of Bioenergetics
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 Metabolism
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 – Sum of all chemical reactions
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that occur in A
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 – Anabolic h
reactions
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Synthesis
of molecules
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 – Catabolic
reactions
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r.Breakdown of molecules
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Gibbs Free Energyasa(ΔG)
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 Energy available for useful
work
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ΔG=ΔH- TΔS A
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ΔH= Changes
in
enthalpy
or
heat
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T= Temperature
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ΔS=Changes
in entropy
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Gibbs Free Energy
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 Negative ΔG=Exergonic
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 Positive
ΔG=Endergonic
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 ΔG=0
Equilibrium state
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Standard Free Energy
ΔG0
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 ΔG0=-RT LnKeq n
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 A+B
C+D
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 Keq= Co* D/ A*B
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Metabolic reactions
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Endergonic reactions
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– Require energy to beaadded
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– Endothermic
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• Exergonic reactions
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– Release energy
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– Exothermic
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• Couplednreactions
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– Liberation
of energy in an exergonic
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reaction
.r drives
an
D endergonic reaction
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Coupled Reactions
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Oxidation-Reduction
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Reactions asa
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Oxidation
– Removing an electron
• Reduction
– Addition of an electron
• Oxidation and reduction are always coupled
reactions
• Often involves the transfer of hydrogen atoms
rather than free electrons
– Hydrogen atom contains one electron
– A molecule that loses a hydrogen also loses an
electron and therefore is oxidized
• Importance of NAD and FAD
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Oxidation Reaction sab
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The loss of electrons from
n a substance.
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 Or the gain of oxygen.
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C6H12O6 o
+n6O2 6CO2 + 6H2O +
energy
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Oxidation
glucose
copyright cmassengale
ATP
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Reduction Reaction sab
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The gain of electronsnto a
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substance.
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Or the loss of oxygen.
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o2 
C6H12O6 + 6O
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Reduction
6CO2 + 6H2O + energy
glucose
copyright cmassengale
ATP
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Oxidation-Reduction Reaction
Involving
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NAD and NADH as
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High-Energy Phosphates
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Adenosine triphosphate (ATP)
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– Consists of adenine, ribose,
and three
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linked
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phosphates
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• Synthesis h
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• Breakdown
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ADP + Pi n ATP
o + Energy ATP ATPase
ADP + Pi
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High-Energy
Phosphates
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High-Energy
Phosphates
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Structure of ATP
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Bioenergetics
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Formation of ATP n
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– Phosphocreatine
(PC) breakdown
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– DegradationAof glucose and
glycogen eh
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Glycolysis
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Oxidative
M formation of ATP
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Formation of ATP
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 Anaerobic pathways i
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 – Do not involve O2
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 – PC breakdown
A and glycolysis
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 Aerobic pathways
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 – Require
O2
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 – Oxidative
phosphorylation
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Anaerobic ATP Production
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ATP-PC system
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– Immediate source ofaATP
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• Glycolysis
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– Glucose
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pyruvic acid or 2 lactic acid
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– Energy investment
phase
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Requires
2 ATP
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– Energy
generation phase
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Produces
4 ATP, 2 NADH, and 2
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pyruvate
or 2 lactate
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AEROBIC RESPIRATION
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4 STAGES:
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
cytoplasm
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Glycolysis
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Mitochondrial
Link reactionh
matrix
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Kreb’soCycle
Mitochondrial
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Oxidative
Mitochondrial
Phosphorylation
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2.
3.
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inner membrane
(cristae)
The Two Phases Glycolysis
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Glycolysis: Energy
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Investment Phase
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Hydrogen and Electron
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Carrier Molecules
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Transport hydrogens and associated
electrons
– To mitochondria for ATP generation
(aerobic)
– To convert pyruvic acid to lactic acid
(anaerobic)
• Nicotinamide adenine dinucleotide (NAD)
• Flavin adenine dinucleotide (FAD)
NAD + 2H+
NADH + H+
FAD + 2H+
FADH2
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A Closer Look
NADH is “Shuttled” into
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Mitochondriaasa
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NADH produced in glycolysis
must be
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converted
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back to NAD
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– By converting pyruvic
acid to lactic acid
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– By “shuttling”
H+ into the mitochondria
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• A specificirtransport system shuttles H+
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across the
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mitochondrial
membrane
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– Located in the mitochondrial membrane
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Aerobic ATP Production
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Krebs cycle (citric acid cycle) i N
– Pyruvic acid (3 C) is converted
to acetyl-CoA (2
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C)
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CO2 is given off
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– Acetyl-CoA combines with oxaloacetate (4 C) to
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form citrate (6 C)
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– Citrate is metabolized
to oxaloacetate
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Two CO2 molecules
given off
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– Produces
three molecules of NADH and one FADH
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– Also forms one molecule of GTP
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Produces
one ATP
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The Three Stages of
Oxidative
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Phosphorylation
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The Krebs Cycle
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Regulation of CAC:
Rate controlling enzymes:
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Isocitrate dehydrogenase
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a-keoglutaratedehydrogenase
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Regulation of activity by:
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Substrate availability
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Product inhibition
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Allosteric inhibition
or
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Citrate synthatase
activation by other
intermediates
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Aerobic ATP Production
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Electron transport chain
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– Oxidative phosphorylation occurs
in the
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mitochondria
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– Electrons removed from
NADH and FADH are
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passed along a series
of carriers (cytochromes) to
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produce ATP
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Each NADH r
produces
2.5 ATP
Each FADHiproduces 1.5 ATP
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– Called the
o chemiosmotic hypothesis
– H+ from
NADH and FADH are accepted by O2 to
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.water
form
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Bioenergetics
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Oxidative Phosphorylation:b
Electron transport chain
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located on the membranes of the cristae of the
mitochondria.
The membranes contain a series of proteins, which are
involved in the electron transport chain.
Electrons are supplied in the form of reduced NAD and
reduced FAD, which pass from the Krebs cycle in the
matrix to the cristae.
Electrons are passed from one protein to the next in a
series of Redox reactions.
At each transfer energy from the electrons is used to
make ATP.
The products of this process are low energy electrons
and protons. Protons bind with oxygen to form water,
and a total of 38 ATP molecules are generated.
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Oxidative phosphorylation
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 Also known as:
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Terminal oxidationja
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The electron transport
chain
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 A series of carrier molecules that
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transfer electrons
along
a
chain
,
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producing
ATP
in
the
process.
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 The M
electrons come from the
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hydrogen atoms released from
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Kreb’s
cycle
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Water is produced
The Chemiosmotic
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Hypothesis of ATP Formation
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Electron transport chainnresults in
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pumping of H+
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ions across innerAmitochondrial
membrane h
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– Resultsnini H+ gradient across
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membrane
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• Energy
r. released to form ATP as H+
D diffuse
ions
back across the membrane
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Sequence of Electron
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Carriers
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Sequence of Electron
Carriers
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Site of action of some inhibitors of
electron transport
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Inhibits electron flow in Complex I
Prevents the utilization of NADH as a substrate.
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Inhibits electron flow from Cyt bH
Cyanide (CN-), azide (N3- )
react with the ferric (Fe3+ ) form of heme a3.
Carbon monoxide (CO):
Inhibits the ferrous (Fe2+) form.
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Stage Location Reactants
Glycolysis
Link
reaction
Kreb’s
cycle
Ox phosp
Cytosol
Glucose, ATP,
NAD
Phosphorylation,
oxidation, gain of
2ATP
Acetyl coenzyme A,
carbon dioxide,
NADH
Decarboxylation,
oxidation
Acetyl coenzyme A, 4C
compound,
NAD, FAD, ADP
NADH, FADH,
carbon dioxide,
ATP
Oxidation,
decarboxylation,
gain of 1ATP
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Hydrogen from
NADH
ATP, water, NAD
Oxidation,
phosphorylation
Mitochondrial
cristae
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Other
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Pyruvate,
NADH, ADP,
ATP
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Mitochondrial Pyruvate, NAD,
matrix
coenzyme A
Mitochondrial
matrix
Products
In Cytosol
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In Mitochondria
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Control of Bioenergetics
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Rate-limiting enzymes
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– An enzyme that regulates
a the rate of a
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metabolic
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pathway
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• Modulators of h
rate-limiting enzymes
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– Levels of ATP
and ADP+Pi
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High levels
o of ATP inhibit ATP production
Low
levels of ATP and high levels of ADP+Pi
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r. ATP production
stimulate
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Example of a Rate-Limiting
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Enzyme
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Study Questions
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Briefly explain the concept of coupled reactions.
3. Define the following terms:
(1) bioenergetics,
(2)endergonic reactions, and
(3) exergonic reactions.
4. Discuss the role of enzymes as catalysts. What is
meant by the expression “energy of activation”?
5. Where do glycolysis, the Krebs cycle, and
oxidative phosphorylation take place in the cell?
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…Study Questions
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7. What are the high-energy phosphates? Explain
the statement that “ATP is the universal energy
donor.”
8. Define the terms aerobic and anaerobic.
9. Briefly discuss the function of glycolysis in
bioenergetics. What role does NAD play in
glycolysis?
10. Discuss the operation of the Krebs cycle and the
electron transport chain in the aerobic production
of ATP. What is the function of NAD and FAD in
these pathways?
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Thanks for your attention
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