biology-respiration- chapter 8
TRANSCRIPT
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CHAPTER 8CHAPTER 8
RESPIRATIONRESPIRATION
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8.1 ATP8.1 ATP (Adenosine Triphosphate)(Adenosine Triphosphate)
Immediate energy source that drivesImmediate energy source that drivesmost cellular work.most cellular work.
Cells do this work byCells do this work by energyenergy
couplingcoupling
- uses an- uses an
exergonicexergonic
process to drive anprocess to drive an endergonicendergonic one.one.
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Endergonic ReactionEndergonic Reaction - ends with- ends with netnet
gain
gain in energyin energy
Products have more energy thanProducts have more energy than
reactants, e.g., photosynthesisreactants, e.g., photosynthesis
Exergonic ReactionExergonic Reaction - ends with- ends with netnet
lossloss in energyin energy
Reactants have more energy thanReactants have more energy thanproducts, e.g., cellular respirationproducts, e.g., cellular respiration
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Structure and hydrolysis of ATPStructure and hydrolysis of ATP
ATP = Nucleotide with unstableATP = Nucleotide with unstable
phosphate bonds that cell hydrolyzesphosphate bonds that cell hydrolyzes
for energy to drive endergonicfor energy to drive endergonicreactions.reactions.
Consists of adenine, ribose, & chainConsists of adenine, ribose, & chain
of three phosphate groups.of three phosphate groups.
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Unstable bonds between phosphateUnstable bonds between phosphate
groups can be hydrolyzed in an exergonicgroups can be hydrolyzed in an exergonic
reaction.reaction.
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When terminal phosphate bond isWhen terminal phosphate bond is
hydrolyzed, a phosphate group ishydrolyzed, a phosphate group isremoved producing ADP (adenosineremoved producing ADP (adenosine
diphosphate).diphosphate).
ATP + HATP + H22OO
ADP + PADP + P iiUnder standard lab conditions, reactionUnder standard lab conditions, reaction
releases -31 kJ/mol (-7.3 kcal/mol).releases -31 kJ/mol (-7.3 kcal/mol).
In living cell, reaction releases -55In living cell, reaction releases -55kJ/mol (-13 kcal/mol) - 77% more thankJ/mol (-13 kcal/mol) - 77% more than
under standard conditions.under standard conditions.
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Terminal phosphate bonds of ATPTerminal phosphate bonds of ATP
are unstable, so:are unstable, so:
Products of hydrolysis reaction areProducts of hydrolysis reaction are
more stable than reactants.more stable than reactants.Hydrolysis of phosphate bonds isHydrolysis of phosphate bonds is
thus exergonic as system shifts to athus exergonic as system shifts to a
more stable state.more stable state.
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How ATP performs workHow ATP performs work
Exergonic hydrolysis of ATP coupledExergonic hydrolysis of ATP coupledwith endergonic processes - phosphatewith endergonic processes - phosphate
group transferred to another molecule.group transferred to another molecule.
Phosphate transfer enzymaticallyPhosphate transfer enzymaticallycontrolled.controlled.
Molecule receiving phosphateMolecule receiving phosphate
(phosphorylated/activated(phosphorylated/activatedintermediate) becomes more reactive.intermediate) becomes more reactive.
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The regeneration of ATPThe regeneration of ATP
ATP continually regenerated by cell.ATP continually regenerated by cell.
Rapid process: 10Rapid process: 1077 molecules used andmolecules used andregenerated/sec/cell).regenerated/sec/cell).
Reaction: endergonic.Reaction: endergonic.
ADP + PiADP + Pi ATPATP G = + 31 kJ/mol (+7.3 kcal/mol)G = + 31 kJ/mol (+7.3 kcal/mol)
Energy to drive endergonic regenerationEnergy to drive endergonic regenerationof ATP comes from exergonic process ofof ATP comes from exergonic process ofcellular respiration.cellular respiration.
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8.2 Aerobic Respiration8.2 Aerobic Respiration
Preview of cellular respirationPreview of cellular respiration(See Figure 9.6, Campbell, page 164)(See Figure 9.6, Campbell, page 164)
Stages of respiration:Stages of respiration:i.i. GlycolysisGlycolysis
ii.ii. Citric acid cycleCitric acid cycle
iii.iii. Electron transport chain (ETC)Electron transport chain (ETC)
iv.iv. Oxidative phosphorylation.Oxidative phosphorylation.
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GlycolysisGlycolysis - in cytoplasm.- in cytoplasm.
Glucose broken down into twoGlucose broken down into twomolecules of pyruvate.molecules of pyruvate.
Citric acid cycleCitric acid cycle - in mitochondrial- in mitochondrialmatrix.matrix.Completes breakdown of glucoseCompletes breakdown of glucose
by oxidizing a derivative of pyruvateby oxidizing a derivative of pyruvateto COto CO
22..
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Several steps in glycolysis and citricSeveral steps in glycolysis and citricacid cycle areacid cycle are redoxredox reactions -reactions -
dehydrogenase enzymes transferdehydrogenase enzymes transfer
electrons from substrates to NADelectrons from substrates to NAD++,,forming NADH.forming NADH.
NADH passes electrons to ETC.NADH passes electrons to ETC.
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Electrons then move from molecule toElectrons then move from molecule tomolecule until they combine withmolecule until they combine with
molecular Omolecular O22and Hand H++ to form water.to form water.
As they passed along chain, energyAs they passed along chain, energycarried by electrons is used tocarried by electrons is used to
synthesize ATP in mitochondrion viasynthesize ATP in mitochondrion via
oxidative phosphorylationoxidative phosphorylation..
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Inner membrane of mitochondrion isInner membrane of mitochondrion issite of electron transport chain (ETC)site of electron transport chain (ETC)
and chemiosmosisand chemiosmosis
ETC + Chemiosmosis = OxidativeETC + Chemiosmosis = OxidativePhosphorylation.Phosphorylation.Produces almost 90% of ATPProduces almost 90% of ATP
generated by respiration.generated by respiration.
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Some ATP formed directly duringSome ATP formed directly during
glycolysis and citric acid cycle byglycolysis and citric acid cycle by
substrate-level phosphorylationsubstrate-level phosphorylation.. Enzyme transfers phosphate group fromEnzyme transfers phosphate group from
an organic substrate to ADP, formingan organic substrate to ADP, forming
ATP.ATP.
Enzyme
ADP
P
Substrate
Product
Enzyme
ATP+
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For each molecule of glucoseFor each molecule of glucosedegraded to COdegraded to CO
22& H& H
22O, cell makesO, cell makes
up to 38 ATPup to 38 ATP
Each ATPEach ATP 7.3 kcal/mol of free7.3 kcal/mol of free
energy.energy.
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8.2.1 Glycolysis8.2.1 Glycolysis
Energy investment phase
Glucose
2 ATP used2 ADP + 2 P
4 ADP + 4 P 4 ATP formed
2 NAD+ + 4 e + 4 H+
Energy payoff phase
+ 2 H+2 NADH
2 Pyruvate + 2 H2O
2 Pyruvate + 2 H2O
2 ATP
2 NADH + 2 H+
Glucose
4 ATP formed 2 ATP used
2 NAD+ + 4 e + 4 H+
Net
Glycolysis Citricacidcycle
Oxidative
phosphorylation
ATPATPATP
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Glucose split into two 3C sugars.Glucose split into two 3C sugars.
Sugars oxidized and rearranged to formSugars oxidized and rearranged to formtwo molecules of pyruvate, ionized formtwo molecules of pyruvate, ionized form
of pyruvic acid.of pyruvic acid.
Two phases of glycolysis:Two phases of glycolysis:
1.1. Energy investment phaseEnergy investment phase
Cell invests ATP to provide activationCell invests ATP to provide activation
energy by phosphorylating glucose.energy by phosphorylating glucose.
Requires 2 ATP per glucose.Requires 2 ATP per glucose.
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2.2. Energy payoff phaseEnergy payoff phase
ATP produced by substrate-levelATP produced by substrate-levelphosphorylation.phosphorylation.
NADNAD++ reduced to NADH by electronsreduced to NADH by electrons
released by oxidation of glucose.released by oxidation of glucose.Net yield from glycolysis = 2 ATP and 2Net yield from glycolysis = 2 ATP and 2
NADH per glucose.NADH per glucose.
No CONo CO22 produced during glycolysis.produced during glycolysis.
Glycolysis occurs in presence/absence ofGlycolysis occurs in presence/absence of
OO22..
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Glucose
ATP
ADP
Hexokinase
ATP ATP ATP
Glycolysis Oxidation
phosphorylation
Citricacidcycle
Glucose-6-phosphate
Phosphoglucoisomerase
Phosphofructokinase
Fructose-6-phosphate
ATP
ADP
Fructose-
1, 6-bisphosphate
Aldolase
Isomerase
Dihydroxyacetone
phosphate
Glyceraldehyde-
3-phosphate
The
Glycoly
ticP
athw
ay
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2 NAD+
Triose phosphate
dehydrogenase
+ 2 H+
NADH2
1, 3-Bisphosphoglycerate
2 ADP
2 ATP
Phosphoglycerokinase
Phosphoglyceromutase
2-Phosphoglycerate
3-Phosphoglycerate
2 ADP
2 ATP
Pyruvate kinase
2 H2OEnolase
Phosphoenolpyruvate
Pyruvate
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Overall reaction showingOverall reaction showing allallreactantsreactantsand products resulting fromand products resulting from
glycolysis:glycolysis:
Glucose + 2ATP + 2PGlucose + 2ATP + 2Pii+ 4ADP + 2NAD+ 4ADP + 2NAD++
2 Pyruvate + 2ADP + 4ATP + 2NADH +2 Pyruvate + 2ADP + 4ATP + 2NADH +2H2H++ + 2H+ 2H
22OO
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Equation showingEquation showing netnetreaction ofreaction of
glycolytic pathway.glycolytic pathway.
Glucose + 2PGlucose + 2P ii + 2ADP + 2NAD+ 2ADP + 2NAD++
2 Pyruvate + 2ATP + 2NADH + 2H2 Pyruvate + 2ATP + 2NADH + 2H++ ++
2H2H22OO
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8.2.2 Pyruvate oxidation8.2.2 Pyruvate oxidation
> of original energy in glucose still> of original energy in glucose stillpresent in the 2 molecules of pyruvate.present in the 2 molecules of pyruvate.
If OIf O22is present, pyruvate entersis present, pyruvate enters
mitochondrion where oxidation to COmitochondrion where oxidation to CO22 isiscompleted.completed.
After pyruvate enters mitochondrion viaAfter pyruvate enters mitochondrion via
active transport, it is converted to acetylactive transport, it is converted to acetylcoenzyme A (coenzyme A (acetyl CoAacetyl CoA).).
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Involve multienzyme complex thatInvolve multienzyme complex that
catalyzes three reactions:catalyzes three reactions:
CYTOSOL
Pyruvate
NAD+
MITOCHONDRION
Transport protein
NADH + H+
Coenzyme ACO2Acetyl Co A
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1)1) Carboxyl group removed as COCarboxyl group removed as CO22..
2)2) Remaining 2C fragment oxidized toRemaining 2C fragment oxidized toacetateacetate. An enzyme transfers 2. An enzyme transfers 2
electrons to NADelectrons to NAD++ to form NADH.to form NADH.
3)3) Acetate combines with coenzyme A,Acetate combines with coenzyme A,forming the very reactiveforming the very reactive acetyl CoAacetyl CoA..
Acetyl CoA enters citric acid cycle forAcetyl CoA enters citric acid cycle for
further oxidation.further oxidation.
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Formation of Acetyl CoAFormation of Acetyl CoA
CC CC CC CC CC CC
CoACoACoACoA
CC CC CC CC CC CCPyruvatPyruvat
eses
CoACoACoACoA
CC CC CC CC
NANA
DD++
NANA
DD++
NANADHDH
NANADHDH
CCOO
OOCC
OO
OO
AcetylAcetylCoACoA
CC CC CC CC
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7.2. 3
The
Kre
bs/Citr
ic
7.2. 3
The
Kre
bs/Citr
ic
AcidC
ycle
AcidC
ycle
ATP ATP ATP
Glycolysis Oxidation
phosphorylation
Citricacidcycle
Citricacidcycle
Citrate
Isocitrate
Oxaloacetate
Acetyl CoA
H2O
CO2
NAD+
NADH
+ H+
-Ketoglutarate
CO2NAD+
NADH
+ H+SuccinylCoA
Succinate
GTP GDP
ADP
ATP
FAD
FADH2
P i
Fumarate
H2O
Malate
NAD+
NADH
+ H+
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Acetyl group of acetyl CoAAcetyl group of acetyl CoA
combines withcombines with OAAOAA, forming, formingcitratecitrate..
Citrate regenerated back to OAA.Citrate regenerated back to OAA.3 CO3 CO
22molecules released,molecules released,
including one released duringincluding one released during
conversion of pyruvate to acetylconversion of pyruvate to acetyl
CoA.CoA.
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Cycle generates one ATP per turn byCycle generates one ATP per turn bysubstrate-level phosphorylationsubstrate-level phosphorylation..
GTP is formed by substrate-levelGTP is formed by substrate-level
phosphorylation.phosphorylation.
GTP is used to synthesize an ATPGTP is used to synthesize an ATP
directly.directly.
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Most of chemical energyMost of chemical energy
transferred to NADtransferred to NAD++ and FADand FAD
during redox reactions.during redox reactions.
Reduced coenzymes NADH andReduced coenzymes NADH andFADHFADH
22then transfer high-energythen transfer high-energy
electrons to ETC.electrons to ETC.
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For every acetyl CoA, each cycleFor every acetyl CoA, each cycleproduces:produces:
i.i. 1 ATP by substrate-level1 ATP by substrate-levelphosphorylationphosphorylation
ii.ii.
3 NADH, and3 NADH, and
iii.iii. 1 FADH1 FADH22
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Pyruvate
(from glycolysis,
2 molecules per glucose)
ATP ATP ATP
Glycolysis Oxidation
phosphorylation
CitricacidcycleNAD+
NADH+ H+
CO2
CoA
Acetyl CoA
CoA
CoA
Citric
acid
cycleCO22
3 NAD+
+ 3 H+
NADH3
ATP
ADP + P i
FADH2
FAD
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Summary:Summary:
Acetyl CoA + 3 NADAcetyl CoA + 3 NAD++ + FAD + ADP + P+ FAD + ADP + Pii
+2H+2H22OO
2 CO2 CO22 + CoA-SH + 3NADH + 3H+ CoA-SH + 3NADH + 3H++ ++
FADHFADH22 + ATP+ ATP
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Link
reactions
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8.2.4 Electron transport chain8.2.4 Electron transport chain
(oxidative phosphorylation)(oxidative phosphorylation)4 out of 38 ATP are produced by4 out of 38 ATP are produced by
substrate-level phosphorylation:substrate-level phosphorylation:Glycolysis 2 ATP.Glycolysis 2 ATP.
Citric acid cycle 2 ATP.Citric acid cycle 2 ATP.
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NADH and FADHNADH and FADH22 account for theaccount for the
majority of energy extracted from food.majority of energy extracted from food.
NADH and FADHNADH and FADH22 link glycolysis andlink glycolysis and
citric acid cycle to oxidativecitric acid cycle to oxidativephosphorylation, which uses energyphosphorylation, which uses energy
released by ETC to power ATPreleased by ETC to power ATP
synthesis.synthesis.
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Pathway of Electron TransportPathway of Electron Transport
ETC is a collection of moleculesETC is a collection of molecules
embedded inembedded in cristaecristae..
Most components of ETC areMost components of ETC areproteins bound toproteins bound toprostheticprosthetic
groupsgroups..
Electrons drop in free energy as theyElectrons drop in free energy as theypass down ETC.pass down ETC.
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ATP ATP ATP
GlycolysisOxidative
phosphorylation:
electron transport
and chemiosmosis
Citricacidcycle
NADH
50
FADH2
40 FMN
FeS
I FAD
FeS II
IIIQ
FeS
Cyt b
30
20
Cyt c
Cyt c1
Cyt a
Cyt a3
IV
10
0
Multiproteincomplexes
Freeenergy
(G)re
lativetoO
2(kcal/mol )
H2O
O22 H+ + 1/2
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NADH
(reduced)
NAD
(oxidized)FADH2
(reduced)
FAD(oxidized)
CoQ
(oxidized)
CoQH2(reduced)
Cyto. Oxidase
(oxidized)
Cyto. Oxidase H2
(reduced) O2
H2O
During electron transport along ETC,During electron transport along ETC,
electron carriers alternate between reducedelectron carriers alternate between reduced
and oxidized states as they accept andand oxidized states as they accept anddonate electrons.donate electrons.
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Each component of chain becomesEach component of chain becomes
reduced when it accepts electronsreduced when it accepts electrons
from its uphill neighbor, which isfrom its uphill neighbor, which is
less electronegative.less electronegative.It then returns to its oxidized form asIt then returns to its oxidized form as
it passes electrons to its moreit passes electrons to its more
electronegative downhill neighbor.electronegative downhill neighbor.
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Last cytochrome of chain, cyt aLast cytochrome of chain, cyt a33,,
passes its electrons to oxygen, whichpasses its electrons to oxygen, whichis very electronegative.is very electronegative.
Each oxygen atom also picks up aEach oxygen atom also picks up a
pair of Hpair of H++ from aqueous solution tofrom aqueous solution toform water.form water.
For every two electron carriers (fourFor every two electron carriers (four
electrons), one Oelectrons), one O22molecule ismolecule is
reduced to two molecules of water.reduced to two molecules of water.
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Electrons carried by FADHElectrons carried by FADH22 havehave
lower free energy and are addedlower free energy and are addedat a lower energy level than thoseat a lower energy level than those
carried by NADH.carried by NADH.
ETC provides about one-thirdETC provides about one-third
less energy for ATP synthesisless energy for ATP synthesis
when electron donor is FADHwhen electron donor is FADH22rather than NADH.rather than NADH.
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FADH2NADH
http://en.wikipedia.org/wiki/Image:ETC.PNGhttp://en.wikipedia.org/wiki/Image:ETC.PNGhttp://en.wikipedia.org/wiki/Image:ETC.PNGhttp://en.wikipedia.org/wiki/Image:ETC.PNG -
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ETC generates no ATP directly.ETC generates no ATP directly.Its function is to break the largeIts function is to break the large
free energy drop from food tofree energy drop from food to
oxygen into a series of smalleroxygen into a series of smaller
steps that release energy insteps that release energy in
manageable amounts.manageable amounts.
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Chemiosmosis: Energy-CouplingChemiosmosis: Energy-Coupling
MechanismMechanism
OXIDATIVE PHOSPHORYLATION: ETC &
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1.1. NADH delivers two electrons and twoNADH delivers two electrons and two
protons to the first protein complex (I)protons to the first protein complex (I)
located in cristae.located in cristae.
2.2. Energy is released as the electronsEnergy is released as the electrons
pass down the ETC (electrons movepass down the ETC (electrons move
from high energy to low energy level).from high energy to low energy level).
3.3. Energy is used to actively pump HEnergy is used to actively pump H++
across the membrane..across the membrane..
OXIDATIVE PHOSPHORYLATION: ETC &
CHEMIOSMOSIS : THE MECHANISM
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A MitochondrionA Mitochondrion
MatrixMatrix
AACellCell
One of ItsOne of ItsMitochondriMitochondri
aa
AACristaCrista
OuterOuter
& Inner& InnerMembraneMembraness
ntermembrantermembran
ee
aa bb
cc
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4. Protons move from matrix to4. Protons move from matrix to
intermembrane spaceintermembrane space
5. Protons are moved across by three (of5. Protons are moved across by three (of
the four) complexes/complex I, III and IVthe four) complexes/complex I, III and IV
6. Proton gradient provide energy for ATP6. Proton gradient provide energy for ATP
synthesis.synthesis.
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7.7. Diffusion of protons from intermembraneDiffusion of protons from intermembrane
space to the matrix of mitochondrionspace to the matrix of mitochondrion
through ATP synthase (Hthrough ATP synthase (H++ onlyonly
permeable to ATP synthase)permeable to ATP synthase)
8.8. As protons pass through it, energy isAs protons pass through it, energy is
obtained to phosphorylate ADP into ATPobtained to phosphorylate ADP into ATP
ADP + PADP + P ii ATP.ATP.
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10. FADH10. FADH2 delivers its electron via proteindelivers its electron via protein
complex II (at lower energy level).complex II (at lower energy level).
1 FADH1 FADH22PRODUCES 2 ATPPRODUCES 2 ATP
1 NADH PRODUCES 3 ATP1 NADH PRODUCES 3 ATP
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3.3. Process is done two more timeProcess is done two more time
times. Electrons are passed throughtimes. Electrons are passed throughprotein complexes III & IV, whichprotein complexes III & IV, which
transport two more Htransport two more H++ acrossacross
membrane.membrane.4.4. After passing through three proteinAfter passing through three protein
complexes, electrons combine withcomplexes, electrons combine with
one oxygen atom and two Hone oxygen atom and two H++ to formto formwater.water.
MitochondrialMitochondrial
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MitochondrialMitochondrial(1)(1)
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6.6. Cristae membrane impermeable toCristae membrane impermeable to
HH++ except through ATP synthase. Asexcept through ATP synthase. Asprotons pass through it, energy isprotons pass through it, energy is
obtained to make ATP from ADP &obtained to make ATP from ADP &
PPi..
7.7. FADHFADH2 delivers its electron viadelivers its electron via
protein complex II so, fewerprotein complex II so, fewerelectrons are passed into inter-electrons are passed into inter-
membrane space.membrane space.
8 2 5 C l l ti f T t l ATP P d ti8 2 5 C l l ti f T t l ATP P d ti
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8.2.5 Calculations of Total ATP Production8.2.5 Calculations of Total ATP Production
by Cellular Respirationby Cellular Respiration
CYTOSOL Electron shuttlesspan membrane 2 NADH
or
2 FADH2
MITOCHONDRION
Oxidative
phosphorylation:electron transportand
chemiosmosis
2 FADH22 NADH 6 NADH
Citric
acid
cycle
2
Acetyl
CoA
2 NADH
Glycolysis
Glucose2
Pyruvate
+ 2 ATP
by substrate-level
phosphorylation
+ 2 ATP
by substrate-level
phosphorylation
+ about 32 or 34 ATP
by oxidation phosphorylation, depending
on which shuttle transports electronsform NADH in cytosol
About36 or 38 ATPMaximum per glucose:
Summary ofSummary ofGl M t b liGl M t b li
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mm y fmm y fGlucose MetabolismGlucose Metabolism
(2)(2)
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Products generated when a molecule ofProducts generated when a molecule of
glucose is oxidized to 6 COglucose is oxidized to 6 CO
22 molecules:molecules:
ConversionsConversions
NADH in cytoplasm produces 2 or 3 ATPNADH in cytoplasm produces 2 or 3 ATP
by oxidative phosphorylation dependingby oxidative phosphorylation dependingon shuttle system used to transporton shuttle system used to transport
electrons from cytosol into mitochondrion:electrons from cytosol into mitochondrion:
If electrons are passed toIf electrons are passed to FADFAD, e.g., e.g.brain cells -brain cells - 2 ATP2 ATP..
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If electrons are passed toIf electrons are passed to NADNAD++,,e.g., liver cells & heart cells =e.g., liver cells & heart cells = 3ATP3ATP
In mitochondria:In mitochondria:
NADH - 3 ATPNADH - 3 ATP
FADHFADH22 2ATP 2ATP
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NADH(glycolysis)
Malate-
aspartate
NAD
NADHETC
NADH(glycolysis)
GP
FAD
FADH2ETC
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Krebs CycleKrebs Cycle
6 NADH = 6 x 3 ATP = 18 ATP6 NADH = 6 x 3 ATP = 18 ATP2 FADH2 = 2 x 2 ATP = 4 ATP2 FADH2 = 2 x 2 ATP = 4 ATP
Substrate-level phosphorylation = 2Substrate-level phosphorylation = 2
ATPATP
Total YieldTotal Yield
Glycolysis = 2 ATPGlycolysis = 2 ATPAerobic respiration = 34 or 36 ATPAerobic respiration = 34 or 36 ATP
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5.5. SummarySummary
PathwayPathway Substrate-levelSubstrate-levelphosphorylatiophosphorylationn
OxidativeOxidativephosphorylationphosphorylation
TotalTotalATPATP
GlycolysisGlycolysis 2 ATP2 ATP 2 NADH = 4 - 62 NADH = 4 - 6
ATPATP
6 - 86 - 8
Acetyl CoAAcetyl CoA 2 NADH = 6 ATP2 NADH = 6 ATP 66
Krebs cycleKrebs cycle 2 ATP2 ATP 6 NADH = 18 ATP6 NADH = 18 ATP
2 FADH2 = 4 ATP2 FADH2 = 4 ATP
2424
TotalTotal 4 ATP4 ATP 32 34 ATP32 34 ATP 36-3836-38
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Energy Harvested from GlucoseEnergy Harvested from Glucose
ytoplasm)ytoplasm) GlucoseGlucose
2 NADH2 NADH
2 NADH2 NADH6 NADH6 NADH2 FADH2 FADH22
2 Pyruvates2 Pyruvates
2 CO2 CO22
4 CO4 CO22
22ATPATP
44ATPATP
itochondrialitochondrialMatrix)Matrix)
(Inner(Innerembrane)embrane)
22ATPATP
3232ATPATP
ElectronElectronTransportTransportSystemSystem
GlycolysiGlycolysiss
KrebsKrebsCycleCycle
WaterWater
OxygenOxygen
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Efficiency of respirationEfficiency of respiration
Complete oxidation of glucose =Complete oxidation of glucose = 686686
kcal/mol.kcal/mol.
Phosphorylation of ADP to form ATP =Phosphorylation of ADP to form ATP = 7.37.3
kcal/mol.kcal/mol.
Efficiency of respirationEfficiency of respiration
== 7.3 kcal/mol x 38 ATP/glucose x 100%7.3 kcal/mol x 38 ATP/glucose x 100%
686 kcal/mol glucose686 kcal/mol glucose
= 40%.= 40%.
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60% energy from glucose lost60% energy from glucose lost
as heat.as heat.Some used to maintain bodySome used to maintain bodytemperature (37C).temperature (37C).
Efficient in energy conversion.Efficient in energy conversion.
8 3 A bi i ti8 3 A bi i ti
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8.3 Anaerobic respiration8.3 Anaerobic respiration
Qxidative phosphorylation ceasesQxidative phosphorylation ceasesin absence of Oin absence of O
22..
Some cells oxidize organic fuelSome cells oxidize organic fuel
and generate ATP without use ofand generate ATP without use of
OO22through fermentation.through fermentation.
E.g., anaerobic catabolism ofE.g., anaerobic catabolism ofsugars.sugars.
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Fermentation generate ATP fromFermentation generate ATP fromglucose by substrate-levelglucose by substrate-level
phosphorylation as long as there isphosphorylation as long as there is
NADNAD++
to accept electrons.to accept electrons.If NADIf NAD++ pool is exhausted,pool is exhausted,
glycolysis shuts down.glycolysis shuts down.
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Under aerobic conditions, NADHUnder aerobic conditions, NADH
transfers electrons to ETC, andtransfers electrons to ETC, andrecycles NADrecycles NAD++..
Anaerobic - ATP generated byAnaerobic - ATP generated byglycolysis; NADglycolysis; NAD++ recycled byrecycled by
transferring electrons from NADHtransferring electrons from NADH
to pyruvate/derivatives of pyruvate.to pyruvate/derivatives of pyruvate.
8.3.1 Ethanol Fermentation8.3.1 Ethanol Fermentation
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8.3.1 Ethanol Fermentation
CO2+ 2 H+
2 NADH2 NAD+
2 Acetaldehyde
2 ATP2 ADP + 2 Pi
2 Pyruvate
2
2 Ethanol
Alcohol (ethanol) fermentation
Glucose Glycolysis
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Two steps:Two steps:
1.1. Pyruvate converted toPyruvate converted to
acetaldehyde (2C), by removal ofacetaldehyde (2C), by removal of
COCO22..
2.2. Acetaldehyde reduced by NADHAcetaldehyde reduced by NADH
to ethanol.to ethanol.
Alcohol fermentation by yeast -Alcohol fermentation by yeast -brewing and winemaking.brewing and winemaking.
8 3 2 Lactic Fermentation8 3 2 Lactic Fermentation
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8.3.2 Lactic Fermentation8.3.2 Lactic Fermentation
+ 2 H+2 NADH2 NAD+
2 ATP2 ADP + 2 P i
2 Pyruvate
2 Lactate
Lactic acid fermentation
Glucose Glycolysis
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Pyruvate reduced by NADH to lactatePyruvate reduced by NADH to lactate
without release of COwithout release of CO22..Lactic acid fermentation by fungi andLactic acid fermentation by fungi and
bacteria - cheese and yogurt.bacteria - cheese and yogurt.
Human muscle cells switch from aerobicHuman muscle cells switch from aerobicrespiration to lactic acid fermentation torespiration to lactic acid fermentation to
generate ATP when Ogenerate ATP when O22 is scarce.is scarce.
Waste product, lactate, causes muscleWaste product, lactate, causes musclefatigue - converted back to pyruvate infatigue - converted back to pyruvate in
liver.liver.
GLUCOSE (6C)
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GLUCOSE (6C)
2PYRUVATES (3C)
2LACTATE (3C)
2NAD+
2NADH
+ 2H+
2NAD+
2NADH
+ 2H+
CO2
2ETHANAL /
ASETALDEHYDE (2C)
2ETHANOL (2C)
2Pyruvates converted into
2ethanol (2C) &2CO2
2NADH are used
2 ATP are produced
Yeast cell
2Pyruvates converted into
2lactate (3C)2NADH are used
2 ATP are produced
muscle cell/bacteria 2ATP
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Fermentation and Cellular RespirationFermentation and Cellular Respiration
ComparedCompared
SimilaritiesSimilarities both use both use
1.1. GlycolysisGlycolysis : oxidize sugars to pyruvate: oxidize sugars to pyruvate- 2 ATP produced by substrate-level- 2 ATP produced by substrate-level
phosphorylation.phosphorylation.
2.2. NADNAD++
: oxidizing agent - accept: oxidizing agent - acceptelectrons from food during glycolysis.electrons from food during glycolysis.
DiffDiff
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DifferenceDifference
1.1. Mechanism for oxidizing NADH to NADMechanism for oxidizing NADH to NAD++..
Fermentation - electrons of NADHFermentation - electrons of NADHpassed to anpassed to an organic moleculeorganic molecule toto
regenerate NADregenerate NAD++..
Respiration - electrons of NADH passedRespiration - electrons of NADH passedtoto OO
22, generating ATP by oxidative, generating ATP by oxidative
phosphorylation.phosphorylation.
2.2. ATP generated per molecule of glucose.ATP generated per molecule of glucose. Aerobic :Aerobic : 36 - 3836 - 38 ATP.ATP.
Anaerobic :Anaerobic : 22 ATP.ATP.
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Facultative AnaerobesFacultative Anaerobes
Makes ATP aerobically if OMakes ATP aerobically if O22isis
present; switch to fermentation inpresent; switch to fermentation inabsence of Oabsence of O
22..
E.g., yeast, many bacteria & humanE.g., yeast, many bacteria & human
muscle cells (cellular level).muscle cells (cellular level).
Glucose
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Pyruvate
CYTOSOL
No O2 present
Fermentation
Ethanol
or
lactate
Acetyl CoA
MITOCHONDRION
O2 present
Cellular respiration
Citric
acidcycle
8.4 Metabolism of Fat and Protein8.4 Metabolism of Fat and Protein
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Citricacidcycle
Oxidativephosphorylation
Proteins
NH3
Aminoacids
Sugars
Carbohydrates
Glycolysis
Glucose
Glyceraldehyde-3-P
Pyruvate
Acetyl CoA
Fatty
acids
Glycerol
Fats
CatabolismCatabolism
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CatabolismCatabolism
Carbohydrates:Carbohydrates:PolysaccharidesPolysaccharides
(starch/glycogen) hydrolyzed to(starch/glycogen) hydrolyzed to
glucose monomers that enterglucose monomers that enterglycolysis.glycolysis.
Hexose sugars (galactose andHexose sugars (galactose and
fructose) - modified to undergofructose) - modified to undergo
glycolysis.glycolysis.
Protein:Protein:
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Protein:Protein:
Proteins digested to individual aminoProteins digested to individual amino
acids.acids.
Amino groups removed viaAmino groups removed via
deaminationdeamination..
Nitrogenous waste excreted asNitrogenous waste excreted as
ammonia, urea, or another wasteammonia, urea, or another waste
product.product.
Carbon skeletons modified by enzymesCarbon skeletons modified by enzymes
and enter as intermediaries intoand enter as intermediaries into
glycolysis or citric acid cycle.glycolysis or citric acid cycle.
Fats:Fats:
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Fats:Fats:
Fats digested to glycerol and fattyFats digested to glycerol and fatty
acids.acids.
Glycerol converted to G3P Glycerol converted to G3P
enters glycolysis.enters glycolysis.Fatty acids split into 2C fragmentsFatty acids split into 2C fragments
viavia beta oxidationbeta oxidation..
Enter citric acid cycle as acetylEnter citric acid cycle as acetylCoA.CoA.
Bi th i (A b li P th )Bi th i (A b li P th )
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Biosynthesis (Anabolic Pathways)Biosynthesis (Anabolic Pathways)
Intermediaries in glycolysis and citric acidIntermediaries in glycolysis and citric acid
cycle can be diverted to anaboliccycle can be diverted to anabolic
pathways.pathways.
E.g., human cell synthesizes 10 differentE.g., human cell synthesizes 10 different
amino acids by modifying compoundsamino acids by modifying compounds
from citric acid cycle.from citric acid cycle.
Glucose synthesized from pyruvate.Glucose synthesized from pyruvate.
Fatty acids from acetyl CoA.Fatty acids from acetyl CoA.
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Glycolysis and citric acid cycleGlycolysis and citric acid cycle
function as metabolic interchangesfunction as metabolic interchangesthat enable cells to convert one kindthat enable cells to convert one kind
of molecule to another.of molecule to another.
E.g., conversion of excess proteinsE.g., conversion of excess proteins
and carbohydrates to fats throughand carbohydrates to fats through
intermediaries of glycolysis and citricintermediaries of glycolysis and citricacid cycle.acid cycle.