The Flow of Energy in a Cell Potential Energy Kinetic Energy
Transcript of The Flow of Energy in a Cell Potential Energy Kinetic Energy
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BCOR 011 Lecture 11 BCOR 011 Lecture 11 Chapter 8Chapter 8
The Flow of Energy in a CellThe Flow of Energy in a Cell
Sept 26, 2005Sept 26, 2005
Figure 8.12
Potential Energy Kinetic Energy-stored in height-stored in battery (conc/charge)-stored in BONDS
-energy of movement-molecules colliding, vibrating-HEAT, light
Energy: the capacity to effect Energy: the capacity to effect change change Two types of energyTwo types of energy
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Potential Energy Stored in: Potential Energy Stored in:
On the platform, a diverhas more potential energy.
Diving converts potentialenergy to kinetic energy.
Climbing up converts kineticenergy of muscle movement to potential energy.
In the water, a diver hasless potential energy.
Figure 8.2 Figure 8.5locationlocation
gradientgradient
ChemicalChemicalbondsbonds
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1st Law of Thermodynamics1st Law of ThermodynamicsEnergy is neither created nor destroyed in
chemical reactionsbut only Transformed from one form to another
Potential Potential
Kinetic Kinetic
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Atoms bonded inAtoms bonded inHigh Potential EnergyHigh Potential EnergyConfigurationConfiguration
Atoms bonded inAtoms bonded inLow Potential EnergyLow Potential EnergyConfigurationConfiguration
Energy is ReleasedEnergy is Released
In a chemical reactionproducts have a lower potential energy than reactants
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a Chemical Reaction
Reorganization of Bonds of existing molecules- an exchange
Example
H-C-H
--
H
H
O=O
O=O
O=C=O
OH H
OH H
Same # of H’sSame # of C’sSame # of O’s
All Start with filled outer shell of electronsAll End with outer shell of electrons
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High Energy
Low Energy
H-C-H
--
H
H
O=O
O=C=O OH H
ENERGYENERGYRELEASEDRELEASED
reducedreduced
oxidizedoxidized8
Energy that is released:Energy that is released:
Has the capacity to Has the capacity to DO WORKDO WORK
Raise potential state of something elseRaise potential state of something else
Or effect movement Or effect movement –– heat, motionheat, motion
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Types of Work:Types of Work:
1 Biosynthetic: 1 Biosynthetic: changes in chemical bondschanges in chemical bonds
reactantsreactants productsproductsA + BA + B C + DC + D
A+BA+B
C+DC+DE+FE+F
G+HG+H
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Other Types of WorkOther Types of Work
2. Chemical Concentration Gradient2. Chemical Concentration Gradient
AAinsideinside + + BBoutsideoutside AAoutsideoutside + + BBinsideinside
eveneven eveneven lowlow highhigh
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3. Electrical work 3. Electrical work –– movement of ions acrossmovement of ions acrossa membrane against an electrochemical gradienta membrane against an electrochemical gradient
AAinsideinside + + BBoutsideoutside AAoutsideoutside + + BBinsideinside
eveneven eveneven ++ --12
Other Types of WorkOther Types of Work
Mechanical Work: Movement, MotilityMechanical Work: Movement, Motility44
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Conformation Conformation ConformationConformationAA BB
PoisedPoisedHigh EnergyHigh Energy
RelaxedRelaxedLow EnergyLow Energy
Another form ofAnother form ofMOVEMENTMOVEMENT
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• Some organisms – Convert energy to light, as in bioluminescence
Figure 8.1
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Energy that is released:Energy that is released:
Has the capacity to Has the capacity to DO WORKDO WORK
Raise potential state of something elseRaise potential state of something else
Or effect movement Or effect movement –– heat, motionheat, motion
But some is always lost to disorderBut some is always lost to disorder16
ChangeChangeIn potentialIn potentialEnergyEnergy
Released EnergyReleased Energy
State 1State 1
State 2State 2
AbilityAbilityTo doTo doworkwork
++ RandomnessRandomness
Gross PayGross PayTake Take HomeHomePayPay
++ TaxesTaxes
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Kinetic Energy can be dissipated: Randomized
Kinetic EnergySoundFloor Vibration
Chance of going in REVERSE?
Releases Energy
RequiresEnergy Input
Disorder
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Only time this is not trueOnly time this is not trueis when no movement anymoreis when no movement anymore
ieie. at . at abosoluteabosolute zerozero
Second law of Thermodynamics:Second law of Thermodynamics:
The Universe is proceeding to a The Universe is proceeding to a State of MAXIMUM DISORDERState of MAXIMUM DISORDER
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00oo KK -- no motion, no “taxes”no motion, no “taxes”
A Progressive Scale:A Progressive Scale:Higher the temperature,Higher the temperature,
the more that disorder comes into playthe more that disorder comes into playhigher proportion of energy lost to randomnesshigher proportion of energy lost to randomness
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EnthalpyEnthalpyFree Free EnergyEnergy ++ EntropyEntropy
ChangeChangeIn potentialIn potentialEnergyEnergy
Released EnergyReleased Energy
State 1State 1
State 2State 2
AbilityAbilityTo doTo doworkwork
++ RandomnessRandomness
∆∆HH ∆∆GG ∆∆SSTT
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RandomnessRandomness
FreedomFreedom of of Movement Movement
or or PositionPosition
ENTROPYENTROPY∆∆SS
((disorder)disorder)
ENTHALPYENTHALPY∆∆HH
Change in Change in Chemical Bond Chemical Bond
Energy Energy
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ENTHALPYENTHALPY∆∆HH
Change in Change in Chemical Bond Chemical Bond
Energy Energy
GlucoseGlucose++
6 O6 O22
6 CO6 CO22++
6 H6 H22OO
6 Glucose6 Glucose++
6 O6 O22
6 CO6 CO22++
6 H6 H22OO
TimeTime
--∆∆HHHighHigh
PotentialPotentialLow PotentialLow Potential
HighHighPotentialPotential
Low PotentialLow Potential
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ENTROPYENTROPY∆∆SS
Change in Change in Freedom Freedom
Number ofNumber ofpossible statespossible statesthat can be that can be present in:present in:
Roll of “2”Roll of “2”Only 1 possible Only 1 possible
“state” “state”
Roll of “7”Roll of “7”
6 possible 6 possible “states”“states”
Low entropyLow entropy
High entropyHigh entropy24
NaClNaClcrystalcrystal
NaNa++ ClCl--ions in waterions in water
NaClNaClcrystalcrystal
NaNa++ ClCl--ions in waterions in water
timetime
ENTROPYENTROPY∆∆SS
Change in Change in Freedom Freedom
Number ofNumber ofPossible StatesPossible StatesThat can be That can be Present inPresent in
++∆∆SS
FewFewStatesStates
ManyManyStatesStates
“Dispersed”“Dispersed” FewFewStatesStates
ManyManyStatesStates
“Dispersed”“Dispersed”
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The The Free EnergyFree Energy Change Change ∆∆GG
Dictates whether a reaction will Dictates whether a reaction will Proceed Proceed spontaneouslyspontaneously or notor not
Whether a Reaction isWhether a Reaction isFavorableFavorable or or Unfavorable Unfavorable
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∆∆H H = = TT∆∆S S ++ ∆∆G G
Change inChange inChemicalChemicalBond Bond EnergyEnergy
Energy thatEnergy thatGoes to Goes to
Do Useful Work Do Useful Work
Energy thatEnergy thatGoes to Goes to
RandomnessRandomness
EnthalpyEnthalpy ““free energy” free energy” (Gibb’s Free Energy)(Gibb’s Free Energy)
EntropyEntropyDependentDependent
On On TemperatureTemperatureKinetic MovementKinetic Movement
∆∆G G = = ∆∆H H -- TT∆∆SSIf If ∆∆G = negative # G = negative # reaction is energetically favorable reaction is energetically favorable
““spontaneous”spontaneous”
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∆∆GG = = ∆∆HH –– TT∆∆SS-- ∆∆G is G is favorablefavorable exergonicexergonic “spontaneous”“spontaneous”++ ∆∆G is G is NOT favorable,NOT favorable, endergonicendergonic, , nonspontaneousnonspontaneous 28
An exergonic reaction– Proceeds with a net release of free energy and is spontaneous
Figure 8.6
Reactants
Products
Energy
Progress of the reaction
Amount ofenergyreleased (∆G <0)
Free
ene
rgy
(a) Exergonic reaction: free energy released
““will happen”will happen”
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An An endergonicendergonic reactionreaction–– Is one that Is one that absorbs free energyabsorbs free energy from its from its
surroundings and is surroundings and is nonspontaneousnonspontaneous
Figure 8.6
Energy
Products
Amount ofenergyreleased (∆G>0)
Reactants
Progress of the reaction
Free
ene
rgy
(b) Endergonic reaction: energy required
““doesn’t happen”doesn’t happen”
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2 Factors Contribute to Whether a Reaction will Occur:
change in Bond Energy change in EntropyReduced
Oxidized
Complex
Simple
Net Useful Energy (Net Useful Energy (∆∆G)G)The sum of these is the
If net ENERGY RELEASED - EXERGONIC = FAVORABLE
If require net ENERGY INPUT - ENDERGONIC = UNFAVORABLE
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Complex Simple
Reduced (no oxygens)
Oxidized
High
Lowest
H-C-C-C-C-C-C-C-C-HH
H H
H HHH
HH H H
H
H
H H
H H-C-HH
H
O=C=O
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R-C-OHH
H
Lower
R-C-H
=O
R-C-OH=O
hydrocarbon
alcohol
aldehyde
acidchan
ge in
Bon
d En
ergy
change in Entropy
Low
fats
sugars
Finalproduct
Carbon dioxide 32
EXERGONIC REACTIONSgasoline burnsiron rustshydrogen and oxygen form water (explosive!)
Either: go to bonding arrangement with lower potential energy
Or: go from a more complex state to a simpler state
1 molecule of 8 carbons vs 8 molecules of 1 carbon
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∆∆H=H=∆∆S=S=∆∆G=G=
--++
veryvery --
SpontaneousSpontaneousFavorableFavorable -- it it cancan happen happen
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favorablefavorablefavorablefavorablefavorablefavorable
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∆∆H = H = HHproductsproducts --HHreactantsreactants
−− ∆∆HHexothermicexothermicHeat releasedHeat released
+ ∆+ ∆HHendoendothermicthermicHeat inputHeat input
icepackicepack
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∆∆H=H=∆∆S=S=∆∆G=G=
++++--
Unfavorable Unfavorable Very favorableVery favorable
favorablefavorable
SpontaneousSpontaneousFavorableFavorable -- it it cancan happenhappenEntropy overwhelms EnthalpyEntropy overwhelms Enthalpy
Entropy Driven ReactionEntropy Driven Reaction
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∆∆H=H=∆∆S=S=∆∆G=G=
------
very favorable very favorable unfavorableunfavorablefavorablefavorable
SpontaneousSpontaneousFavorableFavorable -- it it cancan happenhappenEnthalpy overweighs Entropy Enthalpy overweighs Entropy
Enthalpy Driven ReactionEnthalpy Driven Reaction
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∆∆GG = = ∆∆HH –– TT∆∆SS-- ((--)) -- (+)(+)
∆∆GG = = ∆∆HH –– TT∆∆SS-- ((--)) -- ((--))
∆∆GG = = ∆∆HH –– TT∆∆SS-- (+)(+) -- (+)(+)
EnthalpicallyEnthalpicallyDriven Driven RxnRxn
EntropicallyEntropicallyDriven Driven RxnRxn
SpontaneousSpontaneousFavorable Favorable RxnRxn 38
∆∆H=H=∆∆S=S=∆∆G=G=
++--++
unfavorable unfavorable unfavorableunfavorableunfavorableunfavorable
NonNon--spontaneousspontaneousNOT Favorable NOT Favorable -- it can it can NOTNOT happen happen
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A typical ENDERGONIC/Unfavorable/NonSpontaneous REACTION
- building a polymer
Monomer + Monomer Polymer + Water
Requires 5.5 energy units
How could we make it occur?
WILL NOT OCCUR
Integratean exergonic reaction with an endergonic reaction
If have a captured packet of energy of 7.3 energy units
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Drive otherwiseotherwise unfavorablereactions
COUPLED ReactionsCOUPLED Reactions Tie a favorable Tie a favorable rxnrxn withwithAn otherwise unfavorable An otherwise unfavorable rxnrxn
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∆G = +5.5 kcal/mole
1.1.
ATP
ADP + Pi
∆G = -7.3 kcal/mole
2. ATP+ H2. ATP+ H22O ADP + PiO ADP + Pi
Favorable or unfavorable ?Favorable or unfavorable ? 42
∆G = -7.3 kcal/mole+∆G = +5.5 kcal/mole
∆G = -1.8 kcal/moleNet Net rxnrxn
Note:Note:Each step is Each step is
favorablefavorable
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Coupled Reaction
ADP -P + monomer1 ADP-monomer1 + PI’m free!∆G = -1.0
Net: ATP +H2O ADP + Pmonomer1 + monomer2 monomer1-monomer2 + H2O
7.3 units released
5.5 units needed
ADP-monomer1 + monomer 2
ADP + monomer1-monomer 2Now I’m free too!
∆G = -0.8
Now tied together
(ATP)
DO NOT LET ATP FALL APART IN 1 STEP, use energy in its bond to MAKE the polymer linkage
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Another Example of a Coupled Reaction
Endergonic reaction: ∆G is positive, reaction is not spontaneous
∆G = +3.4 kcal/molGlu Glu
∆G = + 7.3 kcal/molATP H2O+
+ NH3
ADP +
NH2
Glutamicacid
Ammonia Glutamine
Exergonic reaction: ∆ G is negative, reaction is spontaneous
P
Coupled reactions: Overall ∆G is negative;together, reactions are spontaneous ∆G = –3.9 kcal/molFigure 8.10
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Three types of cellular work powered by Three types of cellular work powered by ATP hydrolysisATP hydrolysis
(c) Chemical work: ATP phosphorylates key reactants
P
Membraneprotein
Motor protein
P i
Protein moved(a) Mechanical work: ATP phosphorylates motor proteins
ATP
(b) Transport work: ATP phosphorylates transport proteins
Solute
P P i
transportedSolute
GluGlu
NH3
NH2
P i
P i
+ +
Reactants: Glutamic acid and ammonia
Product (glutamine)made
ADP+
P
Figure 8.11
BiosyntheticBiosyntheticCoupledCoupled
RxnRxn
DrivingDrivingConformationalConformational
ChangesChangesOf Of
ProteinsProteins
PhysicalPhysicalmovementmovement
ActiveActiveTransportTransport
PumpsPumps
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EquilibriumReactions in a closed system
– Eventually reach equilibrium
Figure 8.7 A
(a) A closed hydroelectric system. Water flowing downhill turns a turbine that drives a generator providing electricity to a light bulb, but only until the system reaches equilibrium.
∆G < 0 ∆G = 0
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In living systems– Experience a constant flow of materials in – Constant Energy Input
Figure 8.7
(b) An open hydroelectric system. Flowing water
keeps driving the generator because intake and outflow of water keep the system
from reaching equlibrium.
∆G < 0
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cellular respiration is a series of favorable reactions
Figure 8.7 (c) A multistep open hydroelectric system. Cellular respiration is
analogous to this system: Glucoce is brocken down in a seriesof exergonic reactions that power the work of the cell. The productof each reaction becomes the reactant for the next, so no reaction reaches equilibrium.
∆G < 0
∆G < 0
∆G < 0
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For example, oxidation of glucose:C6H12O6 (glucose) + 6O2 6CO2 + 6H2O
∆G= -686 kcal/mol ∆H = -673 kcal/mol
T∆S= -13 kcal/mol
in the cell, this is done in >21 steps!
Capture the energy in small packetsCapture the energy in small packetsieie, 36 ATP units of 7.3 kcal, 36 ATP units of 7.3 kcal
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Summary:Summary:--matter is neither created nor destroyedmatter is neither created nor destroyed--the universe is proceeding toward disorderthe universe is proceeding toward disorder
∆∆HH = enthalpy (heat content,bond energy)= enthalpy (heat content,bond energy)∆∆SS = entropy (randomness)= entropy (randomness)
∆∆GG = free energy (available to do work)= free energy (available to do work)
∆∆GG = = ∆∆HH -- TT∆∆SS
-- coupled reactionscoupled reactions
--biological systems always need biological systems always need constant energy inputconstant energy input