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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