““Bioenergetics”Bioenergetics”

Prof. Dr. Prof. Dr. Metin TULGARMetin TULGAR

Energy Concept In Living CreatureEnergy Concept In Living Creaturess

EnergyEnergy is the is the ability of an object to do ability of an object to do workwork..

Some examples:Some examples:

Transmittion of water from roots toTransmittion of water from roots to the leaves, the leaves, AAny movement of ny movement of anan animal, animal, PumpPump of blood to the vesselsof blood to the vessels..

Energy source of livings: Energy source of livings: NutrientsNutrients..

Kinds ofKinds of Energ Energies for Livingsies for Livings

A A mechanical workmechanical work:: in muscle contraction, in muscle contraction,

An An electrical workelectrical work: : ionsions, , crossing across thecrossing across the membrane,membrane,

A A chemical workchemical work:: during the synthesis of a substance during the synthesis of a substance..

If livings can’t transform energy to other forms, If livings can’t transform energy to other forms,

they canthey can not not survive.survive.

TTypical events proving that the cells use energyypical events proving that the cells use energy::

Cells keep substances in high concentration.Cells keep substances in high concentration.

That the cells move.That the cells move.

Ability tAbility to synthesize macromolecules from o synthesize macromolecules from micromolecules.micromolecules.

BBioenergeticsioenergetics is; is;

TThe he sciencescience that deals with how that deals with how the the energyenergy is is

producedproduced and and transformedtransformed in living creatures.in living creatures.

BIOTHERMODYNAMICSBIOTHERMODYNAMICS

BioBio(living) +(living) +thermothermo(heat) + (heat) + dynamicsdynamics(power):(power):

BiothermodynamicsBiothermodynamics is the science that deals with is the science that deals with

tthehe energyenergy and its and its transformationstransformations in in livingslivings..

Here are some Here are some concepts of thermodynamicsconcepts of thermodynamics::

WW: Work that the : Work that the SystemSystem does. does.

QQ: : Energy amount of the Energy amount of the SystemSystem

EE:: Internal Energy of the Internal Energy of the SystemSystem

Thermodynamics deal with the relationships of theseThermodynamics deal with the relationships of these

concepts.concepts.

An example An example SystemSystem: : Amip Amip (Single-celled organism)(Single-celled organism)..

Amip consumes energy when it moves.Amip consumes energy when it moves. Heat is transfered between the invironment and Amip.Heat is transfered between the invironment and Amip. Internal energy source of Amip is food.Internal energy source of Amip is food.

Laws of ThermodynamicsLaws of Thermodynamics

In order to In order to determine the lastdetermine the last situation of thissituation of this

SystemSystem..

Physical charasteristics of a Physical charasteristics of a SystemSystem:: MMassass,, VolumeVolume,, AAnd nd TTemperatureemperature..

There are three laws There are three laws of of thermodynamics:thermodynamics:

1.1. ZerothZeroth law of thermodynamics law of thermodynamics

2.2. FirstFirst law of thermodynamics law of thermodynamics

3. 3. SecondSecond law of thermodynamics law of thermodynamics

Zeroth Law of ThermodynamicsZeroth Law of Thermodynamics

The The zeroth law of thermodynamicszeroth law of thermodynamics state that state that::

““IIf two badies are in thermal equilibrium with a thirdf two badies are in thermal equilibrium with a third

body, they are also in thermal equilibrium with eachbody, they are also in thermal equilibrium with each

other.other.””

Figure #1: Figure #1: Three Three bodies in thermalbodies in thermalequilibrium.equilibrium.

Consider three bodies A, B, and C Consider three bodies A, B, and C with absolute temperatures Twith absolute temperatures TAA, T, TBB, ,

and Tand TC C in thermal equilibrium.in thermal equilibrium.

According to the zeroth law of According to the zeroth law of thermodynamicsthermodynamics;;

if Tif TAA= T= TBB, and T, and TA A == TTCC ;;

then Tthen TB B == TTC C ..

B

TB

C

TCA

TA

Also known asAlso known as conservation of energy principle.conservation of energy principle.

energy changeenergy change of of ((heatheat++workwork)) == internal energy internal energy changechange..

Internal EnergyInternal Energy: Total energy of all the microscobic forms of : Total energy of all the microscobic forms of energy.energy. ( atoms,molecules,ions )( atoms,molecules,ions )

First Law of ThermodynamicsFirst Law of Thermodynamics

Scientific definitionScientific definition of First Law of First Law::

ΔEi = Q ΔEi = Q ++ W W . .

ΔEiΔEi::internal energyinternal energy changechange, , QQ::heatheat, , WW::wrok .wrok .

Internal Energy Function:Internal Energy Function: Ei = u( V, T )Ei = u( V, T ) . .

V: V: volume , T: absolute temperature .volume , T: absolute temperature .

Differentiation of Internal Energy Function:Differentiation of Internal Energy Function:

dEi = (dEi = (u/u/T)T)VVdT+(dT+(u/u/V)V)TTdVdV

Consider Consider conservation of energy principle;conservation of energy principle; Eu = Ei + EoEu = Ei + Eo

Eu: Eu: energy of the universe,energy of the universe, Ei: Ei: internal energy of system,internal energy of system, Eo: Eo: energy of environment.energy of environment.

If “energy can be neither created nor destroyed”, If “energy can be neither created nor destroyed”,

then Eu is constant.then Eu is constant. Change in internal energy of the system: Ei to Ei’Change in internal energy of the system: Ei to Ei’ Change in energy of environment: Eo to Eo’Change in energy of environment: Eo to Eo’ Ei + Eo = Ei’ + Eo’Ei + Eo = Ei’ + Eo’ Ei – Ei’ = Eo’ – EoEi – Ei’ = Eo’ – Eo Then, ΔEi = ΔEoThen, ΔEi = ΔEo

First Law could be concluded as this:First Law could be concluded as this:

““Energy can be neither created nor destroyed,Energy can be neither created nor destroyed,

it can only change forms”it can only change forms”

Ideal Gas Equation of StateIdeal Gas Equation of State

Ideal gas is an imaginary gas which hasIdeal gas is an imaginary gas which has

no volume,no volume,

no attractive and repulsive forces between its no attractive and repulsive forces between its molecules, andmolecules, and

no loss of kinetic energy when its molecules collided no loss of kinetic energy when its molecules collided with each other. with each other.

Ideal gas equation of state: P.V = n.R.TIdeal gas equation of state: P.V = n.R.T

P: P: pressure,pressure, V: V: volume,volume, n:n: # of moles, # of moles, R: R: gas constant(8,314j/gas constant(8,314j/Kmol)Kmol),, T: T: temperaturetemperature(K)(K)

Isochoric ProcessIsochoric Process

Process in which volume is kept constant.Process in which volume is kept constant.

““Mathematical analysis Mathematical analysis of isochoric process”of isochoric process”

dEi = (dEi = (u/u/T)T)VVdT + (dT + (u/u/V)V)TTdV = dQ + P.dVdV = dQ + P.dV

For isochoric processFor isochoric process dV = 0dV = 0

=>=> ( (u/u/T)T)VVdT = dQ = CdT = dQ = CVV.dT .dT

CCVV : : specific heat of System in isochoric processspecific heat of System in isochoric process

For n moles of gasesFor n moles of gases,,

n. n. Ei = qEi = qVV = n.C = n.CVV.dT.dT

Thus, for an isochoric process heat energy is Thus, for an isochoric process heat energy is absorbed by the system to increase internal energy.absorbed by the system to increase internal energy.

Isobaric ProcessIsobaric Process process in which pressure is kept constantprocess in which pressure is kept constant

dEdEii = dQ - dW = dQ - dW

dQ = dEdQ = dEii + dW = dE + dW = dEii + P.dV + P.dV

Isobaric situations:Isobaric situations:

dQdQPP=dE=dEii + d(P.V) = d(E + d(P.V) = d(Eii + P.V) = dH + P.V) = dH

=> Enthalpy:=> Enthalpy: H = EH = Eii + P.V + P.V

dQdQPP = dH = dH

QQPP = H = H

These equations result in a conclusion that:These equations result in a conclusion that:““Change in heat energy amount is equal to the Change in heat energy amount is equal to the enthalpyenthalpy””

Isobaric Process (Continuing)Isobaric Process (Continuing)

dH = CdH = CPP.dT.dT

CCPP: : specific heat at isobaric processspecific heat at isobaric process

For n moles of gases:For n moles of gases:

dH = n.CdH = n.CPP.dT.dT

Isobaric Process (Continuing)Isobaric Process (Continuing)

EnthalpyEnthalpy

Consider the Consider the EnthalpyEnthalpy with the with the Ideal Gas Law:Ideal Gas Law:

H = Ei + P.V = Ei + R.TH = Ei + P.V = Ei + R.T

Take the derivative of above equation:Take the derivative of above equation:

dH = dEi + R.dTdH = dEi + R.dT

The resultant equation indicates that:The resultant equation indicates that:

““Internal Energy of ideal gas is only dependent Internal Energy of ideal gas is only dependent onon T” T”

Consider the other equations together:Consider the other equations together:

CCPP.dT = C.dT = CVV.dT + R.dT.dT + R.dT

CCPP = C = CVV + R + R

=> => R = CR = CPP – C – CVV

Enthalpy (Continuing)Enthalpy (Continuing)

Isothermal ProcessIsothermal Process processprocess in which temperature is held constant in which temperature is held constant Examples: Ideal gases & ideal paramagnetic crystalsExamples: Ideal gases & ideal paramagnetic crystals

For an adiabatic system:For an adiabatic system:

ΔΔQ = 0Q = 0

ΔΔEEii = = ΔΔQ + Q + ΔΔW => W => ΔΔEEi i = = ΔΔWW

If the system is compressedIf the system is compressed

EEi i = - W= - W (internal energy ↑, Work is -)(internal energy ↑, Work is -) If the system is expandedIf the system is expanded

- E- Ei i = W= W (internal energy ↓, Work is +)(internal energy ↓, Work is +)

Adiabatic Process (Continuing)Adiabatic Process (Continuing)

Adiabatic ProcessAdiabatic Process Process in which no heat transfer takes placeProcess in which no heat transfer takes place Cork, mineral wool, isolated glass must be Cork, mineral wool, isolated glass must be

used to isolate the systemused to isolate the systemOr;Or;The process should be completed immediately.The process should be completed immediately.

Second Law of ThermodynamicsSecond Law of Thermodynamics

i. states in which direction a process can take placei. states in which direction a process can take place

heat does not flow spontaneously from a cold to a hot bodyheat does not flow spontaneously from a cold to a hot body

heat cannot be transformed heat cannot be transformed completelycompletely into mechanical work into mechanical work

it is impossible to construct an operational perpetual motion it is impossible to construct an operational perpetual motion machinemachine

ii. introduces concept of ii. introduces concept of entropyentropy

Second Law of ThermodynamicsSecond Law of Thermodynamics

““It is impossible for any device that operatesIt is impossible for any device that operates

on a cycle to receive heat from a singleon a cycle to receive heat from a single

reservoir and produce a net amount of work.”reservoir and produce a net amount of work.”

22ndnd Law Statement By Kelvin-Planck Law Statement By Kelvin-Planck

To have such a cycle another reservoir withTo have such a cycle another reservoir with

different temperature is needed.different temperature is needed.

Second Law of Thermodynamics (Continuing)Second Law of Thermodynamics (Continuing)

Reversible and Irreversible Reversible and Irreversible ProcessesProcesses

Irreversible Process:Irreversible Process:

““Once having taken place , these processes can not Once having taken place , these processes can not

reverse themselves spontaneously and restore thereverse themselves spontaneously and restore the

system to its initial state.”system to its initial state.”

For Example,For Example,

Once a cup of hot coffee cools, it will not heat up byOnce a cup of hot coffee cools, it will not heat up by

retrieving the heat it lost from the surroundings.retrieving the heat it lost from the surroundings.

Reversible Process:Reversible Process:

““A process that can be reversed without leavingA process that can be reversed without leaving

any trace on the surroundings.”any trace on the surroundings.”

This is possible only if the net heat and net work This is possible only if the net heat and net work

exchange between system and surroundings is zeroexchange between system and surroundings is zero

for the combined (original and reverse) process.for the combined (original and reverse) process.

EntropEntropyy

property that indicates the direction of a processproperty that indicates the direction of a process

Entropy ,Entropy ,

is a measure of disorderis a measure of disorder

is a measure of a system’s ability to do useful workis a measure of a system’s ability to do useful work

determines direction of timedetermines direction of time

Entropy (S) equation:Entropy (S) equation:

S = Q/TS = Q/T or or ΔΔS = S = ΔΔQ / TQ / Tsystemsystem

Q: Q: heatheatT: T: Abs. Temp.Abs. Temp.

Unit Analysis:Unit Analysis:

[Cal]/[˚K][Cal]/[˚K][Cal[Cal/mol/mol]/[˚K]]/[˚K] (for molar entropy)(for molar entropy)

For example: For example: An ice An ice (crystalline) molecules are strongly order(crystalline) molecules are strongly orderSo, the Entropy is small for ice.So, the Entropy is small for ice.

Ice Ice →(heat) → Water (→(heat) → Water (liquid)liquid)That is, the strong (crystalline) structure is broken.That is, the strong (crystalline) structure is broken.So, the Entropy increases.So, the Entropy increases.

Water (liquid) →(heat)→ Vapor (gas)Water (liquid) →(heat)→ Vapor (gas)Gas molecules are more unordered.Gas molecules are more unordered.That is to say “the Entropy increases more”.That is to say “the Entropy increases more”.

The example can be concluded as this;The example can be concluded as this;

““Entropy is increased by the energy given to the Entropy is increased by the energy given to the system”system”

Relationship bw. the Relationship bw. the changechange in in Energy & Entropy Energy & Entropy of of SystemSystem::

ΔS ΔS >> ΔQ/T ΔQ/T

Some examples for entropy changeSome examples for entropy change If ordered system If ordered system →→an independent system, an independent system,

Entropy Entropy ↑↑..The reverse cause Entropy The reverse cause Entropy ↓↓..

If If solidssolids and and liquidsliquids reacts a reacts a gasesgasesEntropy Entropy ↑↑..The reverse cause Entropy The reverse cause Entropy ↓↓..

If a Volume If a Volume ↑↑, Entropy , Entropy ↑↑..If a Volume If a Volume ↓↓, Entropy , Entropy ↓↓..

Standard Absolute Entropy:Standard Absolute Entropy:

Change in Entropy, caused by the increase inChange in Entropy, caused by the increase in

temperature of pure crystals, in isobaric conditions,temperature of pure crystals, in isobaric conditions,

from 0K to 298K.from 0K to 298K.

Entropy of Reaction:Entropy of Reaction:

Change in Entropy of system Change in Entropy of system

in isobaric and isothermal conditions,in isobaric and isothermal conditions,

for chemical reactions in which maximum offor chemical reactions in which maximum of

reaction parameter is 1 mole.reaction parameter is 1 mole.

Entropy is dependent of three parameters:Entropy is dependent of three parameters:

TemperatureTemperature

PressurePressure

Reaction variableReaction variable

S = f(T,P,ξ)S = f(T,P,ξ)

T:T: absolute temperature absolute temperature,,

P: P: pressure, pressure,

ξ: reξ: reaction variable.action variable.

Free EnergyFree Energy

(also known as (also known as Gibbs’ Energy Gibbs’ Energy oror usefuluseful energy energy))

In biological systems In biological systems Free EnergyFree Energy concept concept is the is the best method for explaining the energybest method for explaining the energy conversionsconversions..

EExplains the usable component of system’s total xplains the usable component of system’s total

energy under isobaric and isothermic conditions. energy under isobaric and isothermic conditions.

TThe he CConcept of oncept of FFree ree EEnergynergy

CCombinombinee the the 11stst and and 22ndnd laws of thermodynamic laws of thermodynamics:s:

ΔEΔEii = ΔQ – P. ΔV, = ΔQ – P. ΔV, ““ΔQ = T. ΔS”ΔQ = T. ΔS”

=>=> ΔE ΔEii = T.ΔS – P. ΔV = T.ΔS – P. ΔV

ΔEΔEii + P. ΔV – T. ΔS = ΔG, + P. ΔV – T. ΔS = ΔG, ““ΔEΔEi i + P. ΔV = ΔH+ P. ΔV = ΔH””

=>=> ΔH – T. ΔS = ΔG ΔH – T. ΔS = ΔG H: enthalpy H: enthalpy ΔH: change in enthalpyΔH: change in enthalpy

ForFor the the reaction entropy conditionsreaction entropy conditions;;

PP & T are & T are constantconstants.s.

ThenThen::

G = Ei + P.V – T.SG = Ei + P.V – T.S

By this formula the By this formula the free energyfree energy can be calculated. can be calculated.

In a reaction, the change in free energyIn a reaction, the change in free energy

can be can be zerozero, , positivepositive or or negativenegative value. value.

The The signsign of free energy change determines the of free energy change determines the direction of reactiondirection of reaction. .

The condition that free energy change isThe condition that free energy change is;;

ZZero ero (ΔG = 0),(ΔG = 0), indicates the indicates the equilibrium stateequilibrium state. .

NNegative egative (ΔG < 0),(ΔG < 0), explains that the reaction explains that the reaction

has occurred by has occurred by giving energy to the environment. giving energy to the environment.

PPositive ositive (ΔG > 0)(ΔG > 0),, indicates indicates the system has the system has taken taken

energy from the environmentenergy from the environment during the reaction. during the reaction.

RadiationEnergy (photons)

water

oxygen

carbon dioxide

Chemical energy of carbohydrates and other products of cells

Thermal and other energies

Chemical energy

Biological energy

Biological EnergyBiological Energy

FlowFlow

4H4H→→He + 2e + enerjiHe + 2e + enerji

TThree hree main main stepssteps of of Biologic Biologic EEnergy nergy FFlowlow::

I.I. SSolar energy olar energy → → OOrganic rganic MMaterialsaterials (by ototrof organisms)(by ototrof organisms)

II.II. OOrganic rganic MMaterials aterials → → ATP ATP (energy) (energy) ((by respirationby respiration))

III.III. ATPATP → → other forms of energyother forms of energy (by (by biological processesbiological processes))

PhotosynthesisPhotosynthesis & Respiration & Respiration

PhotosynthesisPhotosynthesis: : CConversion of onversion of solar energy solar energy (photons)(photons) into into chemical energychemical energy with with chlorophyllchlorophyll by the by the green plantsgreen plants..

((ChlorophyllChlorophyll))

6CO6CO22 + 6H + 6H22O + n.h.f. O + n.h.f. C C66HH1212OO66 + 6O + 6O22

n: n: Planck constantPlanck constant ( (6,62.10-34 j.s6,62.10-34 j.s)) h: h: photon frequencyphoton frequency f: f: number of photons in the reactionnumber of photons in the reaction

During photosynthesisDuring photosynthesis;;

FFree energy ree energy change: change: GGss = 2867 kj/mol = 2867 kj/mol

““glucose formation needs energyglucose formation needs energy””

““28286767 kJ solar energy is used for each glucose mole kJ solar energy is used for each glucose mole””

EEnthalpy nthalpy change: change: HHss = 2810 kj/mol = 2810 kj/mol

EEntropy changentropy change: : SSss = - 182 j/(mol)K = - 182 j/(mol)K

““reaction is endothermicreaction is endothermic””

The inverse mechanism of photosynthesis is The inverse mechanism of photosynthesis is called called rrespirationespiration..

CC66HH1212OO66 + 6O + 6O22 6CO6CO22 + 6H + 6H22OO

((GlucoseGlucose) )

During During respiration;respiration;

FFree energy ree energy change: change: GGss = = --2867 kj/mol2867 kj/mol

EEnthalpy nthalpy change: change: HHss = = --2810 kj/mol2810 kj/mol

EEntropy changentropy change: : SSss = 182 j/(mol)K = 182 j/(mol)K

““reaction is ereaction is exxothermicothermic””

In heterotrophic organisms the energy In heterotrophic organisms the energy ofof the the nutrients’ itselfnutrients’ itself is gained again as a result of is gained again as a result of cellular cellular respirationrespiration ((oxidationoxidation).).

AAndnd,, this energy is used for the this energy is used for the synthesis of synthesis of ATP moleculeATP molecule. .

ADP + PADP + Pİİ ATP + H ATP + H22OO

((Inorganic phosphateInorganic phosphate))

ΔG = + 30.5 kj/molΔG = + 30.5 kj/mol

OOnly some part of the energy obtained from nly some part of the energy obtained from oxidation is oxidation is used for ATP synthesisused for ATP synthesis; ;

the other part is given to the environment of the other part is given to the environment of cell cell as heat energyas heat energy. .

Energy released, while the conversion of ATP Energy released, while the conversion of ATP to ADP and inorganic phosphate in the cell, is to ADP and inorganic phosphate in the cell, is used for the cell’s vital functionsused for the cell’s vital functions..

ATP + HATP + H22O O ADP + P ADP + Pİİ

ΔG = - 30.5 kj/molΔG = - 30.5 kj/mol

What could aWhat could a cell do with hydrolysis cell do with hydrolysis of of ATP ATP??

BiosynthesisBiosynthesis: Formation of bigger molecules : Formation of bigger molecules from smaller molecules.from smaller molecules.

Active TransportActive Transport: Transport of molecules : Transport of molecules against the concentration gradient of cell against the concentration gradient of cell membrane.membrane.

MechanicMechanicalal Work Work: Contraction of muscle cells.: Contraction of muscle cells.

Energy Distribution In Energy Distribution In Biomolecular SystemsBiomolecular Systems

Typical Heat EngineTypical Heat Engine Needs high Temperature differences to work.Needs high Temperature differences to work. Energy transformations done toward the balance.Energy transformations done toward the balance.

So, it works with decreasing Entropy.So, it works with decreasing Entropy.

However, Livings Energy transformationsHowever, Livings Energy transformations held on with constant temperatureheld on with constant temperature Direction of energy transformation is away from balanceDirection of energy transformation is away from balance

So, increasing Entropy is needed. So, increasing Entropy is needed.

AAdenosinedenosine--tritri--phosphate(ATP) phosphate(ATP) is the is the EnergyEnergy storage molecule.storage molecule. It is It is made by breaking down nutrients in mitochondrmade by breaking down nutrients in mitochondriaiae, e,

By the By the oxidationoxidation of 1 mol of 1 mol glucoseglucose 18 mol 18 mol ATPATP is is producedproduced. .

AAdenosinedenosine--tritri--phosphate is phosphate is hydrolizedhydrolized with with enzymesenzymes to to form form AAdenosinedenosine--didi--phosphate (ADP) phosphate (ADP) →→AAdenosinedenosine--monomono--

phosphate (AMP). phosphate (AMP).

TThe energy coming out is consumed in needed he energy coming out is consumed in needed places inside cell.places inside cell.

EnzymesEnzymes

Enzymes have great role in events occuring inside the cell.Enzymes have great role in events occuring inside the cell.

Enzymes Enzymes are are consist of long protein chainsconsist of long protein chains..

““Enzymes acts like a Enzymes acts like a metabolic catalizorsmetabolic catalizors””

Enzymes act with the reactants to produceEnzymes act with the reactants to produce intermediateintermediate products having lower products having lower activation energyactivation energy ; ;

So that total So that total activation energyactivation energy of reaction decreases. of reaction decreases.

Thus, reactions go on as steps requThus, reactions go on as steps requiire lesser energy.re lesser energy.

Hydrolisis of ATPHydrolisis of ATP ((by effect of enzymesby effect of enzymes))

ATPATP4-4- + H + H22O O ADP ADP3-3- + HPO + HPO442-2- + H + H++

The Gibbs The Gibbs ((freefree)) energy change of this process: energy change of this process:

GGØØ = -30 kj/mol (pH = 7) = -30 kj/mol (pH = 7)

Meanwhile, (-) of sign of the Meanwhile, (-) of sign of the GibbsGibbs energy change energy change

shows that a 30 - kj/mol energy is shows that a 30 - kj/mol energy is releasedreleased..

Some Terms for Biochemical ReactionsSome Terms for Biochemical Reactions

Cell components continuosly synthesized and Cell components continuosly synthesized and destroyed are called destroyed are called metabolitesmetabolites. .

Cellular reactions called Cellular reactions called metabolismmetabolism are divided are divided into two groupsinto two groups::

cataboliccatabolic (being broken)(being broken) reactionsreactions..

anabolicanabolic (being synthesized)(being synthesized) reactionsreactions..

Series of reactionsSeries of reactions occuring in a spesific occuring in a spesific

arrangement are called arrangement are called metabolic waysmetabolic ways..

May beMay be linear, circular, helicallinear, circular, helical or or branchedbranched shape. shape.

CCatalysis of enzymesatalysis of enzymes is needed is needed to to performperform metabolicmetabolic waysways..

((at at pressure, temperature pressure, temperature andand pH pH conditions conditions for a for a cellcell))

NNucleoside triphosphateucleoside triphosphate and and nicotinamidenicotinamide coenzymescoenzymes play a role as play a role as energy carriersenergy carriers..

Organism, divides the nutrients into smaller pieces Organism, divides the nutrients into smaller pieces by using by using catabolic reactionscatabolic reactions. .

The energy (HThe energy (H++ + e + e--) gained during this reaction is ) gained during this reaction is transferred by energy carrier molecules (ATP, transferred by energy carrier molecules (ATP, GTP, UTP, etc.).GTP, UTP, etc.).

GlucoseGlucose, , fatty acidsfatty acids and some and some amino acidsamino acids, after , after passing to blood, reaches the cell passing to blood, reaches the cell ((by some by some

mechanisms or by osmosis.mechanisms or by osmosis.)) These molecules turn into These molecules turn into acetyl-CoAacetyl-CoA by oxidation by oxidation,,

and and

this procedure is called this procedure is called glycolysisglycolysis. .

Acetyl-CoAAcetyl-CoA acts on the acts on the citric acid cyclecitric acid cycle, and , and

the the energy (Henergy (H+ + + e+ e--) gained ) gained fromfrom of of nutrientsnutrients is held by: is held by:

i.i. nucleosidnucleosidttriphofphate (ATP, GTP)riphofphate (ATP, GTP),, and and

ii.ii. reduced coenzymes (NADH, FADHreduced coenzymes (NADH, FADH22).).

Reduced coenzymes synthesiReduced coenzymes synthesizeze ATP, by the way of ATP, by the way of

ooxidative phosphorylation mechanismxidative phosphorylation mechanism::

ADP + PADP + Pi i →→ ATPATP

Catabolic and anabolic reactions are under the Catabolic and anabolic reactions are under the control of cellcontrol of cell..

So that the synthesized energy is used economically.So that the synthesized energy is used economically.

Cellular control mechanism controls the entrance Cellular control mechanism controls the entrance and exit of metabolitesand exit of metabolites strictly strictly..

So that So that metabolic ways work with in an harmony.metabolic ways work with in an harmony.

In an eukaryotic cell 50000 enzymes control many In an eukaryotic cell 50000 enzymes control many reactions at the same time. reactions at the same time.

This is a thermodynamic This is a thermodynamic miraclemiracle for the survival for the survivalss..

Feed–back inhibition and feed-forward Feed–back inhibition and feed-forward

activation mechanisms take the control of cell.activation mechanisms take the control of cell.

Since Since multi-cellular organismsmulti-cellular organisms have specific have specific

cells for each tissue, they need additional cells for each tissue, they need additional

metabolic control systems such as metabolic control systems such as hormoneshormones

and and other factorsother factors..

MMetabolic etabolic RReactionseactions

RRequired for equired for transfer transfer of substance of substance and energyand energy, and, and AAlways lways occuroccur according to according to the the laws of laws of thermodynamicthermodynamicss..

TTransferransfer of substance of substance means migration of atoms. means migration of atoms.

But the But the ttransferransfer of of energyenergy is the formation of a new product is the formation of a new product within the conclusion of reaction.within the conclusion of reaction.

TTake place in the ake place in the stable environmentstable environment; ;

Therefore, cell is a stable environmentTherefore, cell is a stable environment..

The concentration level of The concentration level of reacting reacting metabolitesmetabolites and and resulting productsresulting products is kept in the same level. is kept in the same level.

FFree energy change (∆G) and standard free energyree energy change (∆G) and standard free energy

change (∆Gchange (∆GΦΦ) are different concepts.) are different concepts.

BecauseBecause, the free energy, , the free energy, needed for any reactionneeded for any reaction occur occur in a cellin a cell, depends on:, depends on:

i.i. concentration of concentration of reacting metabolitesreacting metabolites, , andand

ii.ii. concentration of concentration of resulting productsresulting products..

““When the free energy change is When the free energy change is negativenegative, the , the reaction takes place suddenly.” reaction takes place suddenly.”

FFormula ormula of rof reaction’s standard free energy change:eaction’s standard free energy change:

∆∆GGΦΦ = - R.T = - R.T..ln ln ((KKeqeq))

In cellular reactions concentrations of In cellular reactions concentrations of reacting reacting substancessubstances and and resulting resulting productsproducts usually reaches usually reaches equilibrium stateequilibrium state,,

TThese reactions are called hese reactions are called near equilibriumnear equilibrium reactions. reactions.

If concentration levels are away fromIf concentration levels are away from equilibrium, equilibrium,

these reactions are called these reactions are called irreversible reactionsirreversible reactions. .

ATP ( Adenosine-tri-phosphate )ATP ( Adenosine-tri-phosphate )

ATPATP is the key factor in energy metabolism. is the key factor in energy metabolism.

EnergyEnergy,, formed as a result of biological proceduresformed as a result of biological procedures,, is is kept in the kept in the ATPATP to be used in to be used in other other biological system.biological system.

ATP molecule transfers its ATP molecule transfers its last phosphoric grouplast phosphoric group and and nucleotide groupnucleotide group to form energy. to form energy.

The The adenilate kinase enzymeadenilate kinase enzyme in the cell keeps ATP in the cell keeps ATP concentration constantconcentration constant..

There is There is 250 mg250 mg ATP in an adult ATP in an adult,, andand one spends one spends 50 kg50 kg ATP in a day, ATP in a day,

““SSo one can guess how great the metabolic activity iso one can guess how great the metabolic activity is ..””

The energy obtained from oxidation reactions of the The energy obtained from oxidation reactions of the molecules is consumed to reduce NADmolecules is consumed to reduce NAD++,, So that So that NADH is heldNADH is held..

Energy Energy of of reduced coenzymes is calculated by reduced coenzymes is calculated by reduction reduction potentialpotential which expresses which expresses ability of ability of moleculemolecules to give s to give electronselectrons. .

RRelationship between standard reduction and standard elationship between standard reduction and standard free energy changefree energy change:: ((by Nerstby Nerst))

∆∆G = - n.F. ∆EG = - n.F. ∆EΦΦ

In the equationIn the equation:: n: n: number of transferred electronsnumber of transferred electrons.. F: F: Faraday constant (96500 C)Faraday constant (96500 C) ∆∆EEΦΦ: : Reduction potentialReduction potential

Energy Need of Human BodyEnergy Need of Human Body

Metabolic rateMetabolic rate::TThe energy that should be used for a certain work he energy that should be used for a certain work for for a a unit surfaceunit surface and in a and in a ununitit time time..

““Metabolic Metabolic raterate is usually same in all people is usually same in all people””.. Basal metabolic rateBasal metabolic rate (BMR) (BMR)::

TThe rate he rate of eof energy nergy consumption to consumption to keepkeep the the temperature constantemperature constantt, , to keep upto keep up circulation, circulation, respirationrespiration,, and other life activities and other life activities ofof a person who a person who is at is at restrest, , not doing any needless worknot doing any needless work, , lying and lying and awakeawake..

Typically, Typically, BMRBMR is is calculated as:calculated as:

BMR = 170 kj/mBMR = 170 kj/m22.hour = 47 W/m.hour = 47 W/m22

If a person’s If a person’s mass (m) kg ;mass (m) kg ; height (h) m ; height (h) m ;

Then, Then, surface area can be calculatedsurface area can be calculated::

A = 0,202 A = 0,202 .. m m0,4250,425 .. h h0,7250,725 (m (m22))

Some activities of human and correspondingSome activities of human and correspondingmetabolic ratesmetabolic rates and and daily effortsdaily efforts::

  Metabolic Rate Corresponding Daily effort

 kj/hour W/m2 Time(hour) energy

(kj/m2)

sleep

146 41 8 1172

Eating,drinking,wearing

418 116 3 1255

Reading, writing 251 70 4 1004

Medium physical work 628 174 8 5021

Hard exercise 1256 349 1 1255

Total 24 9707

Unit Calorie Unit Calorie EquationEquation of Nutrients of Nutrients

Some of the Some of the caloriecalorie equation of nutrıents for human: equation of nutrıents for human:

Carbonhydrates 4.1 Kcal/g

Proteins 5.3 Kcal/g

Lipids 9.2 Kcal/g

Alcohol 7.0 Kcal/g

Energy amountEnergy amount that can be taken from a that can be taken from a unit massunit mass of nutrients is of nutrients is differentdifferent for each of them.for each of them.

HoweverHowever,,

IIt is knownt is known that that consumption of consumption of 1 lt 1 lt OOxygenxygen requires production of requires production of 20209 J20209 J (4830cal)(4830cal) energyenergy. .

ThusThus, , metabolic ratesmetabolic rates of different activities are of different activities are found by found by measuringmeasuring the the consumption of Oxygenconsumption of Oxygen..

IIncreasncreas in in temperaturetemperature = = 1°C 1°C => => metabolic ratemetabolic rate increasesincreases by by %10%10..

When When surplussurplus of some substances enters in body, it is of some substances enters in body, it is taken out of bodytaken out of body via several ways via several ways;;

BButut,, the the surplussurplus of the calories of the calories can can notnot be removed be removed easily.easily.

These These extra caloriesextra calories are especially stored as are especially stored as lipidlipidss with with additional tissues.additional tissues.

IfIf there there existsexists a decrease in a decrease in energy energy entries of the body:entries of the body:

i.i. ItIt consumesconsumes its own its own lipidlipids s firstfirst, , ii.ii. thenthen if necessary if necessary it it consumesconsumes proteinsproteins..