Energy Exchanges• 1st Law of Thermodynamics

– Energy cannot be created nor destroyed, energy is transferred from one form to another

• 2nd Law of Thermodynamics– Every energy transfer makes the universe more disordered– Entropy is a measure of this disorder– With every energy transfer, heat is lost– Amt of useful energy is decreased with every transfer

• PROBLEM: living organisms are highly ordered to decrease entropy – Question: Do living organisms violate 2nd Law?

ANSWER

• NO– Living organism is a closed system– Must consider organism and environment– Living organisms…

• Maintain highly ordered structure at expense of increased entropy of surroundings

• Take in complex high energy molecule, extract energy, release simpler, low energy molecules (CO2 and H2O) and heat to environment

ENERGY EXCHANGES

• Formula is ΔH = ΔG + TΔSΔH = change in enthalpy

= change in total energy

= heat of reaction

ΔG = change in free energy (Gibbs)

free energy is usable energy available to do work

TΔS = energy lost to the system

T= Temp. in Kelvin

ΔS = change in entropy

• During every energy exchange (ΔH) some energy is available to do work (ΔG) and some is lost to the system (TΔS)

Exergonic and Endergonic

EXERGONIC REACTIONS

• Reactants have more energy than products• More ordered to less• Unstable to stable• Downhill reaction• Free energy (ΔG) is released and is negative• Spontaneous• Ex: cellular respiration and digestion• LABEL: R, P, Energy and Time on graph

ENDERGONIC REACTIONS

• Products have more energy than reactants• Less ordered to more• Stable to unstable• Uphill reaction• Free energy absorbed from surroundings• ΔG is positive• Ex: photosynthesis, polymer synthesis• Label: R, P, Energy and Time on graph

COUPLED REACTIONS

• Energy released from exergonic reaction drives endergonic reaction

Exergonic ΔG = max work that can be done

Endergonic ΔG = min work needed to drive the reaction

When these two values are equal – most efficient

ATP Production

ATP

Exergonic energy Endergonic energy

From catabolism for cellular work

ADP + Pi

ΔG = +7.3 kcal/mol

ΔG = -7.3 kcal/mol

How ATP Works

Type of Work Description

Mechanical •Beating cilia•Muscular contraction•Movement

Transport •Active transport•Pumps (H+ and Na+/K+)

Chemical •Endergonic reactions•Polymerization

Coupled Reactions

NH2

GLU + NH3 GLU

ΔG = +3.4 kcal/mol

Not spontaneous

GLU + ATP GLU P ΔG = -7.3 kcal/mol

NH2

GLU P + NH3 GLU

ΔG = +3.4 kcal/mol

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ΔG = -3.9 kcal/mol

OVERALL RXN= ?