Energy Exchanges 1 st Law of Thermodynamics Energy

Energy Exchanges • 1 st Law of Thermodynamics – Energy cannot be created nor destroyed, energy is transferred from one form to another • 2 nd 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 2 nd 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 (CO 2 and H 2 O) and heat to environment

ENERGY EXCHANGES • Formula is ΔH = ΔG + TΔS ΔH = 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 From catabolism Endergonic energy for cellular work ΔG = -7. 3 kcal/mol ΔG = +7. 3 kcal/mol ADP + Pi

How ATP Works Type of Work Mechanical Transport Chemical Description • Beating cilia • Muscular contraction • Movement • Active transport • Pumps (H+ and Na+/K+) • Endergonic reactions • Polymerization

Coupled Reactions NH 2 GLU + NH 3 GLU + ATP GLU P + NH 3 ΔG = +3. 4 kcal/mol GLU P Not spontaneous ΔG = -7. 3 kcal/mol NH 2 ΔG = +3. 4 kcal/mol GLU ΔG = -3. 9 kcal/mol ------------- OVERALL RXN= ?