lec 2 - Thermodynamics: How all organisms get the job done....

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Unformatted text preview: Thermodynamics: How all organisms get the job done. Energy: The ability to do work or supply heat (page 30) Why talk about energy now? Tubeworm, Riftia Symbiotic bacterium, Thiovulum Riftia Has a unique hemoglobin that takes H2S from the environment and delivers it to the symbiotic Thiovulum 2H2S + O2 ---> 2So +2 H2O + energy How do these worms and other organisms capture or use this energy? http://www.divediscover.whoi.edu/vents/biology.html Types of Work Synthetic Mechanical Concentration Electrical Heat production Bioluminescence Energy: potential & kinetic Fig 2.15 Fig 2.16 1st Law of Thermodynamics: Energy cannot be created or destroyed, but only transferred and transformed (page 31) Efficiency is the thing for organisms! First Law of Thermodynamics Life's challenge transform available energy into useful forms at the right places and at the right times 1st Law describes energy interconversions 1st Law specifies energy balances, not reaction direction or rate www.wildnetafrica.com 2nd Law of Thermodynamics: Entropy is always increasing in a isolated system (page 32) magnonel.guild.net/~schwern/talks/ Refactoring/slides/slide007.html and now let us examine one of the only significant events to occur in the great state of New Jersey! 7:25 PM on 6 May 1937 Explosion of H2 Gas: 2 H2 + O2 ----> 2 H2O What do you know about that reaction from experience? BOOM! Light Heat Stable product EXACTLY how did it occur? Sharing of electrons in new bonds Requires energy of activation to excite the electrons Fig 3.21 Enthalpy: H H is the energy stored in the system or a molecule Heat content of bonds in a compound H = Hproducts - Hreactants When H is negative, heat is given off exothermic When H is positive, endothermic 2nd Law of Thermodynamics: Entropy is always increasing in a isolated system (page 32) Two factors determine the spontaneity of a reaction: Enthalpy: H (or energy released or required) Entropy: S (increase or decrease in order of system) The spontaneity of a reaction is expressed as the Gibbs Free Energy or G (the energy available to do work) Does this reaction occur? Does it occur spontaneously? Entropy (S) : is it increasing? Enthalpy (H): is it giving off heat energy? G = H - T S G is Gibbs Free Energy Free Energy Will the following reaction occur? C6H12O6 + 6O2 ---> 6CO2 + 6 H2O + energy G or Gibbs Free Energy is negative for this reaction - thus it will be spontaneous Gibbs Free Energy for a spontaneous reaction G = H - T S Negative & exothermic Positive & More disordered Glucose + 6O2 ----> 6CO2 + 6 H2O or 2 H2 + O2 ----> 2 H2O or CH4 + 2O2 ----> CO2 + 2H2O H is negative (heat energy is released !) Reaction is exothermic Glucose + 6 O2 <---- 6 CO2 + 6 H2O H is Positive Entropy is decreasing ! Reaction is endothermic Fig 2.18b What about this diffusion reaction? X is a solute molecule in water Membrane XX X X X X X X X X X X What about this diffusion reaction? Membrane Z+ Z+ Z+ Z+ Z+ Z+ Z+ Z+ Z+ Z+ Z+ What are the forces (potential energies at work here? C and E (voltage!) Z+ Z+ Z+ Z+ Z+ Z+ Z+ Z+ Z+ Z+ Z+ Reactions: reactants and products If the C (carbon) in an organic reactant molecule gains electrons, it is reduced If the C in an organic reactant molecule looses electrons, it is oxidized Fig 2.20: burning methane (CH4) Thinking about oxidation and reduction of Carbon compounds: (CH2O)6 + 6O2 <---> 6CO2 + 6H2O Carbon is OXIDIZED loses electrons Oxygen in REDUCED gains electrons Summary: Reactions of Living Organisms: C6H12O6 <---> 6CO2 + 6 H2O To the right, energy is liberated and carbon (C) loses electrons (and protons) and is thus oxidized To the left, energy is required, C gains electrons (and protons) and is reduced ...
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This note was uploaded on 04/22/2008 for the course BSCI 207 taught by Professor Higgins during the Spring '08 term at Maryland.

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