Andrew Abraham BSCI207 – Higgins Fall 2011Lecture 2 – ThermodynamicsThermodynamics- How all organisms get the job done- The study of the inter-relation between heat, work and internal energy of a systemEnergy- The capacity to do work or to supply heatWhy talk about energy now?- There is no life without energy life depends on the continuous input of energyo Food sources provide both (1)energy that can be converted to forms of generally useful biological reactions and (2) molecular structures that can be used to make macromoleculeso Energy for all life originates from the sun Light is converted into chemical energy (organic molecules) in the presence of water and minerals Some energy is used to make more biomass (plants) to sustain animal life, provide energy to grow and do work Some energy is lost as heat and waste molecules Most effective way to make chemical energy is through respirationEnergy and Evolution- All organisms require a source of energy to combat entropy and maintain an ordered system- Organisms are able to inhabit an environment by evolving a means or utilizing the energy source(s) available there- Evolution – change through time- We will begin by examining energy and the physical laws that describe and govern its acquisition and useEx. Rifitia (Tubeworm); symbiotic bacterium - Thiovulum- 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?o Photosynthesis vs. Chemosynthesis Photosynthesis – the use of solar energy to make organic matter- Sum gives off energy in the form of light- Plants absorb sunlight and take up water from the soil and CO2 from the air- The plants use their solar energy to make organic molecules (sugars)- The plants release oxygen into the air (6CO2 + 6H2O + energy C6H12O6 + 6O2).The plants grow and reproduce, and are eaten or hosted as internal symbionts by animals Chemosynthesis – the use of energy released by inorganic chemical reactions to produce food- Hydrothermal fluid coming out of vents contains hydrogen sulfide- Microbes living around the vents take up hydrogen sulfide, oxygen, and carbon dioxide from the water- The microbes get energy by breaking down the hydrogen sulfide. They use this energy and oxygen to convert CO2into sugars- The microbes release sulfur and waterEnergy Acquisition- Summary: Organisms obtain useful energy from light or by oxidizing substrate molecules found in the environmento Electron Potential energy Greatest potential energy is in outermost shell since the electrons are furthest away from the protons located in the nucleus As the electron falls to a lower energy shell, its potential energy is converted to kinetic energyTypes of Work- Synthetic, Mechanical, Concentration, Electrical, Heat production, BioluminescenceEnergy: Potential (stored energy) and Kinetic (energy of motion)- 1st Law of Thermodynamics – Energy cannot be created or destroyed, but only transferred and transformed; “Law of Conservation of Energy)o Efficiency is the thing for organismso Describes energy interconversionso Specifies energy balances, not reaction direction or rateo ∆U = Q + W ∆U = Change in internal energy Q = Heat added to the system W = Work done by the system- 2nd Law of Thermodynamics – Entropy is always increasing in an isolated systemo Life is all about combating the inevitable increase in Entropy!o The entropy of an isolated system which is not in equilibrium will tend to increase over time, approaching a maximumvalue at equilibrium Every energy transfer or transformation increased the entropy of the universe; “10% Rule” It turns out that for a process to occur on its own, without outside help (input of energy), it must increase the entropy of the universeo ∆S > 0 and ∆S = ∆Q/T The entropy of the Universe never decreases. It either increases (for irreversible processes) or remains the same (for reversible processes)Explosion of H2 Gas (2 H2 + O2 2 H2O)- Exactly how did it occur?o Sharing of electrons in new bondso Requires energy of activation to excite the electrons oEnthalpy (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, heat is taken in endothermicWhat makes a chemical reaction spontaneous?- Chemical reactions are spontaneous if they proceed on their own, without anycontinuous external influence such as added energy; they must also increase entropy- Two factors that determine whether a reaction is spontaneous or nonspontaneous o Reactions tend to be spontaneous if the products have lower potential energy thanthe reactants Reaction products have lower potential energy if their electrons are held more tightly than are the electrons of the reactants The difference in potential energy between reactants and products is given off as heat reaction is exothermic (∆H is negative) Difference in potential energy between the products and the reactants is symbolized by ∆H (heat)o Reactions tend to be spontaneous when the product molecules are less ordered than the reactant molecules (increase entropy) The amount of disorder in a group of molecules is called it entropy (∆S) When the products of a chemical reaction are less ordered than the reactant molecules are, entropy increases and ∆S is positiveTwo 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)o Endergonic (input in energy) vs. exergonic (release of energy)Does this reaction occur? Does it occur spontaneously?- Entropy (S): is it increasing?- Enthalpy (H): is it giving off heat energy?- G = H - TS; G is Gibbs Free EnergyFree Energy- Will the following reaction occur? C6H12O6 + 6O2 6CO2 + 6 H2O + energyo G or Gibbs Free Energy is negative for this reaction - thus it will bespontaneous- Gibbs Free Energy for s spontaneous reaction o Glucose + 6O2 6CO2 + 6 H2Oo 2 H2 + O2 2 H2Oo CH4 + 2O2 CO2 + 2H2O H is negative (heat energy is released!) for all three reactions Reaction is
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