Biology 140 notes Feb 17, 2009

Energy and Thermodynamics Thermo- heat dynamics- force or movement 3 laws of thermodynamics that we use right now in the world. Work: the process of moving an object against a force, Energy: the capacity to do work; to bring about movement against an opposing force. These occur on the phospholipids bilayer. Two types of energy: Potential energy ? stored energy; available for later use (can be found in bonds), Kinetic energy ? energy in current use. The first Law of Thermodynamics: The total amount of energy in the universe remains constant. Energy is neither lost nor gained, only transformed. The second Law of Thermodynamics: The amount of energy available to do work is constantly decreasing. Reactions will run spontaneously only in a direction from higher order (and energy) to lower order (and energy). Spontaneously means that something will happen all by itself without any energy in science terms. When energy is transferred to a different form it loses some energy in the form of heat. Heat is defined as disordered energy it is just a random form of molecules. Heat is not biologically useful cannot be used for biological functions. The concept of Entropy: Entropy is a measure of the amount of disorder in a system (the 2nd law says that entropy will always increase.) I.e. when disorder increases entropy increases 3rd law of thermodynamics: Has to do with the concept of absolute zero and the complete absence of heat. The 2nd Law of Thermodynamics applies to a closed system (Earth) an open system would be the Sun. There is a constant input of energy from the sun Biological activity brings about local increases in order. ?Free Energy? (designated ?G?) is a measure of the energy available in the chemical bonds of a molecule that is available to do work. G- Free energy, ?G ? The change in free energy from an initial to a final state. ?G is calculated as follows ?G = GProducts ? GReactants For a reaction to occur spontaneously in a closed system, the energy of the products must be less than the energy of the reactants. That is, the Delta G must be negative That is, less energy remains for work after the reaction That is, the products (low energy) are more stable than the reactants (high energy). Exergonic Reaction ? The free energy of the products is less than that of the reactants; energy has been released (?energy out?) (Is ?Downhill? or ?spontaneous? is the way thermodynamics wants to go) Endergonic Reaction ? The free energy of the products is more th an that of the reactants energy has been gained or stored (energy in) (Is uphill? ?Fights? the 2nd law of thermodynamics all though the 2nd law does allow this so it?s not really fighting it per se. ATP = adenosine triphosphate ?energy currency of the cell? energy storage molecule There is a tremendous amount of free energy stored in the bonds of an ATP molecule. This is the end products of glycolosis and respiration. It takes energy to store energy. Example being it takes energy to have a phosphate group adds to adenosine creating ATP. The energy in the phosphate bond is released in a hydrolysis reaction H2O + ATP ( ADP + Pi Change in G?? = -7.3 Kcal/mole The reaction is an exergonic reaction Free energy is released. Endergonic reaction = ATP Exergonic reaction = ADP Coupled reactions: both exergonic and endergonic reactions happening at the same time? ? That is, it takes energy to store energy (loading a spring). The 2nd law stipulates that the combined process is exergonic. We are using more energy (-?G) then we are storing (+?G). First law tells us: chemical energy released from ATP hydrolysis is exactly equal to mechanical work plus heat. Second Law tells us: Chemical energy released is greater than the amount of work done? because some of the energy is released as heat. Concentration gradient: A difference in Concentration of two substances represents potential energy, and has the potential to drive work. The 2nd law states that any process that converts an orderly arrangement to a less orderly arrangement can perform work (i.e. will have a ??G)