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Lecture 10-7 to 10-14 Energy metabolism

# Lecture 10-7 to 10-14 Energy metabolism - Energy Reducing...

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Energy Reducing Agents

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First law of thermodynamics : Energy can neither be created nor destroyed. The total energy in a system must remain constant. For example: chemical energy available in a metabolic fuel such as glucose is converted in the process of glycolysis to another form of chemical energy, ATP. In skeletal muscle chemical energy involved in energy-rich phosphate bonds of ATP may be converted to mechanical energy during the process of muscle contraction.
Second law of thermodynamics . Entropy: -Designated by S, is a measure of the degree of disorder or randomness in a system. - The energy in a system that is unavailable to perform useful work. - All processes, whether chemical or biological, tend to progress toward a situation of maximum entropy. For simplicity and because of its inherent utility in these considerations, a quantity termed free energy is employed. - The free energy (denoted by G or Gibbs free energy) of a system is that portion of the total energy in a system that is available for useful work. It is further defined by: delta G = the change in free energy delta H = the change in enthalpy or the heat content T = the absolute temperature delta S = the change in entropy of the system.

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Second law of thermodynamics : Entropy: delta G = the change in free energy delta H = the change in enthalpy or the heat content T = the absolute temperature delta S = the change in entropy of the system. --------------------------------------------------------------------------------------------------------------- - When delta G = 0, the process is at equilibrium. - Any process that exhibits a negative delta G (free-energy change) will proceed spontaneously toward equilibrium in the direction written, in part, due to an increase in entropy or disorder in the system (called an exergonic reaction) . - A process that exhibits a positive delta G will proceed spontaneously in the reverse direction as written. Energy from some other source must be applied to this process to allow it to proceed toward equilibrium (termed an endergonic reaction) .
Second law of thermodynamics : Entropy: delta G = the change in free energy delta H = the change in enthalpy or the heat content T = the absolute temperature delta S = the change in entropy of the system. -------------------------------------------------------------------------------------------------- The sign and value of delta G do not predict how fast the reaction will go. The rate of a given reaction depends on the free energy of activation but not on the magnitude of delta G .

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Second law of thermodynamics : Entropy: delta G = the change in free energy delta H = the change in enthalpy or the heat content T = the absolute temperature delta S = the change in entropy of the system. ------------------------------------------------------------------------------------------------------------------- The change in free energy for a chemical reaction is related to the equilibrium constant of that reaction. For example, an enzymatic reaction may be described as: and an expression for the equilibrium constant may be written as: We define the standard free energy at pH 7.0 ([H+] = 10 –7 M), where biological reactions generally occur. Under these conditions the change in free energy is expressed as delta G °’ and K ’eq. Since the value of delta G is zero at equilibrium, the following relationship is defined: R is the gas constant, which is 1.987 cal mol –1 K –1 ; and T is the absolute temperature in kelvin units (K).
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