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Electron Transport Chain
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Electron Transport Chain

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Questions and Answers

What is the main concern of Bioenergetics?

  • The structure of ATP
  • The mechanisms of energy transfer
  • The initial and final energy states of reaction components (correct)
  • The entropy of reactants and products
  • What does the enthalpy (ΔH) measure?

  • The change in entropy of reactants and products
  • The change in randomness of reactants and products
  • The change in free energy of a chemical reaction
  • The change in heat content of reactants and products (correct)
  • What is the significance of a negative ΔG?

  • The reaction does not proceed spontaneously
  • The reaction is in equilibrium
  • The reaction proceeds spontaneously (correct)
  • The reaction does not release energy
  • What is the term for a reaction that does not proceed spontaneously?

    <p>Endergonic</p> Signup and view all the answers

    What is the approximate ΔG° of ATP hydrolysis?

    <p>-7.3 kcal/mol</p> Signup and view all the answers

    Why is ATP called a high-energy phosphate compound?

    <p>Due to its high free energy of hydrolysis</p> Signup and view all the answers

    What is the function of ATP in bioenergetics?

    <p>To transfer energy</p> Signup and view all the answers

    What is the significance of ΔG being zero?

    <p>The reaction is in equilibrium</p> Signup and view all the answers

    What is the term for the change in randomness or disorder of reactants and products?

    <p>Entropy</p> Signup and view all the answers

    What is the term for a reaction that proceeds spontaneously?

    <p>Exergonic</p> Signup and view all the answers

    Study Notes

    Electron Transport Chain

    • Specialized set of electron carriers located in the inner mitochondrial membrane, which facilitates the flow of electrons from different fuels to oxygen.
    • Consists of five separate protein complexes (I, II, III, IV, and V) in the inner mitochondrial membrane.
    • Each complex contains part of the electron transport chain, except for Complex V, which catalyzes ATP synthesis.

    Electron Transport Chain Components

    • With the exception of coenzyme Q, all members of the chain are proteins.
    • These proteins may function as enzymes, contain iron, be coordinated with a porphyrin ring, or contain copper.

    Reactions of the Electron Transport Chain

    • Formation of NADH: NAD+ is reduced to NADH by dehydrogenases, which remove two hydrogen atoms from their substrate.
    • NADH dehydrogenase: The free proton and hydride ion are transferred to NADH dehydrogenase (Complex I), which has a tightly bound molecule of Flavin mononucleotide (FMN) that accepts the two hydrogen atoms.
    • Coenzyme Q: Accepts hydrogen atoms from FMNH2 and FADH2, and transfers electrons to Complex III.
    • Cytochromes: Electrons are passed along the chain from coenzyme Q to cytochromes bc1 (Complex III), c, and a + a3 (Complex IV).
    • Cytochrome a + a3: This complex can react directly with molecular oxygen, forming water and releasing free energy.

    Free Energy Release during Electron Transport

    • Free energy is released as electrons are transferred along the electron transport chain from an electron donor to an electron acceptor.
    • The standard reduction potential (E) of a redox pair determines the tendency of the reductant member to lose electrons and the oxidant member to accept electrons.

    Bioenergetics/Biochemical Thermodynamics

    • Concerns the transfer and utilization of energy in biologic systems, focusing on the initial and final energy states of reaction components.
    • Enthalpy (ΔH): Measure of the change in heat content of reactants and products.
    • Entropy (ΔS): Measure of the change in randomness or disorder of reactants and products.
    • Free Energy Change (ΔG): Measure of the energetic feasibility of a chemical reaction, predicting the direction in which a reaction will spontaneously proceed.

    ATP as an Energy Carrier

    • ATP consists of a molecule of adenosine with three phosphate groups attached.
    • The standard free energy of hydrolysis of ATP, ΔG°, is approximately -7.3kcal/mol for each of the two terminal phosphate groups, making ATP a high-energy phosphate compound.

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    Quiz on the electron transport chain, a set of electron carriers in the inner mitochondrial membrane that facilitate the flow of electrons from different fuels to oxygen.

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