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What are the general concepts of bioenergetics?

Enthalpy, entropy, free energy change, and standard free energy.

Which of the following is NOT a concept related to bioenergetics?

  • The mechanism of the reaction (correct)
  • The spontaneity of the reaction
  • The initial and final energy states of reaction components
  • The time needed for the reaction to occur (correct)

    • What is the universal energy carrier in biological systems?

  • Pyruvate
  • Glucose
  • Fatty acids
  • ATP (correct)

    • The structural basis of the high phosphate group transfer potential is found in the ______ of ATP.

    <p>triphosphate unit</p> Signup and view all the answers

    Which of the following is a phosphorylated compound with high phosphate group transfer potential?

    <p>All of the above</p> Signup and view all the answers

    ATP has the highest phosphate group transfer potential among the listed compounds.

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

    What are the factors that determine the direction of a chemical reaction?

    <p>Enthalpy, entropy, and temperature.</p> Signup and view all the answers

    Which of the following describes an endothermic reaction?

    <p>△H is positive.</p> Signup and view all the answers

    What is the definition of entropy?

    <p>Entropy is a measure of randomness or disorder of reactants and products.</p> Signup and view all the answers

    What happens to the entropy of a system when it becomes more ordered?

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

    Both enthalpy and entropy alone can predict the direction of a reaction.

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

    Describe Gibbs free energy.

    <p>Gibbs free energy is a thermodynamic property that correlates the enthalpy and entropy of a system, allowing prediction of the spontaneity of a reaction.</p> Signup and view all the answers

    What is the formula for calculating Gibbs free energy change (△G)?

    <p>△G = △H - T△S</p> Signup and view all the answers

    A negative △G indicates a non-spontaneous reaction.

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

    Which reaction is considered spontaneous based on Gibbs Free Energy change?

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

    What is the definition of standard free energy change (△G°)?

    <p>Standard free energy change (△G°) is the free energy change under standard conditions, where the reactant and product concentrations are kept at 1 M.</p> Signup and view all the answers

    Which of the following is the gas constant?

    <p>All of the above</p> Signup and view all the answers

    The signs of △G and △G° can be the same under all circumstances.

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

    △G° can be used to predict the direction of a reaction under non-standard conditions.

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

    What is the relationship between the equilibrium constant (K) and △G°?

    <p>The standard free energy change (△G°) is related to the equilibrium constant (K) by the equation: △G° = -RTlnK.</p> Signup and view all the answers

    If Keq=1, what does this indicate about △G°?

    <p>△G°=0</p> Signup and view all the answers

    If Keq>1, what does this indicate about △G°?

    <p>△G°&lt;0</p> Signup and view all the answers

    If Keq<1, what does this indicate about △G°?

    <p>△G°&gt;0</p> Signup and view all the answers

    What is transamination?

    <p>Transamination is a chemical reaction that involves the transfer of an amino group from one molecule to another.</p> Signup and view all the answers

    The equilibrium constant for most transamination reactions is close to 1.

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

    Under standard conditions, the reaction of glucose-6-phosphate to fructose-6-phosphate is

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

    Which of the following would make the reaction of glucose-6-phosphate to fructose-6-phosphate favorable (exergonic)?

    <p>Using fructose-6-phosphate immediately in the next step.</p> Signup and view all the answers

    What are the main sources of ATP in the body?

    <p>The two primary sources of ATP are substrate-level phosphorylation and oxidative phosphorylation.</p> Signup and view all the answers

    Red blood cells (RBCs) generate ATP primarily through oxidative phosphorylation.

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

    What is the relationship between △G and the transfer potential?

    <p>△G is equal to the transfer potential.</p> Signup and view all the answers

    There is an enzyme in cells capable of directly transferring phosphate from a high-energy donor to a low-energy acceptor.

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

    What is the ATP-ADP cycle?

    <p>The ATP-ADP cycle is a continuous process of energy exchange in biological systems, involving the formation of ATP from ADP and Pi, and the subsequent hydrolysis of ATP back to ADP and Pi, releasing energy for cellular processes.</p> Signup and view all the answers

    The ATP molecule is a long-term energy storage molecule.

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

    What are some examples of nucleotide analogs that drive biosynthesis reactions?

    <p>Guanosine triphosphate (GTP), cytidine triphosphate (CTP), and uridine triphosphate (UTP).</p> Signup and view all the answers

    What is the enzyme responsible for interconverting ATP and GTP?

    <p>Nucleoside diphosphate kinase.</p> Signup and view all the answers

    ATP has a stronger tendency to transfer its terminal phosphate group to water compared to glycerol-3-phosphate.

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

    Which of the following factors contribute to ATP's high phosphate group transfer potential?

    <p>Both electrostatic repulsion and resonance stabilization.</p> Signup and view all the answers

    PEP can generate ATP spontaneously.

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

    ATP can generate PEP spontaneously.

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

    Where does phosphocreatine have a significant role in the body?

    <p>Skeletal muscle.</p> Signup and view all the answers

    Phosphocreatine can spontaneously generate ATP.

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

    ATP can spontaneously generate phosphocreatine.

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

    Why is it important that ATP has an intermediate group-transfer potential?

    <p>The intermediate group-transfer potential allows ATP to act efficiently as a carrier of phosphoryl groups, driving both energy-requiring and energy-releasing reactions.</p> Signup and view all the answers

    There is an enzyme in cells that can directly transfer phosphate from a high-energy donor to a low-energy acceptor.

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

    ATP is formed from ADP and Pi when fuel molecules are oxidized.

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

    ATP is a long-term energy storage molecule in the body.

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

    Which of the following processes is NOT powered by ATP hydrolysis?

    <p>DNA replication</p> Signup and view all the answers

    Briefly describe oxidative phosphorylation in your own words.

    <p>Oxidative phosphorylation produces ATP by transferring electrons from NADH or FADH2 to oxygen through a series of protein complexes in the inner membrane of mitochondria. This process is coupled to the pumping of protons across the membrane, generating a proton gradient that drives ATP synthase to produce ATP.</p> Signup and view all the answers

    Which of the following molecules does NOT enter the mitochondria for oxidative phosphorylation?

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

    Describe the three stages of oxidative phosphorylation.

    <p>The three stages are 1) Acetyl-CoA production: Fueled by glucose, fatty acids, and amino acids, converting them to acetyl-CoA. 2) Acetyl-CoA oxidation: Acetyl-CoA enters the citric acid cycle where it is progressively oxidized, releasing electrons and protons. 3) Electron transport and oxidative phosphorylation: The electrons from stage 2 travel down the electron transport chain, and the energy released during their transfer is used to pump protons across the mitochondrial membrane. This proton gradient powers ATP synthesis.</p> Signup and view all the answers

    The flow of electrons in the electron transport chain pumps protons from the matrix to the intermembrane space.

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

    Which of the following complexes in the electron transport chain does NOT pump protons?

    <p>Complex II</p> Signup and view all the answers

    What are the mobile electron carriers within the mitochondrial electron transport chain?

    <p>Ubiquinone (Q) and cytochrome C.</p> Signup and view all the answers

    Ubiquinone (Q) transfers electrons from Complex II to Complex III.

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

    Which complex catalyzes the transfer of electron from cytochrome C to O2?

    <p>Complex IV</p> Signup and view all the answers

    Briefly describe the chemiosmotic hypothesis and its role in ATP synthesis.

    <p>The chemiosmotic hypothesis proposes that the energy released from electron transport in the mitochondrial membrane is used to pump protons from the matrix to the intermembrane space, creating a proton gradient. This gradient drives the flow of protons back across the membrane via ATP synthase, which harnesses the energy from this flow to synthesize ATP.</p> Signup and view all the answers

    The proton motive force is generated by a difference in proton concentration across the mitochondrial membrane.

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

    What is the role of ATP synthase in oxidative phosphorylation?

    <p>ATP synthase is the enzyme that uses the proton motive force, created by the electron transport chain, to generate ATP from ADP and Pi.</p> Signup and view all the answers

    The electron transport chain can be completely blocked by inhibitors, preventing both electron transport and ATP synthesis.

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

    How does oligomycin, a mitochondrial ATP synthase inhibitor, affect ATP synthesis and electron transport?

    <p>Oligomycin binds to ATP synthase, specifically the Fo component, blocking the flow of protons back into the matrix. This prevents ATP synthesis and, consequently, stops electron transport, as these two processes are closely coupled.</p> Signup and view all the answers

    The chemiosmotic hypothesis explains how oxidation and phosphorylation are coupled through the movement of protons across the mitochondrial membrane.

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

    What is the net ATP yield per molecule of NADH oxidized in oxidative phosphorylation?

    <p>3 ATP</p> Signup and view all the answers

    What is the net ATP yield per molecule of FADH2 oxidized in oxidative phosphorylation?

    <p>2 ATP</p> Signup and view all the answers

    The electron transport chain is composed of four protein complexes.

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

    Study Notes

    Biochemistry 2

    • Study of energy transduction in living cells and nature's chemical processes underlying these transductions.
    • Focuses on the initial and final energy states of reaction components, not the mechanisms or time needed for the reaction to occur.
    • Allows prediction of spontaneity of reactions and whether they will occur.

    Bioenergetics and Oxidative Phosphorylation

    • Objectives:
      • Understand general concepts of bioenergetics (enthalpy, entropy, free energy change, standard free energy).
      • Understand the mathematical relationship between these concepts.
      • Understand high-energy compounds (e.g., ATP).
      • Know the concept of oxidative phosphorylation and ATP production.

    Bioenergetics

    • Enthalpy, entropy, and free energy are key concepts.
    • Free energy change and standard free energy change are related to the equilibrium constant.
    • ATP is the universal energy carrier in biological systems.
    • Structural basis of high phosphate group transfer potential.
    • Phosphorylated compounds with high phosphate group transfer potential include PEP and phosphocreatine.
    • ATP has an intermediate group-transfer potential.

    Oxidative Phosphorylation

    • Electron carriers include NADH and FADH2.
    • Mitochondria are the respiratory organelles in cells.
    • NADH dehydrogenase has prosthetic groups FMN and iron-sulfur clusters.
    • QH2 (ubiquinone) is the entry for electrons from FADH2.
    • Cytochrome reductase facilitates electron transfer.
    • Cytochrome oxidase catalyzes the transfer of electrons from Cytochrome C to O2 (oxygen).
    • Chemiosmotic hypothesis explains ATP production.

    Bioenergetics & Thermodynamics

    • Systems tend toward lowest energy states (e.g., a fall, fatty acid oxidation).

    • Enthalpy (ΔH): change in heat content of reactants and products (ΔH = H₂(products) – H₁ (reactants)).

      • ΔH +ve = Endothermic (absorbs heat)
      • ΔH -ve = Exothermic (releases heat)

    • Entropy (ΔS): a measure of randomness/disorder.

      • ΔS +ve = Increased entropy
      • ΔS -ve = Decreased entropy

    • Neither enthalpy nor entropy alone can predict reaction direction

    Gibbs Free Energy

    • Gibbs free energy (ΔG) correlates enthalpy and entropy.

    • ΔG predicts reaction direction at specific concentrations.

    • ΔG = ΔH - TΔS where T = absolute temperature in Kelvin

    • Negative ΔG → spontaneous reaction (exergonic)

    • Positive ΔG → nonspontaneous reaction (endergonic)

    • Zero ΔG → equilibrium

    Standard Free Energy Change

    • Standard free energy change (ΔG°): free energy change under standard conditions (1 M concentration).

    • ΔG=AG° + RTln([B]/[A])

    • where [A] and [B] are the actual reactant & product concentrations.

    • Relation between equilibrium constant (Keq) and ∆G°:

    • ΔG° = -RTlnKeq

    • If Keq > 1, ΔG° < 0

    • If Keq = 1, ΔG° = 0

    • If Keq < 1, ΔG° > 0

    Equilibrium of Transamination Reactions

    • Most transamination reactions have constants near 1, enabling reactions in both degradation and biosynthesis.
    • Reaction direction depends on relative concentrations of reactants and products.

    Reaction of Glucose 6-PO4 into Fructose 6-PO4

    • Reaction under non-equilibrium, standard, and equilibrium conditions
    • Change in Gibbs free energy (ΔG):
      • Non-equilibrium: ΔG = −0.96 kcal/mol -Standard: ΔG = +0.4 kcal/mol -Equilibrium: ΔG = 0 kcal/mol

    What do you think is the right answer ?

    • Under standard conditions, the isomerization of glucose-6-phosphate to fructose-6-phosphate is endergonic (+0.4 kcal/mol), making the reaction unfavorable.
    • Maintaining a high concentration of glucose-6-phosphate will drive the reaction forward and make it more favorable.

    ATP-ADP Cycle

    • ATP is a continuously formed and consumed intermediate energy donor.
    • ATP hydrolysis is coupled with other reactions to favor product formation.

    Structural Basis of High P Group Transfer Potential of ATP

    • ATP has a stronger tendency to transfer its terminal phosphoryl group to water than glycerol-3-phosphate, indicating high phosphate transfer potential.
    • Reasons for high potential:
    • Electrostatic repulsion
    • Resonance stabilization

    Other Compounds with High Phosphate Group Transfer Potential

    • Phosphoenolpyruvate (PEP) and phosphocreatine have higher group transfer potential than that of ATP.
    • They can donate phosphate groups to ADP, driving ATP synthesis. (Important for energy storage and transfer in biological systems.

    Oxidative Phosphorylation

    • Process that generates most ATP from electron transfer to oxygen.
    • Results in pumping of protons across inner mitochondrial membrane.
    • Flow of protons drives ATP synthesis by ATP synthase.
    • Includes electron carriers (NADH and FADH2), and protein complexes (I, II, III, IV) in the electron transport chain.
    • Chemiosmosis/Proton Motive Force links electron transport and ATP synthesis, making ATP formation highly efficient.
    • Specific inhibitors (rotenone, antimycin A, CN/CO) block electron flow at specific complexes.

    The End

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