Bioenergetics and Biological Oxidation–Reduction (5E) - MCAT Chemical and Physical Foundations of Biological Systems
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State the relationship between cell potential and free energy: $\Delta G$ and $E$.
State the relationship between cell potential and free energy: $\Delta G$ and $E$.
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$\Delta G = -nFE$. Relates the free energy change to the cell potential $E$ and the number of electrons transferred $n$, with Faraday's constant $F$.
$\Delta G = -nFE$. Relates the free energy change to the cell potential $E$ and the number of electrons transferred $n$, with Faraday's constant $F$.
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What is the condition for a spontaneous galvanic cell in terms of $E_{cell}$?
What is the condition for a spontaneous galvanic cell in terms of $E_{cell}$?
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$E_{cell} > 0$. Positive cell potential indicates a spontaneous redox reaction driving electron flow.
$E_{cell} > 0$. Positive cell potential indicates a spontaneous redox reaction driving electron flow.
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State the formula for standard cell potential using standard reduction potentials.
State the formula for standard cell potential using standard reduction potentials.
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$E^\circ_{cell} = E^\circ_{cathode} - E^\circ_{anode}$. Calculated by subtracting the anode's reduction potential from the cathode's to determine overall cell potential.
$E^\circ_{cell} = E^\circ_{cathode} - E^\circ_{anode}$. Calculated by subtracting the anode's reduction potential from the cathode's to determine overall cell potential.
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Identify the direction of electron flow in a galvanic cell: anode to cathode or cathode to anode?
Identify the direction of electron flow in a galvanic cell: anode to cathode or cathode to anode?
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Anode to cathode. Electrons flow from the site of oxidation (anode) to the site of reduction (cathode) in spontaneous cells.
Anode to cathode. Electrons flow from the site of oxidation (anode) to the site of reduction (cathode) in spontaneous cells.
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Which electrode is the site of oxidation in any electrochemical cell?
Which electrode is the site of oxidation in any electrochemical cell?
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Anode. Oxidation, or loss of electrons, always occurs at this electrode in both galvanic and electrolytic cells.
Anode. Oxidation, or loss of electrons, always occurs at this electrode in both galvanic and electrolytic cells.
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Which electrode is the site of reduction in any electrochemical cell?
Which electrode is the site of reduction in any electrochemical cell?
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Cathode. Reduction, or gain of electrons, always occurs at this electrode in both galvanic and electrolytic cells.
Cathode. Reduction, or gain of electrons, always occurs at this electrode in both galvanic and electrolytic cells.
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Which redox cofactor is the reduced form: $\text{NAD}^+$ or $\text{NADH}$?
Which redox cofactor is the reduced form: $\text{NAD}^+$ or $\text{NADH}$?
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$\text{NADH}$. Carries electrons gained during metabolic reductions, serving as an electron donor in the electron transport chain.
$\text{NADH}$. Carries electrons gained during metabolic reductions, serving as an electron donor in the electron transport chain.
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Which redox cofactor is the reduced form: $\text{FAD}$ or $\text{FADH}_2$?
Which redox cofactor is the reduced form: $\text{FAD}$ or $\text{FADH}_2$?
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$\text{FADH}_2$. Holds electrons from flavoprotein reductions, contributing to the proton gradient in mitochondrial respiration.
$\text{FADH}_2$. Holds electrons from flavoprotein reductions, contributing to the proton gradient in mitochondrial respiration.
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Which process directly uses an $\text{H}^+$ gradient to synthesize ATP from ADP and $\text{P}_i$?
Which process directly uses an $\text{H}^+$ gradient to synthesize ATP from ADP and $\text{P}_i$?
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ATP synthase (chemiosmosis). Harnesses the proton motive force across the membrane to drive ATP production via oxidative phosphorylation.
ATP synthase (chemiosmosis). Harnesses the proton motive force across the membrane to drive ATP production via oxidative phosphorylation.
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Which type of reaction has $\Delta G < 0$ and is thermodynamically spontaneous?
Which type of reaction has $\Delta G < 0$ and is thermodynamically spontaneous?
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Exergonic reaction. Releases free energy, making the process favorable and able to occur without external input under standard conditions.
Exergonic reaction. Releases free energy, making the process favorable and able to occur without external input under standard conditions.
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Which type of reaction has $\Delta G > 0$ and requires energy input to proceed?
Which type of reaction has $\Delta G > 0$ and requires energy input to proceed?
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Endergonic reaction. Absorbs free energy, rendering the reaction non-spontaneous and necessitating coupling to an exergonic process in biological systems.
Endergonic reaction. Absorbs free energy, rendering the reaction non-spontaneous and necessitating coupling to an exergonic process in biological systems.
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State the relationship between $\Delta G$, $\Delta H$, $T$, and $\Delta S$.
State the relationship between $\Delta G$, $\Delta H$, $T$, and $\Delta S$.
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$\Delta G = \Delta H - T\Delta S$. This equation determines the spontaneity of a reaction by balancing enthalpy, temperature, and entropy changes.
$\Delta G = \Delta H - T\Delta S$. This equation determines the spontaneity of a reaction by balancing enthalpy, temperature, and entropy changes.
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What is the condition for equilibrium in terms of Gibbs free energy change?
What is the condition for equilibrium in terms of Gibbs free energy change?
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$\Delta G = 0$. At equilibrium, the system has no net change in free energy, so forward and reverse rates are equal.
$\Delta G = 0$. At equilibrium, the system has no net change in free energy, so forward and reverse rates are equal.
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State the relationship between $\Delta G$, $\Delta G^\circ$, $R$, $T$, and $Q$.
State the relationship between $\Delta G$, $\Delta G^\circ$, $R$, $T$, and $Q$.
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$\Delta G = \Delta G^\circ + RT\ln Q$. This formula calculates free energy under non-standard conditions using the reaction quotient $Q$.
$\Delta G = \Delta G^\circ + RT\ln Q$. This formula calculates free energy under non-standard conditions using the reaction quotient $Q$.
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State the relationship between $\Delta G^\circ$, $R$, $T$, and the equilibrium constant $K$.
State the relationship between $\Delta G^\circ$, $R$, $T$, and the equilibrium constant $K$.
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$\Delta G^\circ = -RT\ln K$. Links standard free energy to the equilibrium constant, indicating reaction favorability at equilibrium.
$\Delta G^\circ = -RT\ln K$. Links standard free energy to the equilibrium constant, indicating reaction favorability at equilibrium.
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Identify the sign of $\Delta G^\circ$ when $K > 1$ for a reaction.
Identify the sign of $\Delta G^\circ$ when $K > 1$ for a reaction.
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$\Delta G^\circ < 0$. When $K > 1$, products are favored at equilibrium, corresponding to a spontaneous reaction under standard conditions.
$\Delta G^\circ < 0$. When $K > 1$, products are favored at equilibrium, corresponding to a spontaneous reaction under standard conditions.
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What is the sign of $\Delta G$ when $Q < K$ for a reaction at constant $T$?
What is the sign of $\Delta G$ when $Q < K$ for a reaction at constant $T$?
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$\Delta G < 0$. Indicates the reaction proceeds spontaneously toward equilibrium when reactants are in excess relative to products.
$\Delta G < 0$. Indicates the reaction proceeds spontaneously toward equilibrium when reactants are in excess relative to products.
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What is the sign of $\Delta G$ when $Q > K$ for a reaction at constant $T$?
What is the sign of $\Delta G$ when $Q > K$ for a reaction at constant $T$?
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$\Delta G > 0$. Indicates the reaction proceeds in the reverse direction toward equilibrium when products exceed reactants.
$\Delta G > 0$. Indicates the reaction proceeds in the reverse direction toward equilibrium when products exceed reactants.
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What is the definition of oxidation in terms of electron transfer?
What is the definition of oxidation in terms of electron transfer?
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Loss of electrons. Involves the transfer of electrons from a species, increasing its oxidation state.
Loss of electrons. Involves the transfer of electrons from a species, increasing its oxidation state.
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What is the definition of reduction in terms of electron transfer?
What is the definition of reduction in terms of electron transfer?
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Gain of electrons. Involves the acceptance of electrons by a species, decreasing its oxidation state.
Gain of electrons. Involves the acceptance of electrons by a species, decreasing its oxidation state.
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Which agent is oxidized in a redox reaction: oxidizing agent or reducing agent?
Which agent is oxidized in a redox reaction: oxidizing agent or reducing agent?
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Reducing agent. Donates electrons to another species, thereby undergoing oxidation itself in the process.
Reducing agent. Donates electrons to another species, thereby undergoing oxidation itself in the process.
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Which agent is reduced in a redox reaction: oxidizing agent or reducing agent?
Which agent is reduced in a redox reaction: oxidizing agent or reducing agent?
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Oxidizing agent. Accepts electrons from another species, thereby undergoing reduction itself in the process.
Oxidizing agent. Accepts electrons from another species, thereby undergoing reduction itself in the process.
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What happens to oxidation state when a species is oxidized?
What happens to oxidation state when a species is oxidized?
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Oxidation state increases. Loss of electrons results in a higher (more positive) oxidation number for the oxidized atom.
Oxidation state increases. Loss of electrons results in a higher (more positive) oxidation number for the oxidized atom.
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What happens to oxidation state when a species is reduced?
What happens to oxidation state when a species is reduced?
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Oxidation state decreases. Gain of electrons results in a lower (more negative) oxidation number for the reduced atom.
Oxidation state decreases. Gain of electrons results in a lower (more negative) oxidation number for the reduced atom.
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For standard conditions, state the relationship between $E^\circ$, $n$, $F$, and $\Delta G^\circ$.
For standard conditions, state the relationship between $E^\circ$, $n$, $F$, and $\Delta G^\circ$.
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$\Delta G^\circ = -nFE^\circ$. Under standard conditions, this equation connects electrochemical potential to thermodynamic spontaneity.
$\Delta G^\circ = -nFE^\circ$. Under standard conditions, this equation connects electrochemical potential to thermodynamic spontaneity.
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