MCAT Chemical and Physical Foundations of Biological Systems Flashcards: 5e Bioenergetics Biological Redox

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This deck focuses on 5e Bioenergetics Biological Redox, giving you a quick way to review the definitions, rules, and examples that matter most for MCAT Chemical and Physical Foundations of Biological Systems.

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Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: What happens to oxidation state when a species is oxidized?

Answer: Oxidation state increases. Loss of electrons results in a higher (more positive) oxidation number for the oxidized atom.

Flashcard 2: Which type of reaction has $\Delta G < 0$ and is thermodynamically spontaneous?

Answer: Exergonic reaction. Releases free energy, making the process favorable and able to occur without external input under standard conditions.

Flashcard 3: Which redox cofactor is the reduced form: $\text{NAD}^+$ or $\text{NADH}$?

Answer: $\text{NADH}$. Carries electrons gained during metabolic reductions, serving as an electron donor in the electron transport chain.

Flashcard 4: State the relationship between $\Delta G^\circ$, $R$, $T$, and the equilibrium constant $K$.

Answer: $\Delta G^\circ = -RT\ln K$. Links standard free energy to the equilibrium constant, indicating reaction favorability at equilibrium.

Flashcard 5: What is the condition for a spontaneous galvanic cell in terms of $E_{cell}$?

Answer: $E_{cell} > 0$. Positive cell potential indicates a spontaneous redox reaction driving electron flow.

Flashcard 6: Identify the direction of electron flow in a galvanic cell: anode to cathode or cathode to anode?

Answer: Anode to cathode. Electrons flow from the site of oxidation (anode) to the site of reduction (cathode) in spontaneous cells.

Flashcard 7: What happens to oxidation state when a species is reduced?

Answer: Oxidation state decreases. Gain of electrons results in a lower (more negative) oxidation number for the reduced atom.

Flashcard 8: Which process directly uses an $\text{H}^+$ gradient to synthesize ATP from ADP and $\text{P}_i$?

Answer: ATP synthase (chemiosmosis). Harnesses the proton motive force across the membrane to drive ATP production via oxidative phosphorylation.

Flashcard 9: State the relationship between $\Delta G$, $\Delta H$, $T$, and $\Delta S$.

Answer: $\Delta G = \Delta H - T\Delta S$. This equation determines the spontaneity of a reaction by balancing enthalpy, temperature, and entropy changes.

Flashcard 10: Which electrode is the site of oxidation in any electrochemical cell?

Answer: Anode. Oxidation, or loss of electrons, always occurs at this electrode in both galvanic and electrolytic cells.

Flashcard 11: What is the condition for equilibrium in terms of Gibbs free energy change?

Answer: $\Delta G = 0$. At equilibrium, the system has no net change in free energy, so forward and reverse rates are equal.

Flashcard 12: Which redox cofactor is the reduced form: $\text{FAD}$ or $\text{FADH}_2$?

Answer: $\text{FADH}_2$. Holds electrons from flavoprotein reductions, contributing to the proton gradient in mitochondrial respiration.

Flashcard 13: Identify the sign of $\Delta G^\circ$ when $K > 1$ for a reaction.

Answer: $\Delta G^\circ < 0$. When $K > 1$, products are favored at equilibrium, corresponding to a spontaneous reaction under standard conditions.

Flashcard 14: State the relationship between $\Delta G$, $\Delta G^\circ$, $R$, $T$, and $Q$.

Answer: $\Delta G = \Delta G^\circ + RT\ln Q$. This formula calculates free energy under non-standard conditions using the reaction quotient $Q$.

Flashcard 15: What is the definition of oxidation in terms of electron transfer?

Answer: Loss of electrons. Involves the transfer of electrons from a species, increasing its oxidation state.

Flashcard 16: Which agent is oxidized in a redox reaction: oxidizing agent or reducing agent?

Answer: Reducing agent. Donates electrons to another species, thereby undergoing oxidation itself in the process.

Flashcard 17: State the relationship between cell potential and free energy: $\Delta G$ and $E$.

Answer: $\Delta G = -nFE$. Relates the free energy change to the cell potential $E$ and the number of electrons transferred $n$, with Faraday's constant $F$.

Flashcard 18: Which agent is reduced in a redox reaction: oxidizing agent or reducing agent?

Answer: Oxidizing agent. Accepts electrons from another species, thereby undergoing reduction itself in the process.

Flashcard 19: For standard conditions, state the relationship between $E^\circ$, $n$, $F$, and $\Delta G^\circ$.

Answer: $\Delta G^\circ = -nFE^\circ$. Under standard conditions, this equation connects electrochemical potential to thermodynamic spontaneity.

Flashcard 20: State the formula for standard cell potential using standard reduction potentials.

Answer: $E^\circ_{cell} = E^\circ_{cathode} - E^\circ_{anode}$. Calculated by subtracting the anode's reduction potential from the cathode's to determine overall cell potential.

Flashcard 21: Which electrode is the site of reduction in any electrochemical cell?

Answer: Cathode. Reduction, or gain of electrons, always occurs at this electrode in both galvanic and electrolytic cells.

Flashcard 22: What is the definition of reduction in terms of electron transfer?

Answer: Gain of electrons. Involves the acceptance of electrons by a species, decreasing its oxidation state.

Flashcard 23: What is the sign of $\Delta G$ when $Q > K$ for a reaction at constant $T$?

Answer: $\Delta G > 0$. Indicates the reaction proceeds in the reverse direction toward equilibrium when products exceed reactants.

Flashcard 24: Which type of reaction has $\Delta G > 0$ and requires energy input to proceed?

Answer: Endergonic reaction. Absorbs free energy, rendering the reaction non-spontaneous and necessitating coupling to an exergonic process in biological systems.

Flashcard 25: What is the sign of $\Delta G$ when $Q < K$ for a reaction at constant $T$?

Answer: $\Delta G < 0$. Indicates the reaction proceeds spontaneously toward equilibrium when reactants are in excess relative to products.