Biochemistry I - Lecture 25: Redox and Oxidative Phosphorylation

This set of vocabulary flashcards covers concepts from Biochemistry I Lecture 25, focusing on redox reactions, reduction potentials, the chemiosmotic hypothesis, and the mechanics of ATP synthase and mitochondrial shuttles.

Reduction

The gain of electrons by a chemical species.

Oxidation

The loss of electrons by a chemical species.

Reductant

A chemical species that acts as an electron donor and is oxidized during the reaction.

Oxidant

A chemical species that acts as an electron acceptor and is reduced during the reaction.

Standard Reduction Potential ($\mathcal{E}^\circ$)

A quantitative measure of the tendency of a chemical species to be oxidized or reduced under standard conditions ($1\,M$ solutions and $1\,atm$ pressure).

Faraday’s Constant ($\mathcal{F}$)

The electric charge on one mole of electrons, valued at $96.5\,kJ/V \cdot mol$ or $96.49\,kJ/V \cdot mol$.

Reference Half-Cell

A cell containing $1\,M\,H^+$ in equilibrium with $H_2$ gas at $1\,atm$ pressure, assigned an arbitrary standard reduction potential of $0.0\,V$.

$$\mathcal{E}^{\circ'}$$

The biochemical standard reduction potential measured at $pH = 7$. At this pH, the $H^+/H_2$ couple is $-0.42\,V$.

ΔGo' = -nℱΔƐo'

The equation used to calculate the biochemical standard free energy change for an oxidation-reduction reaction based on the change in reduction potential.

Mitchell or Chemiosmotic Hypothesis

The theory that an electrochemical proton gradient across the inner mitochondrial membrane drives the synthesis of ATP.

Proton-Motive Force

The electrochemical proton gradient resulting from an electrical potential ($\Delta \psi$) and a proton gradient ($\Delta pH$) across the inner membrane.

$F_1$ Subunit

The part of ATP synthase that encodes catalytic activity and consists of five polypeptides: $\alpha$, $\beta$, $\gamma$, $\delta$, and $\epsilon$.

$F_o$ Subunit

The hydrophobic component of ATP synthase that acts as a proton channel crossing the inner mitochondrial membrane, containing subunits $a$, $b$, and $c$.

OSCP (Oligomycin Sensitivity Conferring Protein)

A protein that connects the $F_o$ component in the membrane to the $F_1$ component both structurally and functionally.

ATP-ADP Translocase

A mitochondrial membrane protein that transports ATP out of the matrix and ADP into the matrix; each ATP transported out costs approximately $1\,H^+$.

Glycerol-3-phosphate Shuttle

An irreversible shuttle system, important in muscle, that delivers electrons from cytosolic NADH to the mitochondrial matrix using FAD.

Malate-aspartate Shuttle

The primary reversible shuttle in liver cells used to maintain the cytosolic supply of NAD+ and feed electrons into the electron transport chain.