Aerobic Metabolism II: Electron Transport Chain and Oxidative Phosphorylation

Vocabulary practice flashcards covering complex components, inhibitors, phosphorylation theories, and shuttle mechanisms from the Electron Transport Chain lecture.

Electron Transport Chain (ETC)

A series of electron carriers that transfer the $e^-$ derived from reduced coenzymes to $O_2$, located in the inner mitochondrial membrane.

Complex I

Also known as NADH dehydrogenase; contains FMN and 7 Fe-S centers and catalyzes the transfer of electrons from NADH to Co Q (ubiquinone).

Complex II

Also known as Succinate dehydrogenase complex; it transfers electrons from succinate to Co Q via $FADH_2$.

Complex III

Ubiquinone-cytochrome c oxidoreductase; contains 2 b-type cytochromes, 1 cytochrome $c_1$, and 1 Fe-S center, transferring electrons from $UQH_2$ to cytochrome c.

Complex IV

Cytochrome oxidase; contains cyt a, cyt $a_3$, and 2 copper atoms ($Cu_A$ and $Cu_B$), delivering 4 $e^-$ and 4 protons to an $O_2$ molecule to form $2H_2O$.

Standard ATP Yield (NADH vs. FADH2)

$2.5$ ATP are synthesized for 1 pair of $e^-$ from NADH, while $1.5$ ATP are synthesized for 1 pair of $e^-$ from $FADH_2$.

Antimycin A

An electron transport inhibitor that blocks cyt b, causing $NAD^+$, flavins, and cyt b to become more reduced while cyt c, $c_1$, a, and $a_3$ become more oxidized.

Rotenone and Amytal

Inhibitors that specifically block NADH dehydrogenase (Complex I).

CO, Cyanide (CN-), and Azide (N3-)

Inhibitors that block cytochrome oxidase (Complex IV).

ATP Synthase (Complex V)

The site of oxidative phosphorylation consisting of the $F_1$ factor (active ATPase) and the $F_o$ factor (proton translocating protein).

F1 factor

The active ATPase component of Complex V made of 5 different subunits: $3\text{ }\text{α}$, $3\text{ }\text{β}$, $\text{γ}$, $\text{δ}$, and $\text{ε}$.

Fo factor

A proton translocating protein in ATP synthase consisting of 3 subunits: a, 2b, and 12c.

Proton Requirements for ATP Synthesis

Translocation of 3 protons through the complex is required for synthesis, while a 4th proton is used for transport of ATP, $OH^-$, ADP, and Pi.

Chemiosmotic coupling theory

The theory that electron transport generates a protonmotive force ($\text{Δ}p$) across the inner membrane, which drives ATP synthesis as protons return to the matrix via $F_o$.

P/O ratio

The number of Pi consumed per atom of oxygen reduced; reflects the degree of coupling between electron transport and ATP synthesis.

ATP-ADP translocator

A transport protein that mediates a 1:1 exchange of intramitochondrial ATP for cytoplasmic ADP.

Phosphate carrier

Transports $H_2PO_4^-$ into the mitochondrial matrix in exchange for $OH^-$.

Glycerol phosphate shuttle

Transfers electrons from cytosolic NADH to $FADH_2$ on the inner membrane; electrons enter the ETC at Complex II, yielding $1.5$ ATP per $FADH_2$.

Malate-aspartate shuttle

A more efficient shuttle where cytosolic OAA is converted to malate to enter the mitochondria, yielding $2.25$ ATP per NADH.