lec 15-Oxidative Phosphorylation Flashcards

Vocabulary-style flashcards covering the components, mechanisms, and regulation of oxidative phosphorylation based on the lecture material.

Oxidative Phosphorylation (OXPHOS)

The process where ATP synthesis is coupled to the transport of electrons from $NADH + H^+$ and $FADH_2$ through a series of protein complexes to oxygen.

Electron transport chain (ETC)

A series of protein complexes embedded in the mitochondrial inner membrane where electrons are transferred along carriers, finally reducing $O_2$ to create $H_2O$.

Prosthetic groups

Non-amino-acid structures tightly bound to proteins in the ETC that act as electron carriers, such as $FMN$, $FAD$, haem, and $Fe-S$ clusters.

Flavins ($FMN$ and $FAD$)

Flavin mononucleotide and Flavin adenine dinucleotide, which act as hydrogen acceptors and electron carriers within the electron transport chain.

Cytochromes

Proteins containing a haem group with an iron ion ($Fe^{2+}$ or $Fe^{3+}$) that carry electrons.

Iron-sulphur proteins ($Fe-S$ proteins)

Proteins containing $Fe-S$ clusters anchored via the side chain of cysteine residues that carry electrons on the $Fe^{2+}$ ions.

Ubiquinone ($Q$)

Also known as Coenzyme Q or CoQ; a non-protein-bound, freely mobile hydrogen acceptor in the inner mitochondrial membrane that transfers electrons from Complex I and Complex II to Complex III.

Redox potential ($E'_0$)

A measure of the electron affinity of a molecule; more negative values indicate a higher likelihood to pass on electrons, while more positive values indicate a higher likelihood to accept electrons.

Electrochemical gradient

A gradient created by pumping protons ($H^+$) from the mitochondrial matrix to the intermembrane space, resulting in both a concentration (pH) gradient and a voltage gradient (membrane potential).

Complex II

A complex in the ETC that does not pump protons because the difference in $E'_0$ between $FAD$ and $Q$ does not provide sufficient energy.

ATP synthase (Complex V)

A membrane-associated protein that uses the energy of the proton gradient to synthesize ATP from ADP and $P_i$.

F0 subunit

The part of ATP synthase embedded in the inner mitochondrial membrane that rotates as protons flow through it.

F1 subunit

The site of ATP synthesis in ATP synthase; it contains three sites that progress through O, L, and T states.

Stator

The stationary part of the ATP synthase rotary system that prevents the rotation of the F1 subunit.

Respiratory control

The regulation of the rate of electron transport by the levels of ADP and ATP; increased $[ADP]$ increases the rate of $O_2$ uptake, while increased $[ATP]$ decreases it.

Inhibitors (of ETC)

Substances such as $CN^-$, $CO$, or rotenone that reduce the transfer of electrons to or from complexes, thereby reducing ATP synthesis and potentially producing superoxide ($\bullet O_2^-$).

Uncouplers

Agents like dinitrophenol (DNP) or thermogenin that create channels in the inner mitochondrial membrane, making it permeable to protons and dissipating the proton gradient as heat.

ATP yield of 1 $NADH$

The reoxidation of one molecule of this carrier produces approximately $2.5$ ATP.

ATP yield of 1 $FADH_2$

The reoxidation of one molecule of this carrier produces approximately $1.5$ ATP.

Thermogenin

An uncoupling protein found in brown adipose tissue that dissipates the proton gradient to generate heat.

2,4-Dinitrophenol (DNP)

A toxic chemical and uncoupler once marketed as a 'slimming pill' that can cause death by dissipating the proton gradient, and is also classified as an explosive.