Chapter 18. Oxidative Phosphorylation Flashcards
the energy inherent in the proton gradient established during the functioning of the respiratory chain; consists of a membrane potential as well as a chemical gradient.
Proton-motive force
A cytoplasmic complex that includes cytochrome c released from the mitochondria, which recruits and activates caspase 9, which in turn activates a cascade of caspases that result in programmed cell death (apoptosis).
Apoptosome
Molecular assembly of the inner mitochondrial membrane responsible for the respiratory-chain-driven synthesis of ATP. Also called Complex V, mitochondrial ATPase, H+-ATPase, or F0F1-ATPase.
ATP synthase (Complex V, F 1F 0 ATPase)
cysteine proteases that participate in the proteolytic cascade that occurs during apoptosis.
caspase
a transport protein that carries ADP into the mitochondria and ATP out in a coupled fashion.
ATP-ADP translocase (adenine nucleotide translocase, ANT)
the process in which ATP is formed as the result of the transfer of electrons from NADH or FADH2 to O2 via a series of electron carriers.
Oxidative phosphorylation
The generation of high-transfer-potential electrons by the citric acid cycle, their flow through the respiratory chain to O2, and the accompanying synthesis of ATP.
Cellular respiration
a mobile electron carrier that is a component of the respiratory chain; it shuttles between the oxidized ubiquinone form to the reduced ubiquinol form via a semiquinone intermediate; accepts electrons from NADH-Q reductase as well as succinate-Q reductase.
Coenzyme Q (Q, ubiquinone)
A measure of the tendency of chemical to accept electrons and thereby become reduced.
Reduction (redux, oxidation-reduction, Eā 0potential
a ubiquitous heme protein that catalyzes the dismutation of hydrogen peroxide into molecular oxygen and water.
Catalase
A large component of the respiratory chain that transfers electrons from NADH to ubiquinone and in the process pumps protons across the inner mitochondrial membrane to generate the proton-motive force. Also called NADH dehydrogenase or Complex I.
NADH-Q oxidoreductase (Complex I)
an integral membrane protein complex of the inner mitochondrial membrane that transfers electrons from the FADH2 formed in the citric acid cycle to coenzyme Q.
Succinate-Q reductase (Complex II)
A coenzyme for oxidation-reduction reactions derived from the vitamin riboflavin. The electron acceptor of FMN, the isoalloxazine ring, is identical with that of FAD, but FMN lacks the adenyl nucleotide component of FAD.
flavin mononucleotide (FMN)
the final complex of the respiratory chain, which transfers electrons from cytochrome c to molecular oxygen and concomitantly pumps protons across the inner mitochondrial membrane to generate the proton-motive force.
cytochrome c oxidase (complex IV)
an unusual 2Fe-2S center in that one of the iron ions is coordinated by two histidine residues rather than two cysteine residues.
Rieske center
a cascade of proteolytic enzymes that result in controlled cell death in response to significant cell damage or specific development programs.
Programmed cell death (apoptosis)
tight coupling or coordination of the oxidation of reduced cofactors (NADH, FADH2) in the electron transport chain and the phosphorylation of ADP to yield ATP in the mitochondrion; such control ensures that the rate of the citric acid cycle, where reduced cofactors are generated, corresponds to the demand for ATP.
Respiratory (acceptor) control
A component of the respiratory chain, this oxidoreductase carries electrons from coenzyme Q to cytochrome c and, in the process, pumps protons out of the mitochondrial matrix to generate the proton-motive force. Also called cytochrome reductase or Complex III.
Q-cytochrome c oxidoreductase (Complex III)
The population of coenzyme Q, reduced and oxidized, that exists in the inner mitochondrial membrane.
Q pool
The permeablization of the outer mitochondrial membrane, which occurs when mitochondria are damaged. The permeablization initiates the programmed cell death pathway (apoptosis).
Mitochondrial outer membrane permeabilization (MOMP)
a pathway that transfers electrons from cytoplasmic NADH into the mitochondria; dihydroxyacetone phosphate (DHAP) is reduced by NADH to glycerol 3-phosphate, which enters the mitochondria and is oxidized to yield FADH2and DHAP, which leaves the mitochondria.
Glycerol 3-phosphate shuttle
Proteins that contain clusters of iron and sulfur that play a role in electron transfer reactions; iron cycles between the Fe2+ and Fe3+ state. Also called nonheme iron proteins.
Iron-sulfur (nonheme iron) protein
a reversible shuttle, found in the liver and heart, used to transport electrons from cytoplasmic NADH to mitochondrial NAD.
Malate-aspartate shuttle
a set of reactions in which coenzyme Q cycles between the fully reduced state and the fully oxidized state via one-electron transfer reactions in which one of the electrons is temporarily stored in cytochrome b; provides a means of passing the two electrons of coenzyme Q to the single electron carrier cytochrome c, one electron at a time.
Q cycle
an enzyme that scavenges superoxide radicals by catalyzing the conversion of two of these radicals into hydrogen peroxide and molecular oxygen. Superoxide dismutase thus protects against damage by reactive oxygen species.
Superoxide dismutase
A mitochondrial membrane protein that plays a role in thermogenesis by forming a pathway for the flow of protons into the mitochondria, thereby generating heat without synthesizing ATP. Also called thermogenin.
Uncoupling protein (UCP)
The final complex of the respiratory chain, which transfers electrons from cytochrome c to molecular oxygen and concomitantly pumps protons across the inner mitochondrial membrane to generate the proton-motive force.
Cytochrome c (Cyt c)
