ESTRUCTURA DE LA MITOCONDRIA Y CADENA TRANSPORTADORA DE ELECTRONES

Fases de la respiración Celular

Localización de fases de respiración celular

Anatomía Bioquímica de la mitocondria

Qué es una mitocondria?

Estructura cilíndrica de 0.5 - 1 µm de diámetro.Además del núcleo, la mitocondria contiene su propio DNA y su propio mecanismo de replicación, transcripción y traducción. Cada mitocondria contiene de 2 a 10 copias de DNA

Membrana mitocondrial externa

Composición de las Membranas Mitocondriales

40% lípidos: (fosfolípidos) PC, colesterol en baja proporción60% proteínas

Espacio intermembrana

Membrana mitocondrial interna

20% lípidos: no colesterol; un 20% son cardiolípidos 80% proteínas: CTE, enzimas complementarios, transportadores específicos, ATP sintetasa

Matriz mitocondrial Enzimas del ciclo de Krebs y de la oxidación de AG grasos.2 a 10 moléculas de ADN circular, ARN y ribosomas (70S)Enzimas involucrados en la síntesis de proteínas, iones, nucleótidos, etc.

The intermembrane space contains cytochrome c as a mobile electron carrier for the respiratory chain. Release of cytochrome c into the cytosol initiates caspase enzyme activation.

Electron Carriers Function in Multienzyme Complexes

Transportadores Electrónicos: NAD+

Transportadores Electrónicos: FAD

Complejo I: FMN

Complejo II: FAD

Prosthetic groups of cytochromes

Iron-sulfur centers

Ubiquinone (Q, or coenzyme Q)

Complejos multiproteínicos enlazados a sus grupos prostéticos y asociados a sus transportadores móviles

NADH dehydrogenase (complex I) spans the membrane and has a proton pumping mechanism involving CoQ. The electrons go from CoQ to cytochrome b–c1 complex (complex III), and electron transfer does NOT involve complex II. Succinate dehydrogenase (complex II), glycerol 3-phosphate dehydrogenase, and ETF:Q oxidoreductase (shown in blue) all transfer electrons to CoQ, but do not span the membrane and do not have a proton pumping mechanism. As CoQ accepts protons from the matrix side, it is converted to QH2. Electrons are transferred from complex III to complex IV (cytochrome c oxidase) by cytochrome c, a small cytochrome in the intermembrane space that has reversible binding sites on the b–c1 complex and cytochrome c oxidase.

Summary of the flow of electrons and protons through the four complexes of the respiratory chain

NADH:ubiquinone oxidoreductase (Complex I)

Cytochrome bc1 complex (Complex III).

Path of electrons from NADH, succinate, fatty acyl–CoA, and glycerol 3-phosphate to ubiquinone.

The Q cycle.

Path of electrons through Complex IV.

Proton-motive force.

Transport of compounds across the inner and outer mitochondrial membranes

Mitochondrial ATP synthase complex.