Cadena transportadora de electrones

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Figure 8.4 Mitochondrial structure and pathways of energy transduction: the mechanism of oxidative phosphorylation. Major fuels, such as pyruvate and fatty acids (FA), are transported into the matrix where they are oxidized to generate CO2 and the reduced nucleotide coenzymes NADH and FADH2. Oxidation of these nucleotides via the electron transport system reduces oxygen to water and pumps protonsby three proton pumps out of the matrix and into the intermembrane space (IMS), creating a pH gradient, which is the major contributor to the membrane potential. It should be noted that protons in the intermembrane space freely diffuse through the outer membrane via the protein porin, so the intermembrane space is roughly equivalent to the cytosol. Although the membrane potential is mostlycomprised of the proton gradient it actually consists of several electrochemical gradients and is expressed as a voltage. Controlled influx of protons through ATP synthase powers the synthesis of ATP by ATP synthase. Mitochondrial ATP is then exchanged for cytoplasmic ADP through the ADP-ATP translocase (T1). Phosphate (Pi), which is also required for ATP synthesis is transported by the phosphatetranslocase (T2). The inner membrane also contains uncoupling proteins (UCP) that may be used to allow the controlled leakage of protons back into the matrix. OMM, outer mitochondrial membrane; IMM, inner mitochondrial membrane; mtproteins, mitochondrial proteins; mtDNA, mitochondrial DNA; TOM and TIM, protein translocase complexes in outer and inner mitochondrial membrane; TCA, tricarboxylic acidcycle.

Downloaded from: StudentConsult (on 28 January 2010 06:59 AM) © 2005 Elsevier


Estados de salud yenfermedad men el ser humano • Termogénesis a bajas temperaturas • Estimular la síntesis de ATP durante estrés • Degradación de alimentos • Uso eficiente de nutrientes durante la inanición • Acoplamiento, síntesis de ATP y frecuencia respiratoria.

MITOCONDRIA ΔG Fosforilación oxidativa

• Transporte de electrones al oxígeno mediante generación de ATP. • “central eléctrica, fuente de ATPcelular”



Figure 8.1 Stages of fuel oxidation. NADH, reduced nicotinamide adenine dinucleotide; FADH2, reduced flavin adenine dinucleotide.

Downloaded from: StudentConsult (on 28 January 2010 06:59 AM) © 2005 Elsevier

• NADH + ½ O2 + H+ ΔG’o = -220 KJ/Mol ADP + Pi ATP + H2O ΔG’o = 30.5 KJ/Mol 220/30.5 = 7 moles de ATP/mol de NADH oxidado RENDIMIENTO REAL DE 3 moles deATP/mol NADH oxidado 2 moles de ATP/ mol de FADH2 NAD+ + H2O

• “Moneda energética” • Transductor principal de energía en seres vivos. • Se emplea para impulsar reacciones metabólicas que requieren energía. • Biosíntesis • Actividad muscular • Transporte celular • (mediante reacciones acopladas) • Requiere de ión magnesio

Figure 8.2Structures of high-energy phosphates. ATP is shown, together with its hydrolysis products, adenosine diphosphate (ADP) and adenosine monophosphate (AMP).

Downloaded from: StudentConsult (on 28 January 2010 06:59 AM) © 2005 Elsevier



Figure 8.3 The structure of redox coenzymes. NAD+ and its reduced form, NADH (nicotinamide adeninedinucleotide), consists of adenine, two ribose units, two phosphates, and nicotinamide; FAD and its reduced form, FADH2 (flavin adenine dinucleotide) consists of riboflavin, two phosphates, ribose and adenine; FMN and FMNH2 consist of riboflavin phosphate. The nicotinamide and riboflavin components of these coenzymes are reversibly oxidized and reduced during electron transfer (redox) reactions....
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