Electron Transport Chain & Oxidative Phosphorylation PDF

ELECTRON TRANSPORT CHAIN (ETC) AND OXIDATIVE PHOSPHORYLATION  Mitochondia The mitochondrion contained the enzymes responsible for electron transport and oxidative phosphorylation Energy rich molecules are metabolized to form CO2 and H2O; The metabolic intermediates of thes...

ELECTRON TRANSPORT CHAIN (ETC) AND OXIDATIVE PHOSPHORYLATION  Mitochondia The mitochondrion contained the enzymes responsible for electron transport and oxidative phosphorylation Energy rich molecules are metabolized to form CO2 and H2O; The metabolic intermediates of these reactions donate electrons to specific coenzymes – NAD+ and FAD to form energy rich reduced coenzymes – NADH and FADH2; This reduced coenzymes can donate a pair electrons to a set of electron carriers – electron transport chain; Electrons lose much of their free energy; This energy is captured and stored by the production of ATP from ADP and Pi; This process is called oxidative phosphorylation;  Electron Transport (Respiratory) Chain Electron transport chain (ETC) or respiratory chain (RC) functions to oxidize NADH and FADH that arise from different metabolic pathways carried out on nutrients, leading to release of energy (exergonic). The released E is used for the synthesis of ATP (oxidative phosphorylation).  Components Of The Electron Transport Chain: ------------------------------------------------------------------------------------ --------- The Four Electron Transport Complexes in the Inner Mitochondrial Membrane Respiratory Chain ------------------------------------------------------------------------------------ ---------- (a) Complex I NADH-CoQ reductase (ATP) (b) Complex II Succinate CoQ reductase (no ATP) (c) Complex III CoQ- Cytochrome C reductase, (ATP) (d) Complex IV Cytochrome C oxidase (ATP)  Cytochromes Cytochrome is protein that contains a bound heme; Each heme of cytochromes has a different reduction potential; The iron atoms in cytochromes are in Fe3+, as they accept electron, they are reduced to Fe2+, as they reoxidized to Fe3+ the electrons pass to the next component. Mechanism of Oxidative Phosphorylation 1- During the ETC (located at the inner mitochondrial membrane) , H+ are released into the intermembrane space (outside inner mitochondrial membrane). 2- The inner mitochondrial membrane is impermeable to H+, which accumulate outside the membrane. 3- An electrochemical gradient is creating across the membrane. An electrical gradient (with more positive charges on the outside of the membrane than on the inside) and chemical gradient or pH gradient (the outside of the membrane is at lower pH than the inside). 4- This H+ gradient (Proton Motif Force) is used by the ATP synthase complex to make ATP via oxidative phosphorylation. Electrochemical gradient: 1. Membrane Potential; 2. Proton Gradient; 3. Proton Motive Force; ATP synthase; Complex V ATP synthase has three conformations: L- loss T- tight O-open  Uncoupling proteins - UCP – create a “proton leak” – they allow proteins to reenter the matrix without energy being captured as ATP; UCP1 – thermogenin –heat production in brown adipocytes in mammals; Brown adipose tissue (BAT) is a unique thermogenic tissue in mammals that rapidly produces heat via nonshivering thermogenesis. Mammalian hibernators have evolved the greatest capacity for BAT. Aerobic Respiration: Total Energy Yield