The processes carried out by the electron transport chain are mediated by protein complexes (named Complexes I-V, DHO-QO, ETF-QO, and ANT). Complex I, or NADH : coenzyme Q oxidoreductase, uses the energy in NADH to pump protons into the intermembrane space of the mitochondrion, pumping 2 protons per electron and passing 2 electrons via coenzyme Q to complex III or coenzyme Q: cytochrome c oxidoreductase. Complex II or succinate : coenzyme Q oxidoreductase accepts energy from succinate produced in the citric acid cycle and passes it via coenzyme Q to complex III. Complex III pumps 1 protons per electron and passes 1 electron via cytochrome c to complex IV. Complex IV pumps 1 protons into the space between the mitochondrion’s two membranes before passing the electron to O2 which reacts to form water. Complex V (ATP synthase) is a rotary complex which allows approximately (determining the actual number is very difficult) 10 protons to enter the mitochondrial matrix along their concentration gradients. It uses the energy from the gradient to form the bond between ADP and the phosphate group to create ATP. The electron transfer flavoprotein : coenzyme Q oxidoreductase is also an electron-transporting molecule and is involved in the breakdown of fatty acids and amino acids. ANT (adenine nucleotide translocator) is also involved in oxidative phosphorylation as an energy carrying molecule. Each of these eight complexes plays a vital role in the health of the cell and any slight mutation in any one of the proteins that make up these complexes can lead to cell death or stress, which can both in turn lead to a number of diseases.
Tuesday, June 3, 2008
Membrane complexes
The processes carried out by the electron transport chain are mediated by protein complexes (named Complexes I-V, DHO-QO, ETF-QO, and ANT). Complex I, or NADH : coenzyme Q oxidoreductase, uses the energy in NADH to pump protons into the intermembrane space of the mitochondrion, pumping 2 protons per electron and passing 2 electrons via coenzyme Q to complex III or coenzyme Q: cytochrome c oxidoreductase. Complex II or succinate : coenzyme Q oxidoreductase accepts energy from succinate produced in the citric acid cycle and passes it via coenzyme Q to complex III. Complex III pumps 1 protons per electron and passes 1 electron via cytochrome c to complex IV. Complex IV pumps 1 protons into the space between the mitochondrion’s two membranes before passing the electron to O2 which reacts to form water. Complex V (ATP synthase) is a rotary complex which allows approximately (determining the actual number is very difficult) 10 protons to enter the mitochondrial matrix along their concentration gradients. It uses the energy from the gradient to form the bond between ADP and the phosphate group to create ATP. The electron transfer flavoprotein : coenzyme Q oxidoreductase is also an electron-transporting molecule and is involved in the breakdown of fatty acids and amino acids. ANT (adenine nucleotide translocator) is also involved in oxidative phosphorylation as an energy carrying molecule. Each of these eight complexes plays a vital role in the health of the cell and any slight mutation in any one of the proteins that make up these complexes can lead to cell death or stress, which can both in turn lead to a number of diseases.
