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ELECTRON TRANSPORT CHAIN. NADH and FADH 2 , transfer their electrons to a series of compounds (mostly proteins), which are associated with the inner mitochondrial membrane .
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ELECTRON TRANSPORT CHAIN • NADH and FADH2, transfer their electrons to a series of compounds (mostly proteins), which are associated with the inner mitochondrial membrane. • The protein/complexes are arranged in order of increasing electronegativity (each successive compound wants the electrons more than the one before it). • The complexes/proteins (in order): NADH dehydrogenase, ubiquinone (UQ), succinate dehydrogenase, cytochrome complex, cytochrome c, cytochrome oxidase complex. • Each complex is reduced by gaining two electrons from the one before it and oxidized by donating its two electrons to the one after it. • As the electrons are passed they become more stable and therefore generate free energy. • This free energy is used to pump protons into the intermembrane space from the matrix (active transport). There are 3 proton pumps. • Oxygen is the final electron acceptor and it joins with two protons in the matrix to form water.
ELECTRON TRANSPORT CHAIN Steps: • NADH, from pyruvate oxidation and the Krebs Cycle, gives up its two electrons to NADH dehydrogenase, • The mobile carriers UQ and cytochrome c shuttle electrons from one protein complex to the next until they reach the cytochrome oxidase complex (final acceptor). • Each protein complex (3) also acts as a proton pump, using the free energy released to move protons from the matrix to the intermembrane space. • At the cytochrome oxidase complex, cytochrome oxidase, catalyzes the reaction between the electrons, protons and oxygen to form water. (2H+ + 1/2O2 --> H2O) • This process is highly exergonic (giving up free energy of 222kJ/mol). The chemical potential energy of the electron position is converted to the electrochemical potential energy of a proton gradient that forms across the inner mitochondrial membrane. • High concentration in the intermembrane space, low concentration in the matrix. • The proton gradient will be used to produced ATP.
ELECTRON TRANSPORT CHAIN • This process is highly exergonic (giving up free energy of 222kJ/mol). The chemical potential energy of the electron position is converted to the electrochemical potential energy of a proton gradient that forms across the inner mitochondrial membrane. • High concentration in the intermembrane space, low concentration in the matrix. • The proton gradient will be used to produced ATP.
ELECTRON TRANSPORT CHAIN • lFADH2 skips the first protein compound (starts at UQ). This means that NADH oxidation pumps three protons into the intermembrane space, while FADH2 oxidation pumps only two protons. • Three ATP are formed from NADH while two ATP are formed from FADH2.. • Once NADH and FADH2 are oxidized they pick up more H+ in glycolysis, pyruvate oxidation, or the Kreb's cycle (recycling of electron carriers). • There are many copies of the ETC along the cristae, therefore lots of ATP can be produced.
CHEMIOSMOSIS and OXIDATIVE ATP SYNTHESIS (Oxidative Phosphorylation) • There is an electrochemical gradient across the intermembrane space. (More protons outside than in the matrix). • Two parts: difference in charge and a difference in concentration. • The inner membrane is impermeable to protons. • The protons are forced through special proton channels that are coupled with ATP synthase (ATPase). • The electrochemical gradient produces a proton-motive force (PMF) that moves the protons through this ATPase complex. • Each time a proton comes through the ATPase complex, the free energy of the electrochemical gradient is reduced and this energy is used to create ATP from ADP + P in the matrix.
CHEMIOSMOSIS and OXIDATIVE ATP SYNTHESIS (Oxidative Phosphorylation) . • The continual production of ATP is dependent on the maintenance of a proton reservoir in the intermembrane space. • This depends on the continued movement of electrons and that depends on the availability of oxygen. • Therefore we need oxygen to prevent the ETC from being “clogged up” and we need food to provide the glucose that provides electrons for the ETC.
