Chapter 6 Objectives

Terms in this set (15)

The four complexes accept or donate electrons to the mobile electron carrier coenzyme Q and cytochrome c. Each carrier in the ETC can receive electrons to the next acceptor in the chain. The electrons combine with O2 and H+ to form H20. This requirement for O2 makes the electron transport process the respiratory chain, which accounts for the greatest portion of the body's use of O2. Coenzyme Q (a lipid soluble quinone) and cytochrome C shuttles electrons between complexes. Cytochrome C is looseley associated with the the outer face of inner membrane; like CoQ cytochrome C is a mobile electron carrier. Electrons ultimately combine with O2 and H+ which makes water. Water is a requirement for cellular respiration (greatest oxygen demand by the body). NADH formation: NAD+ is reduced to NADH by dehydrogenases that remove two hydrogens atoms from their substrate. Both electrons but only one H+ is transferred to NAD+ forming NADH plus a free H+. NADH dehydrognase: The free H+ plus the hydride ion carried by NADH are transferred to NADH dehydrogenase which is embedded in protein complex 1. Complex 1 is a tightly bound molecule of flavin mononucleotide, a coenzyme stucturally related to FAD that accepts the two hydrogen aroms becoming FMNH2. NADH dehydrogenase contains peptide subunits with Fe-S centers. At Complex 1, electrons move from NADH to FMN to the iron of the Fe-S centers and then to CoQ. As electrons flow, they lose energy. This energy is used to pump four H+ across the inner mitochondrial membrane, from the matrix to the intermembrane space. Succinate dehydrogenase: At complex II, electrons from the succinate dehydrognase catalyzed oxidation of succinate to fumarate move from the coenzyme, FADH2, to an Fe-S protein, and then to CoQ.