Energy generation in mitochondria I. The overall scheme is known as the chemiosmotic mechanism: Two questions need to be answered: How does electron transport result in the expulsion of protons? How is the inward flow of protons used to drive ATP synthesis?. Refer to chapter 18, Stryer, 5e.
Refer to chapter 18, Stryer, 5e
Lecture 22, Michael Schweizer
Karp 3e, Figure 5.5
Electron Flow produces heat
All chemical energy from electron transfer converted to heat energy
Bio-wire is the respiratory assembly; electron flow produces ATP
Electron transfer from NADH to O2 involves multisubunit inner membranecomplexes I, III & IV, plusCoQ&cyt c. Within each complex, electrons pass sequentially through a series of carriers. Complex II exists attached to flavoprotein enzymes.
CoQ is located in the lipid core of the membrane, and there are CoQ binding sites in protein complexes.
Cytochrome c resides in the intermembrane space. It alternately binds to complex III or IV during e- transfer.
Proteins in cytoplasm or lumen or organelles are in solution and free-moving
Random orientation of reaction
Proteins in membranes are insoluble and fixed in orientation
Reactions can be directed
Substrates received and products formed vectorially
plasmamembrane of bacteria
inner mitochondrial membrane
2 mobile electron shuttles
Ubiquinone (co-enzyme Q) between I/II and III
Cytochrome c between III and IV
electrons (and H+) from NADH and FADH2 generated
at numerous oxydation steps