oxidative phosphorylation Flashcards
oxidative phosphorylation
-harvest ATP from the oxidation of NADH and FADH2 using O2
-occuris in the mitochondrial inner membranes
-electrons from NADH and FADH2 are transferred to O2 (oxidation)
-the electron transfer is couple with transfer of proton across membrane, generating PMF
complex 1
-NADH ubiquinone oxidoreductase
-electron transder from NADH to ubiquinone
-major source of ROS that damages mitochondrial DNA and causes aging
-inhibited by rotenone
complex 2
-succinate dehydrogenase
-electron transfer from succinate to ubiquinone
-part of TCA cycle
-no proton transfer
-some other enzymes also pass electrons to ubiquinone via FADH2
complex 3
-cytochrome bc1 complex (membrane bound protein complex of 500 kDa)
-electron transfer from ubiquinone to cytochrome c
cytochromes
-proteins that contain heme groups
-iron in heme is alternately oxidized or reduces
-mammalian mitochondria have 3 types of cytochromes
complex 4
-cytochrome c oxidase
-cytochrome c is mobile electron carrier
electron transfer from cytochrome c to O2
-inhibited by cyanide (CN-), azide (N3-), and carbon monoxide (CO) (bind to iron in heme of cytochrome c oxidase)
F1F0-ATP synthase
-located in the inner mitochondrial membrane
-synthesizes ATP using the proton gradient
- the active site is in the B-subunit; the three B subunits have different conformations, which are necessary for ATP synthesis
_______ through the F0 subunit causes rotation of F1, which results in conformational chances in the B subuntis
movement of protons
conformational changes in the B subunits cause the synthesis and release of
ATP
uncouplers
-uncouple oxidation and ATP synthesis
-dissipate the protein gradients by shuttling protons across the inner mitochondrial membrane
-oxygen is consumed without ATP synthesis
-energy is lost as heat
UCP-1
-uncoupling protein
-expressed in brown adipose tissues, which play a major role in nonshivering thermogenesis, especially in newborns
-located in the inner mitochodrial membrane
-dissipates the proton gradient
reactive oxygen species
-cytochrome c oxidase catalyzes the reduction of O2 to water by passing one electron at a time without releasing the intermediates
-intermediates are highly reactive and can cause cellular damages
-small number of reactive oxygen species are formed from the leakage i the electron transport chain
-immune cells produce reactive oxygen species using NADPH oxidase to kill bacteria
cellular defenses against reactive oxygen species
-superoxide dismutase and catalase
-glutathione peroxidase
-antioxidants
superoxide dismutase and catalase
-primary defense mechanism
glutathione peroxidase
-uses glutathione as a reductant
-oxidized glutathione is reduced by glutathione reductase using NADPH