ETC and Oxidative Phosphorylation

Question 1

what is the significance of ETC and oxidative phosphorylation?

Answer 1

1. large energy requirements of cells
2. useful energy mobilized as ATP
3. most of energy from glycolysis, TCA and fatty acid oxidation
   -initially harvested as NADH and FADH2
   -converted to ATP via ETC and oxidative phosphorylation

Question 2

where does oxidative phosphorylation occur?

Answer 2

mitochondira
-outer membrane:permeable to low molecular weight molecules
-inner membrane: impermeable to small molecules and ions, highly involuted
-site of ETC and oxidative phosphorylation

Question 3

electron transport

Answer 3

stepwise transfer of electrons via series of redox reactions
-electrons are passed from NADH and FADH2, through carriers, ultimately to O2

Question 4

complex I

Answer 4

NADH dehydrogenase

Question 5

complex II

Answer 5

succinate dehydrogenase

Question 6

complex III

Answer 6

cytochrome reductase

Question 7

complex IV

Answer 7

cytochrome oxidase

Question 8

how do you determine the sequence of electron carriers?

Answer 8

1)redox potentials: “educated guesses”
2)spectral analysis and kinetics
-difference spectra: oxidized and reduced carriers absorb light differently->determine redox state
3)fractionation/purification of components
4)stage-specific inhibitors

Question 9

ETC and ATP production

Answer 9

-ATP synthesis requires transport of e- through the chain
-ETC and ATP production are coupled
-if no ADP present or ATP synthesis blocked->no e- transport and no reduction of O2
-respiration rate and ATP requirements are tightly regulated:respiratory control

Question 10

Chemiosmotic hypothesis

Answer 10

-electrochemical gradient of H+ generated during ETC provides the energy for ATP synthesis
-redox energy from ETC transport of H+ from matrix to IMS
-electrochemical potential (pH and charge gradient) is harvested to make ATP

Question 11

proton-motive force

Answer 11

energy to drive ATP synthesis is combinawtion of pH and charge difference across membrane

Question 12

what is evidence for the chemiosmotic theory?

Answer 12

1.inter membrane is impermeable to H+ and other ions
2.ETC causes H+ to be transported
3.elimination of pH gradient by uncouplers blocks ATP synthesis
4. artificial electrochemical gradient results in ATP synthesis

Question 13

uncouplers

Answer 13

cause electron transport in the absense of ATP synthesis
-oligomycin inhibits ATP synthase=no electron transport
-shuttle H+ across the inner membrane

Question 14

ATP synthase

Answer 14

-proton flux through ATP synthase drives ATP synthesis
-phosphate reacts directly with ADP in 1 step
-bound ATP made from ADP and Pi without proton motive force
-binding and conformational change makes ATP synthesis favorable