Describe how the electron transport chain is coupled to the synthesis of ATP in
ID: 163610 • Letter: D
Question
Describe how the electron transport chain is coupled to the synthesis of ATP in Mitochondria. An experiment was constructed to determine the electrochemical potential difference across the membrane of the mitochondria due to the translocation of protons across the membrane. A suspension of mitochondria was prepared and isolated. the total internal volume of the mitochondria was measured to be 0.002 cm^3 per Icm^3 of suspension. To 1.0 cm^3 of the mitochondria suspension was firstly incubated with valinomycin (to make the membrane permeable to ions) then incubated with 0.001 mole dm^-3 Rb^+. At equilibrium, the mitochondria were separated and the amount of Rb^+ was measured to be 1.988 times 10^-9 moles. Calculate the membrane potential of the mitochondria from the transfer of the Rb^+ across the membrane. the pH difference across the membrane of the mitochondria was measured to be 1.4 pH units with the outside acidic. Calculate the electrochemical potential difference across the membrane for a proton at 298K and identify the direction in which H^+ transport is favored.Explanation / Answer
Ans:
The electron transport chain(ETC)is coupled to synthesis of ATP in mitochondria:
1.The ETC and ATP synthesizing system are located on the inner mitichondrial membrane.There are five carriers that participate in ETC and arranged seqentially in a chain.Each of them can accept electrons and transfer them to following ones.
2.The energy releasd by ETC is used to create proton gradient across the mitochondrial inner membrane and that is uesd to drive ATP synthesis.
3.The actual synthesis of ATP is carried out by an enzyme called ATP synthase located in inner mitochondrial membrane.
4.The inner membrane of mitochondria is impermeable to protons.Energy of electrons is conserved in the form of differential distribution of protons across the membrane.As a result accumulation of proton in the intermembrane space,a difference in pH and voltage across the inner mitochondrial membrane is created.
5.The pumping out of the H+ ions generates higher concentration of H+ ions in the intermembrane space.Thus overall an electrochemical gadient its not formed.
6.The proton flow back into the mitochondrial matrix through ATP synthase and this drives ATP synthesis.
7.3 ATP are generated per NADH and 2ATP per FADH2 are believd to be produced.