Question

Diagram the ETC and ATP synthase along a membrane (keep it simple, no fancy pictures, just basic shapes). Show the electron path through the ETC, and show what happens with ATP synthase (the reaction it catalyzes, and how it gets the energy for that reaction).

Answer 1

• ETC refers to electron transport chain. It is a process by which energy rich molecules like NADH2 and FADH2 are oxidized and the electrons hence generated are passed to oxygen through a series of electron carriers or transporters, resulting in the formation of water.
• It occurs in the inner membrane of mitochondria.
• There are four proteinaceous complexes or electron carriers embedded in the inner membrane of mitochondria, namely- complex-l, complex-ll, complex-lll and complex-lV. There is also an ATP synthase enzyme embedded in the inner membrane of mitochondria.
• NADH2  gets Oxidized at complex-l. The energy released is used to pump the protons into the intermembrane space. The electrons are passed on to a mobile electron carrier named, ubiquinone.
• FADH2 gets oxidized at complex-ll. The electrons are passed on to ubiquinone. But here, no protons are pumped.
• The ubiquinone delivers the electrons to complex-lll, which pumps protons into the intermembrane space.
• The electrons are delivered to another mobile electron carrier called Cytochrome- C or Cyt-C, which in turn delivers it to complex-lV.
• The complex-lV pumps protons into the intermembrane space. It passes the electrons to oxygen and reduces it to water.
• Due to high concentration of protons in the intermembrane space, a gradient called proton motive force is created across the mitochondrial membrane.
• The protons move down their concentration gradient, through the ATP synthase enzyme, into the mitochondrial matrix.
• The enzyme rotates and uses the energy from proton motive force to add an inorganic phosphate to ADP, resulting in the formation of ATP.