AP BIOLOGY

Detailed explanation-1: -The process accomplishes the pumping of four protons across the inner mitochondrial membrane to the intermembrane space . Complex II (Succinate-Q oxidoreductase).

Detailed explanation-2: -Complexes I and III each transfer four protons across the membrane per pair of electrons. In complex IV, two protons per pair of electrons are pumped across the membrane and another two protons per pair of electrons are combined with O2 to form H2O within the matrix.

Detailed explanation-3: -Complex I uses the energy released by the transfer of two electrons from NADH to ubiquinone to pump four protons across the bacterial plasma mem-brane or the inner mitochondrial membrane.

Detailed explanation-4: -Answer and Explanation: Two protons are pumped by FADH2. This is because FADH2 donates its electrons to complex II which does not pump protons. These electrons then flow to complexes III and IV which pump protons.

Detailed explanation-5: -Complex II does not pump protons directly. Complex II does send two protons on to Complex III in the form of the reduced ubiquinol.