AP BIOLOGY

Detailed explanation-1: -The energy used in the electron transport chain pumps protons across the inner mitochondrial membrane from the inner matrix to the intermembrane space, producing a strong hydrogen concentration gradient. This process was called chemiosmosis by its discover, Peter Mitchell.

Detailed explanation-2: -The respiratory chain pumps H+ out of the matrix to create a transmembrane electrochemical proton (H+) gradient, which includes contributions from both a membrane potential and a pH difference.

Detailed explanation-3: -When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the intermembrane space, the result is the creation of proton-motive force (d is correct). The proton-motive force describes the force created by the tendency of hydrogen ions to move down their concentration gradient.

Detailed explanation-4: -During electron transport, the participating protein complexes push protons from the matrix out to the intermembrane space. This creates a concentration gradient of protons that another protein complex, called ATP synthase, uses to power synthesis of the energy carrier molecule ATP (Figure 2).