AP BIOLOGY

Detailed explanation-1: -Answer and Explanation: The movement of protons (H+) down a concentration gradient through ATP synthase occurs from the inter-membrane space of the mitochondria (where protons accumulate) to the mitochondria matrix, passing through ATP synthase located on the mitochondria’s inner membrane.

Detailed explanation-2: -Energy is released in these “downhill” electron transfers, and several of the protein complexes use the released energy to pump protons from the mitochondrial matrix to the intermembrane space, forming a proton gradient. Image of the electron transport chain.

Detailed explanation-3: -During electron transport, energy is used to pump hydrogen ions across the mitochondrial inner membrane, from the matrix into the intermembrane space. A chemiosmotic gradient causes hy drogen ions to flow back across the mitochondrial membrane into the matrix, through ATP synthase, producing ATP.

Detailed explanation-4: -The ATP synthase (or F1F0 ATPase and also referred to as complex V) uses the free energy of an electrochemical gradient of protons (or sodium ions) generated by the respiratory chain to synthesize ATP.