In a mitochondrion, if the matrix atp concentration is high, and the intermembrane space proton concentration is too low to generate sufficient proton-motive force, then a) atp synthase will increase the rate of atp synthesis. b) atp synthase will stop working. c) atp synthase will hydrolyze atp and pump protons into the intermembrane space. d) atp synthase will hydrolyze atp and pump protons into the matrix.

ATP synthase will hydrolyze ATP and pump protons into the intermembrane space.

Explanation:

Under normal conditions, the intermembrane space of mitochondria has higher proton ion concentration than the matrix. The inner mitochondrial membrane is impermeable to protons. The concentration gradient drives pass movement of protons through proton channels and the energy is used to drive the synthesis of ATP. The synthesized ATP molecules are released in the matrix.

If the matrix has higher ATP concentration and the proton concentration in intermembrane space is low, ATP synthase would use the energy of hydrolysis of ATP to pump protons from matrix towards intermembrane space. These conditions would not support ATP synthesis.