Which statements about complex iv are true? 1) this complex catalyzes the reduction of oxygen to water. 2) despite consuming protons, this complex pumps h+ across the membrane at a rate of 4 per molecule of o2 reduced. 3) the protons flow across a gradient to the inner membrane space. 4) conformational changes as electrons flow through the complex alter the ability of some residues to bind protons. which statements about complex iv are true? 1) this complex catalyzes the reduction of oxygen to water. 2) despite consuming protons, this complex pumps h+ across the membrane at a rate of 4 per molecule of o2 reduced. 3) the protons flow across a gradient to the inner membrane space. 4) conformational changes as electrons flow through the complex alter the ability of some residues to bind protons. statements 1, 2, and 3 are correct. statements 1 and 4 are correct. statements 1, 2, and 4 are correct. statements 2, 3, and 4 are correct.