Question

Which of the following types of ion movement might be expected to require co-transport of protons from the intermembrane space to the matrix, since it could not be driven by the membrane potential across the inner membrane? (Assume that each ion being moved is moving against its concentration gradient.)

(a) import of Ca2+ into the matrix from the intermembrane space
(b) import of acetate ions into the matrix from the intermembrane space
(c) exchange of Fe2+ in the matrix for Fe3+ in the intermembrane space
(d) exchange of ATP from the matrix for ADP in the intermembrane space

Answer 1

The import of acetate ions into the matrix from the intermembrane space is likely to require co-transport of protons, due to the need to move against both the chemical and electrical gradients.

Step-by-step explanation:

The question asks which type of ion movement might require co-transport of protons (H+) from the intermembrane space to the matrix in a situation where the ion cannot be driven by the membrane potential. Among the options provided, the import of acetate ions from the intermembrane space into the matrix is the most likely to require co-transport of protons to move against its concentration gradient. This is because the membrane potential is mainly driven by the movement of protons down their electrochemical gradient, and a negative acetate ion would move against both the chemical gradient and the electrical gradient, which would necessitate an external energy source such as the proton gradient.