Question

Electron Transport Chain (ETC) proteins

A) actively pump protons from the matrix into the intermembrane space

B) actively pump protons from the intermembrane space into the matrix

C) passively transport protons from the matrix into the intermembrane space

D) passively transport protons from the intermembrane space into the matrix

E) ETC proteins synthesise ATP

Answer 1

Electron transport chain (ETC) proteins- C.) Passively transport protons from matrix into the intermembrane space.

In ETC of inner mitochondrial membrane, electrons are transferred from NADH (in case of complex 1) or FADH2 ( in case of complex 2) through a series of electron transport carriers finally to Oxygen (in complex 4), which gets reduced to H₂O. Concomitantly, protons passively pass through these complexes from matrix to inter membrane space. This generates a proton motive force, which helps in ATP synthesis via ATP synthase complex present on the inner mitochondrial membrane.

In ETC, each successive complex has high electronegativity than previous complex, which means electron transport carriers are arranged in the order of low electronegativity to high electronegativity.