NADH + 5 Proton + Ubiquinone → NAD⁺ + Ubiquinol + 4 Proton (intermembrane space)

Complex I · NADH:ubiquinone oxidoreductase EC 7.1.1.2

Collects the two electrons from NADH and passes them to ubiquinone. With the energy that jump releases it pumps four protons from the matrix into the intermembrane space, against their gradient. It is the first of the three pumps.

exergonic
irreversible
Inner mitochondrial membrane

in depth

ΔG°′: −70.4 kJ/mol
Location: Inner mitochondrial membrane

Fun fact

It is the largest complex in the inner membrane: some forty-five subunits and a chain of eight to nine iron-sulfur clusters that conduct the electrons along almost ninety ångströms.