a (9Z,12E)-octadecadienoyl-containing glycerolipid + 2 Fe(III)-[cytochrome b5] + 2 H2O => a (9Z)-octadecenoyl-containing glycerolipid + 2 Fe(II)-[cytochrome b5] + O2 + 2 H(+)
a (9z,12e)-octadecadienoyl-containing glycerolipid + 2 fe(iii)-[cytochrome b5] + 2 h2o => a (9z)-octadecenoyl-containing glycerolipid + 2 fe(ii)-[cytochrome b5] + o2 + 2 h(+)