a (5Z,9Z,12Z,15Z)-octadecatetraenoyl-containing glycerolipid + 2 Fe(III)-[cytochrome b5] + 2 H2O => (9Z,12Z,15Z)-octadecatrienoyl-containing glycerolipid + 2 Fe(II)-[cytochrome b5] + O2 + 2 H(+)
a (5z,9z,12z,15z)-octadecatetraenoyl-containing glycerolipid + 2 fe(iii)-[cytochrome b5] + 2 h2o => (9z,12z,15z)-octadecatrienoyl-containing glycerolipid + 2 fe(ii)-[cytochrome b5] + o2 + 2 h(+)
a (5Z,9Z,12Z,15Z)-octadecatetraenoyl-containing glycerolipid + 2 Fe(III)-[cytochrome b5] + 2 H2O => (9Z,12Z,15Z)-octadecatrienoyl-containing glycerolipid + 2 Fe(II)-[cytochrome b5] + O2 + 2 H(+)
a (5z,9z,12z,15z)-octadecatetraenoyl-containing glycerolipid + 2 fe(iii)-[cytochrome b5] + 2 h2o => (9z,12z,15z)-octadecatrienoyl-containing glycerolipid + 2 fe(ii)-[cytochrome b5] + o2 + 2 h(+)