<prompt> Lipid soluble plasma membrane associated antioxidant -UbiquitinVitamin EVitamin CGlutathione  <response>: Ans. is b i.e., Vitamin EAlpha-tocopherol is the only lipid soluble, chainbreaking antioxidant present in biological membranes.o The main function of vitamin E is as a chain-breaking, free radical-trapping antioxidant in cell membranes and plasma lipoproteins by reacting with lipid peroxide radicals formed by peroxidation of polyunsatured fatty acid.Antioxidant systemsA Non-enzymatic systemi Lipid soluble membrane associated antioxidants: Vitamin E tocopheral is most important, - carotene.ii Water soluble reductants : Glutathione, vitamin C ascorbate.iii Tissue proteins: Transferrin, ferritin, lactoferrin, ceruloplasmin.B Enzymatic system It includes catalase, superoxide dismutase SOD and glutathione peroxidase. 