Step 1: Eicosanoid Basics:
Eicosanoids are signaling molecules formed from the oxidation of 20-carbon polyunsaturated fatty acids (PUFAs), especially arachidonic acid. The term "eicosanoid" originates from the Greek "eikosi," meaning twenty. These molecules act as local hormones, controlling processes like inflammation, fever, blood pressure, and blood clotting.
Step 2: Eicosanoid Breakdown:
Examine the options:
(A) Leukotrienes: Major eicosanoids produced mainly by leukocytes. They mediate inflammatory and allergic responses. Leukotrienes are generated from arachidonic acid through the lipoxygenase pathway.
(B) Prostaglandins: Another major class of eicosanoids found in nearly all human tissues. They have diverse hormone-like effects and are synthesized from arachidonic acid via the cyclooxygenase (COX) pathway.
(C) Lipoxins: Eicosanoids involved in resolving inflammation. They also originate from arachidonic acid.
(D) Cholesterol: A sterol, a lipid characterized by a four-ring steroid nucleus. It's a key part of animal cell membranes and a precursor for steroid hormones, but structurally and biosynthetically different from eicosanoids. It is not derived from a 20-carbon fatty acid.
Step 3: Conclusion:
Leukotrienes, prostaglandins, and lipoxins are all eicosanoids. Cholesterol is not. Thus, the correct selection is (A), (B), and (C).