Lipids, Steroids & Eicosanoids – Key Vocabulary

Comprehensive vocabulary list covering sphingolipids, lipid storage diseases, steroids, fat-soluble vitamins, eicosanoid biosynthesis, and pharmacological inhibitors relevant to the lecture notes.

Sphingolipid

Class of membrane lipids built on a sphingosine backbone; includes ceramides, sphingomyelins and glycosphingolipids.

Ceramide

Simplest sphingolipid made of sphingosine + fatty acid via amide bond; forms skin barrier and participates in signaling.

Sphingomyelin

Ceramide plus phosphocholine or phosphoethanolamine on C-1; abundant in myelin and plasma membranes.

Glycosphingolipid

Ceramide with one or more sugar residues linked β-glycosidically; includes cerebrosides and gangliosides.

Cerebroside

Glycosphingolipid containing a single sugar (glucose or galactose) on ceramide.

Ganglioside

Complex glycosphingolipid with oligosaccharide head and ≥1 sialic acid; key for neurogenesis and synapse formation.

Inositol-containing ceramide

Ceramide whose head group is an inositol residue; found in some fungi and plants.

Sphingosine

18-carbon amino alcohol backbone of sphingolipids; can act as signaling molecule when phosphorylated.

Sphingosine-1-phosphate

Phosphorylated sphingosine functioning as potent second messenger that guides lymphocyte egress.

Myelin

Lipid-rich sheath (high in sphingomyelin) insulating axons to speed nerve impulse conduction.

Hexosaminidase A

Lysosomal enzyme whose deficiency causes Tay-Sachs disease via GM₂ ganglioside buildup.

Tay-Sachs disease

Autosomal-recessive GM₂ gangliosidosis marked by neurodegeneration and blindness from hexosaminidase A deficiency.

Alpha-galactosidase A

Enzyme lacking in Fabry disease, causing globotriaosylceramide accumulation.

Fabry disease

X-linked lipid storage disorder with pain, skin lesions, kidney & heart failure due to α-galactosidase A deficiency.

Ceramidase

Enzyme that removes fatty acid from ceramide; deficiency leads to Farber disease.

Farber disease

Disorder with lipid buildup in joints & nervous tissue caused by ceramidase deficiency.

Glucocerebrosidase

Enzyme deficient in Gaucher disease; normally degrades glucocerebroside.

Gaucher disease

Most common sphingolipidosis; causes hepatosplenomegaly & bone lesions from glucocerebroside storage.

Sphingomyelinase

Enzyme lacking in some Niemann-Pick types; hydrolyzes sphingomyelin to ceramide.

Niemann-Pick disease

Group of disorders with sphingomyelin or cholesterol accumulation in RES organs; often fatal in childhood.

Steroid

Non-saponifiable lipid with fused tetracyclic (cyclopentanoperhydrophenanthrene) ring system derived from isoprene.

Isoprene unit

Five-carbon building block (C₅H₈) used to synthesize terpenes and steroids.

Cholesterol

Principal animal sterol; precursor for steroid hormones, bile acids and vitamin D.

Stigmasterol

Plant sterol analogous to cholesterol.

β-Sitosterol

Common plant sterol structurally similar to cholesterol.

Ergosterol

Fungal sterol produced by yeasts; target of many antifungal drugs.

Bile acid

Polar cholesterol derivative (e.g., cholic acid) that emulsifies dietary fats in intestine.

Progesterone

Steroid hormone regulating menstrual cycle and pregnancy; precursor for corticosteroids.

Testosterone

Primary male sex hormone, an androgen synthesized from cholesterol.

Estradiol

Potent estrogen steroid controlling female reproductive system.

Cortisone

Glucocorticoid steroid with anti-inflammatory properties.

Norethindrone

Synthetic progestin used in oral contraceptives.

Vitamin D

Secosteroid derived from cholesterol; regulates calcium & phosphate homeostasis.

Vitamin A

Terpene-derived fat-soluble vitamin essential for vision and epithelial integrity.

Vitamin E

Tocopherol antioxidant composed of aromatic ring + long terpene tail.

Vitamin K

Fat-soluble vitamin required for γ-carboxylation of clotting factors.

Eicosanoid

C₂₀ arachidonic-acid–derived local hormone including prostaglandins, thromboxanes, leukotrienes & lipoxins.

Arachidonic acid

20:4 ω-6 fatty acid released by phospholipase A₂; precursor to eicosanoids.

Prostaglandin

Cyclooxygenase product (prostanoid) influencing inflammation, vasomotor tone and reproduction.

Prostacyclin (PGI₂)

Vascular endothelium prostaglandin that inhibits platelet aggregation and vasodilates.

Thromboxane A₂

Platelet-derived eicosanoid promoting aggregation and vasoconstriction.

PGE₂

Prostaglandin causing vasodilation, fever and pain; produced mainly by COX-2.

PGF₂α

Prostaglandin that contracts uterine and bronchial smooth muscle.

Cyclooxygenase (COX)

Enzyme converting arachidonic acid to PGG₂/PGH₂; exists as constitutive COX-1 and inducible COX-2.

PGH₂

Central prostaglandin endoperoxide intermediate converted to various prostanoids.

5-Lipoxygenase (5-LOX)

Enzyme producing leukotriene precursors from arachidonic acid.

Leukotriene

LOX-derived eicosanoid mediating asthma, inflammation and hypersensitivity.

LTB₄

Leukotriene chemotactic for neutrophils; promotes adhesion and degranulation.

LTC₄ / LTD₄ / LTE₄

Cysteinyl leukotrienes constituting slow-reacting substance of anaphylaxis; powerful bronchoconstrictors.

Slow-reacting substance of anaphylaxis (SRS-A)

Mixture of LTC₄, LTD₄ & LTE₄ causing severe bronchoconstriction during anaphylaxis.

Lipoxin

Anti-inflammatory eicosanoid that opposes leukotrienes and promotes resolution.

Phospholipase A₂

Enzyme liberating arachidonic acid from membrane phospholipids; abundant in snake venom.

NSAID

Non-steroidal anti-inflammatory drug (e.g., ibuprofen) that reversibly inhibits COX enzymes.

Aspirin

Acetylating NSAID that irreversibly inhibits COX by acetylating Ser 529/516; reduces pain, fever, clotting.

Montelukast

Leukotriene receptor antagonist used to treat asthma.

Zileuton

5-Lipoxygenase inhibitor preventing leukotriene synthesis; asthma prophylaxis.

FLAP (5-LOX-activating protein)

Membrane protein that facilitates 5-LOX interaction with arachidonic acid.