Sphingomyelins on hydrolysis yield which of the following?
A) Glycerol, fatty acid, phosphoric acid, choline
B) Glycerol, sphingosine, fatty acid, choline
C) Sphingosine, fatty acid, phosphoric acid, choline ✔
D) Sphingosine, phosphoric acid, glycerol, inositol
E) Sphingosine, phosphoric acid, glycerol, serine
SPHINGOMYELIN = ceramide + phosphocholine. HYDROLYSIS by sphingomyelinase → SPHINGOSINE + FATTY ACID + PHOSPHORIC ACID + CHOLINE. Key: sphingomyelin has NO glycerol (unlike glycerophospholipids). The backbone is SPHINGOSINE (amino alcohol). Compare: lecithin (phosphatidylcholine) hydrolysis → glycerol + 2 fatty acids + phosphoric acid + choline. The presence of SPHINGOSINE (not glycerol) distinguishes sphingomyelin hydrolysis products from glycerophospholipid hydrolysis.
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A 25-year-old woman presents with muscle weakness, diagnosed with multiple sclerosis. Which of the following is under attack by the immune system?
A) Ceramide
B) Glycosphingolipid
C) Sphinganine
D) Sphingomyelin ✔
E) Sphingosine
MULTIPLE SCLEROSIS (MS) = autoimmune demyelination → immune cells (T cells, macrophages) attack the MYELIN SHEATH. The primary lipid target in myelin is SPHINGOMYELIN (the major phospholipid of myelin, together with galactocerebroside). The protein targets include MYELIN BASIC PROTEIN (MBP) and PROTEOLIPID PROTEIN (PLP). Progressive demyelination → impaired saltatory conduction → motor and sensory deficits. High-dose biotin (vitamin B7) used to promote remyelination in MS by activating acetyl-CoA carboxylase (fatty acid/myelin synthesis).
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In ganglioside nomenclature, the subscript 1 refers to which carbohydrate sequence attached to the ceramide?
A) Gal-GalNAc-Gal-Glc-ceramide ✔
B) Gal-Glc-ceramide
C) Gal-Glc-Glc-ceramide
D) GalNAc-Gal-Glc-ceramide
E) NANA-Gal-ceramide
GANGLIOSIDE SUBSCRIPT NUMBERING (carbohydrate chain length from ceramide): Subscript 1 = GalGalNAcGalGlc-ceramide (4 sugars: Gal-GalNAc-Gal-Glc, reading from outermost to ceramide). Subscript 2 = GalNAcGalGlc-ceramide (3 sugars). Subscript 3 = GalGlc-ceramide (2 sugars, lactosylceramide). GM1 = mono-sialosyl-4-sugar chain ganglioside. GM2 (Tay-Sachs substrate) = mono-sialosyl-3-sugar chain. GM3 = mono-sialosyl-2-sugar chain (simplest ganglioside).
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810 MCQs are arranged to the learning outcomes of this szabmu.