Haemolysis caused by poisonous snake bite may be due to formation of which of the following?
A) Cardiolipin
B) Cephalin
C) Lysolecithin ✔
D) Phosphatidic acid
E) Sphingomyelin
SNAKE VENOM contains PHOSPHOLIPASE A2 → cleaves the FATTY ACID at C2 of PHOSPHATIDYLCHOLINE (lecithin) → LYSOLECITHIN (lyso-phosphatidylcholine) + free fatty acid. LYSOLECITHIN is a DETERGENT-LIKE molecule → inserts into RBC membrane → disrupts membrane integrity → HAEMOLYSIS. Also: phospholipase A2 cleaves phospholipids in tissue cell membranes → releases arachidonic acid → eicosanoid synthesis → inflammation. Phospholipase A2 also releases the substrate for platelet activating factor synthesis.
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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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334 MCQs are arranged to the learning outcomes of this rmu.