This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Which of the following occurs in the lipidosis known as Tay-Sachs disease? 
Select and explain. 
A. Synthesis of a specific ganglioside is excessive, B. Xanthomas due to cholesterol deposition are observed, C. Phosphoglycerides accumulate in the brain, D. Ganglioside GM2 is not catabolized by lysosomal enzymes
D: Ganglioside GM2 is not catabolized by lysosomal enzymes
Answer: D: Ganglioside GM2 is not catabolized by lysosomal enzymes 
Explanation: In the genetic disorder known as Tay-Sachs disease, ganglioside GM2 is not catabolized. As a consequence, the ganglioside concentration is elevated many times higher than normal. The functionally absent lysosomal enzyme is b-N- acetylhexosaminidase. The elevated GM2 results in irreversible brain damage to infants, who usually die before the age of 3 years. Under normal conditions, this enzyme cleaves N- acetylgalactosamine from the oligosaccharide chain of this complex sphingolipid, allowing fuher catabolism to occur. The cause of most lipidoses (lipid storage diseases) is similar. That is, a defect in catabolism of gangliosides causes abnormal accumulation. None of the other choices result in lipidotic disorders. Ref: Hopkin R., Grabowski G.A. (2012). Chapter 361. Lysosomal Storage Diseases. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e.