A 7-month-old girl exhibits an exaggerated startle response, has decreased muscle tone, and demonstrates a loss of hearing. Previously attained developmental milestones appear to be disappearingin this infant. Physical and biochemical examinations show cherry-red spots on the retinas of both eyes and a significant reduction in hexosaminidase A activity. A diagnosis of Tay-Sachs disease is made. Which of the following properties of the lipid substrate for the deficient enzyme is the most likely cause of these symptoms?

Question

Quizplus · Accepted Answer

The symptoms of Tay-Sachs disease are caused by the accumulation of GM2 gangliosides in cells due to the deficiency of the enzyme hexosaminidase A, which is responsible for breaking down these lipids.  Tay-Sachs disease is a member of a family of disorders identified as the GM2 gangliosidoses. The G M2 gangliosidotic diseases are severe psychomotor developmental disorders caused by the inability to properly degrade membrane-associated gangliosides of the GM2 family which then accumulate within the lysosomes of cells. Because neural cell membranes are enriched in G M2 gangliosides, the inability to degrade this class of sphingolipid results in neural cell death.

A 7-Month-Old Girl Exhibits an Exaggerated Startle Response, Has Decreased