Chapter 3: Lipids of Biological Significance

Chapter 3: Lipids of Biological Significance

An adult man suffered from stable angina pectoris for 15 years, during which time there was progressive heart failure and repeated pulmonary thromboembolism. On his death at age 63, autopsy disclosed enormous cardiomyopathy (1100 g), cardiac storage of globotriaosylceramide (11 mg lipid/g wet weight), and restricted cardiocytes. To which of the following lipid classes does globotriaosylceramide belong?

A. glycosphingolipid

B. phospholipid

C. saturated fatty acid

D. sphingomyelin

E. triglyceride

Answer A: This man was afflicted with Fabry disease, a disorder characterized by the lysosomal accumulation of glycosphingolipids with terminal α-galactosyl residues.

The parents of an 18-month-old girl are alarmed at the rapid deterioration in her motor skills and the appearance of an engorged belly. They note that when their daughter tries to follow the movement of an object she thrusts her head in the direction of movement as if she cannot move her eyes from side-to-side. Physical and laboratory examination reveals hepatosplenomegaly, skeletal lesions, dry scaly skin, and lipid-laden foam cells that have the appearance of wrinkled paper when viewed under a microscope. Given the observed symptoms in this patient, which of the following is the most likely class of lipid to be found at elevated levels within the lipid-laden foam cells?

A. ganglioside

B. omega fatty acid

C. phospholipid

D. sphingomyelin

E. triglyceride

Answer A: This individual is suffering from Gaucher disease, characterized by the lysosomal accumulation of glucosylceramide (glucocerebroside) which is a normal intermediate in the catabolism of globosides and gangliosides.

You are studying a cell line derived from a liver tumor. This cell line expresses a mutated form of glycerol kinase. Which of the following lipid classes is most likely to be found at reduced levels in this cell line due to this gene defect?

A. cholesterol

B. fatty acids

C. phospholipids

D. sphingolipids

E. triglycerides

Answer E: Triglycerides are composed of a backbone of glycerol to which 3 fatty acids are esterified. One of the pathways to triglyceride synthesis in hepatocytes is initiated by the phosphorylation of glycerol via the action of glycerol kinase. Therefore, a defect in glycerol kinase activity in these cells would ...