Question 1

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

glycosphingolipid

Accepted Answer

Globotriaosylceramide is a type of glycosphingolipid, which is a class of lipids that includes glycosylated derivatives of ceramide.  This man was afflicted with Fabry disease, a disorder characterized by the lysosomal accumulation of glycosphingolipids with terminal a-galactosyl residues.

Question 2

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

ganglioside

Accepted Answer

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.

Question 3

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

triglycerides

Accepted Answer

Glycerol kinase is involved in the metabolism of glycerol to glycerol-3-phosphate, a precursor for triglyceride synthesis. A mutation in glycerol kinase would likely reduce the levels of triglycerides.  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 result in reduced capacity to synthesize triglycerides

Question 4

You are doing experiments in cell culture with a novel inhibitor, of lipid metabolism. Your studies determine that in the presence of the inhibitor, the cells are unable to elicit a normal response to antigen addition to the culture. Which of the following lipid classes is likely to be reduced because of the addition of the inhibitor?

A) cholesterol
B) plasmalogen
C) phospholipids
D) sphingolipids
E) triglycerides

Accepted Answer

Sphingolipids are important components of cell membranes and play a crucial role in cell signaling and immune responses. Inhibition of lipid metabolism affecting sphingolipids could impair the cell's ability to respond to antigens.  Platelet-activating factor (PAF) functions as a mediator of hypersensitivity, acute inflammatory reactions, and anaphylactic shock. PAF is a member of the plasmalogen family of lipid. PAF is synthesized in response to the formation of antigen-IgE complexes on the surfaces of basophils, neutrophils, eosinophils, macrophages, and monocytes. The inhibitor is most likely inhibiting the synthesis of PAF in these cells thus, the lack of appropriate response to antigen addition.

Question 5

Hypersensitive individuals have IgE to specific antigens (eg, pollen, bee venom) on the surface of their leukocytes (monocytes, macrophages, basophils, eosinophils). When these individuals are challenged with antigen, the antigen-IgE complexes induce synthesis and release of which of the
Following physiologically potent lipids?

A) arachidonic acid
B) leukotriene B₄
C) platelet-activating factor (PAF)
D) prostaglandin E₂
E) thromboxane A₂(TXA₂)

Accepted Answer

PAF is released from basophils and other leukocytes upon activation by antigen-IgE complexes.

Question 6

The omega-3 class of polyunsaturated fatty acids (PUFAs) has potent effects on cardiovascular function. The most active omega-3 PUFAs are docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). These PUFAs are precursors for which of the following biologically active lipids?

A) gangliosides
B) leukotrienes
C) prostaglandins
D) resolvins
E) thromboxanes

Accepted Answer

Resolvins are biologically active lipids derived from omega-3 PUFAs, specifically DHA and EPA, and play a role in resolving inflammation.  The resolvins are a class of lipid involved in the resolution of inflammatory responses, hence the derivation of their names. The D class resolvins are synthesized from DHA and the E class resolvins are derived from EPA.

Deck 3: Lipids of Biological Significance