Question

Draw the following molecule: 1-steric, 2-lenoleoyl(18:2Δ9,12) phosphatidylcholine

Draw platelet-activating factor

Draw sphingomyelin with an N-palmitoyl substitution

What is the physiological relevance of each lipid you have drawn above?

Describe two similarities that all three lipids share.

Answer 1

•1-steric, 2-linoleoyl(18:2Δ9,12) phosphatidylcholinePhysiological relevance

The stearic acid moiety is derived from animal fats, coco butter and sesame oil, while the linoleic acid moiety is derived from seed oils. Phospholipids, are ubiquitous in nature and are key components of the lipid bilayer of cells, as well as being involved in metabolism and signaling. While most phospholipids have a saturated fatty acid on C-1 and an unsaturated fatty acid on C-2 of the glycerol backbone, the fatty acid distribution at the C-1 and C-2 positions of glycerol within phospholipids is continually in flux, owing to phospholipid degradation and the continuous phospholipid remodeling that occurs while these molecules are in membranes. PCs can be synthesized via three different routes. In one route, choline is activated first by phosphorylation and then by coupling to CDP prior to attachment to phosphatidic acid. PCs can also synthesized by the addition of choline to CDP-activated 1, 2-diacylglycerol. A third route to PC synthesis involves the conversion of either PS or PE to PC.

•platelet-activating factorPhysiological relevance

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PAF is used to transmit signals between neighboring cells and acts as a hormone, cytokines, and other signaling molecules. The PAF signaling system can trigger inflammatory and thrombotic cascades, amplify these cascades when acting with other mediators, and mediate molecular and cellular interactions (cross talk) between inflammation and thrombosis. Unregulated PAF signaling can cause pathological inflammation and has been found to be a cause in sepsis, shock, and traumatic injury. PAF can be used as a local signaling molecule and travel over very short distances or it can be circulated throughout the body and act via endocrine.

•sphingomyelin with an N-palmitoyl substitution

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Physiological relevance

Sphingolipids, a family of membrane lipids, are bioactive molecules that participate in diverse functions controlling fundamental cellular processes such as cell division, differentiation, and cell death. Given that most of these cellular processes form the basis for several pathologies, it is not surprising that sphingolipids are key players in several pathological processes. This review discusses the role of the sphingolipid metabolic pathway in diabetes, Alzheimer’s disease, and hepatocellular carcinoma, with a special emphasis on the changes in gene expression pattern in these disease conditions. For convenience, the sphingolipid metabolic pathway is divided into hypothetical compartments (modules) with each compartment representing a physiological process and changes in gene expression pattern are mapped to each of these modules. It appears that alterations in the gene expression pattern in these disease conditions are biased to manipulate the system in order to result in a particular disease.