VPB 112: General Veterinary Biochemistry (1+1)

SIGNIFICANCE OF PHOSPHOLIPIDS

• They are important components of cell membranes.
• Phosphatidylcholine is the major lipid component of lung surfactant- the extracellular fluid layer lining the alveoli. Surfactant serves to decrease the surface tension of this fluid layer, thereby preventing alveolar collapse.
• Respiratory distress syndrome: It is also called as hyaline membrane disease. It is due to the lack of surfactant production in the lungs. The major component of lung surfactant is dipalmitoylphosphatidylcholine. When the concentration of surfactant decreases, surface tension on the lung alveoli increases a portion of the lung collapse, which reduces the exchange of oxygen and carbon dioxide.
• Sphingomyelin is an important constituent of the myelin of nerve fibers. Being a component of lipoprotein, they are involved in the transport of triacylglycerols, from liver and intestine to various tissues.
• Choline acts as a lipotrophic factor, prevents the accumulation of fats in liver.
• The detergent properties of phospholipids, especially phosphatidylcholine, play an important role in bile where they function to solubilize cholesterol.
• Phospholipids are involved in the process of blood coagulation.
• Arachidonic acid of phospholipids is the precursor for eicosanoids like prostaglandins, leukotrienes and thromboxanes.
• Hydrolysis of phosphatidylinositol produces a second messenger for the activity of hormones (diacylglycerol and inositol 1,4,5 triphosphate).
• Cardiolipin is a major lipid of mitochondrial membranes.