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Pharmacy is the health profession that links the health sciences with the chemical sciences and it is charged with ensuring the safe and effective use of pharmaceutical drugs. The word derives from the Greek: (pharmakon), meaning "drug" or "medicine". The scope of pharmacy practice includes more traditional roles such as compounding and dispensing medications, and it also includes more modern services related to health care, including clinical services, reviewing medications for safety and efficacy, and providing drug information. Pharmacists, therefore, are the experts on drug therapy and are the primary health professionals who optimize medication use to provide patients with positive health outcomes. An establishment in which pharmacy (in the first sense) is practiced is called a pharmacy, chemist's or drug store. In the United States and Canada, drug stores commonly sell not only medicines, but also miscellaneous items such as candy (sweets), cosmetics, and magazines, as well as light refreshments or groceries.

Thursday, May 3, 2012

Synthesis of Fatty Acids, Triacylglycerols, Eicosanoids, and the Major Membrane Lipids

  • Fatty acids are synthesized mainly in the liver, primarily from glucose.
  • Glucose is converted to pyruvate via glycolysis, which enters the mitochondrion and forms both acetyl coenzyme A and oxaloacetate, which then forms citrate.
  • The newly synthesized citrate is transported to the cytosol, where it is cleaved to form acetyl coenzyme A, which is the source of carbons for fatty acid biosynthesis.
  • Two enzymes, acetyl coenzyme A carboxylase (the key regulatory step) and fatty acid synthase, produce palmitic acid (16 carbons, no double bonds) from acetyl coenzyme A. After activation to palmitoyl coenzyme A, the fatty acid can be elongated or desaturated (adding double bonds) by enzymes in the endoplasmic reticulum.
  • The eicosanoids (prostaglandins, thromboxanes and leukotrienes) are potent regulators of cellular function and are derived from polyunsaturated fatty acids containing 20 carbon atoms.
  • Fatty acids are used to produce triacylglycerols (for energy storage) and glycerol phospholipids and sphingolipids (for structural components of cell membranes).
  • Liver-derived triacylglycerol is packaged with various apolipoproteins and secreted into the circulation as very low density lipoprotein.
  • As with dietary chylomicrons, lipoprotein lipase in the capillaries of adipose tissue, muscle, and the lactating mammary gland digests the triacylglycerol of very low density lipoprotein, forming fatty acids and glycerol.
  • Glycerophospholipids, synthesized from fatty acyl CoA and glycerol 3-phosphate, are all derived from phosphatidic acid. Various head groups are added to phosphatidic acid to form the mature glycerol phospholipids.
  • Phospholipid degradation is catalyzed by phospholipases.
  • Sphingolipids are synthesized from sphingosine, which is derived from palmitoyl coenzyme A and serine. Glycolipids, such as cerebrosides, globosides, and gangliosides, are sphingolipids.
  • The sole sphingosine-based phospholipid is sphingomyelin.
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