Phospholipid abundance

Sphingomyelins are the second major group of phospholipids. These compounds have sphingosine or a related dihydroxyamine as their backbone and are particularly abundant in brain and nerve tissue, where they are a major constituent of the coating around nerve fibers. 

Phosphoacylglycerols containing choline (Figure 14-8) are the most abundant phospholipids of the cell mem-... 

Phosphatidylcholine, commonly known as lecithin, is the most commonly occurring in natnre and consists of two fatty add moieties in each molecule. Phosphati-dylethanolamine, also known as cephahn, consists of an amine gronp that can be methylated to form other compounds. This is also one of the abundant phospholipids of animal, plant, and microbial origin. Phosphatidylserine, which has weakly acidic properties and is found in the brain tissues of mammals, is found in small amounts in microorganisms. Recent health claims indicate that phosphatidylserine can be used as a brain food for early Alzheimer s disease patients and for patients with cognitive dysfunctions. Lysophospholipids consist of only one fatty acid moiety attached either to sn-1 or sn-2 position in each molecule, and some of them are quite soluble in water. Lysophosphatidylchohne, lysophosphatidylserine, and lysophos-phatidylethanolamine are found in animal tissues in trace amounts, and they are mainly hydrolytic products of phospholipids. 

This process probably occurs in vivo because the adduct of ethanolamine and p-hydroxyphe-nylacetaldehyde is abundant in the phospholipids of LDL exposed to activated neutrophils and tyrosine. 

The rate of production of DAG in the cell does not occur linearly with time, but rather it is biphasic. The first peak is rapid and transient and coincides with the formation of IP3 and the release of Ca2+ this DAG is therefore derived from the PI-PLC catalyzed hydrolysis of phosphatidylinositols [1]. There is then an extended period of enhanced DAG production that is now known to be derived from the more abundant phospholipid phosphatidylcholine (PC), which has a different composition of fatty acid side chains [9]. Although DAG may be generated directly from PC through the action of PC-PLC, it can also be formed indirectly from PC. In this pathway, PC is first hydrolyzed by PLD to give choline and phosphatidic acid, which is then converted to DAG by the action of a phos-phatidic acid phosphatase [10,11 ]. 

Eicosatetraenoic Arachidonic C20 4 (n = 6) Abundant in animal phospholipids, marine algae and fish... 

Docosapentaenoic Elupadonic C22 5 (n = 3) Abundant in fish, minor in animal phospholipids... 

As shown in Table 1, the acyl moiety of cardiolipin is comprised almost entirely of unsaturated fatty acids. Other membrane phospholipids such as phosphatidyl choline and phosphatidyl ethanolamine contain 1(M0 mol of saturatedfatty acids such as palmitic acid (Ci6 0) and stearic acid (Ci8 0) per 100 mol of total fatty acids. In particular,linoleic acid (Cl8 2) is the most abundant polyunsaturated fatty acid consisting of 80 mol%, linolenic acid (Cl8 3) 8 mol%, and oleic acid (Ci8 i) 6 mol%. Therefore, by using a commercially available cardiolipin purified from bovine heart mitochondria, we characterized auto-oxidation products by reverse phase HPTLC and reverse phase HPLC. 

Another major component of the cell membranes are the lipopolysaccharides, which are present as phospholipid bilayers. Following the death of bacteria, the biopolymers that constitute their cell walls and membranes become part of the detrital organic carbon pool. The great abundance of these biopolymers in seawater and the sediments is a reflection of their resistance to chemical degradation and the important role that bacterioplankton play in marine biomass production. 

For pure phosphatidylcholine bilayers, the orientation of the headgroup has been well characterized showing that headgroups are aligned approximately parallel to the bilayer surface. Because only one phosphorus with 100% natural abundance is contained in the phospholipid molecule, NMR has become an important tool to study the phospholipid headgroup structure and dynamics. ... 

Phospholipids containing phosphatidyl, inositol, lecithin, serine, and ethanolamine (Stevenson 1986) are the second most abundant identifiable form of organic P in the upper layer of the subsurface. These groups contain glycerol, fatty acids, and phosphate (Sims and Pierzjinski 2005). The P in the structure is a diester, which is more susceptible to degradation in soils than monoesters. 

Phosphatidylcholine (lecithin) is the most abundant phospholipid in membranes. Phosphatidylethanolamine (cephalin) has an ethanolamine residue instead of choline, and phosphatidylserine has a serine residue. In phosphatidylinositol, phosphatidate is esterified with the sugarlike cyclic polyalcohol myo-inositol. A doubly phosphorylated derivative of this phospholipid, phosphatidylinositol 4,5-bisphosphate, is a special component of membranes, which, by enzymatic cleavage, can give rise to two second messengers, diacylglycerol (DAG) and inositol l,4,5trisphosphate (InsPsi see p.386). 

Lyotropic liquid-crystalline nanostructures are abundant in living systems. Accordingly, lyotropic LC have been of much interest in such fields as biomimetic chemistry. In fact, biological membranes and cell membranes are a form of LC. Their constituent rod-like molecules (e.g., phospholipids) are organized perpendicularly to the membrane surface yet, the membrane is fluid and elastic. The constituent molecules can flow in plane quite easily but tend not to leave the membrane, and can flip from one side of the membrane to the other with some difficulty. These LC membrane phases can also host important proteins such as receptors freely floating inside, or partly outside, the membrane. 

Component of phospholipids of membranes of the body s cells, and is abundant in the brain and muscles Necessary for the repair and growth of skeletal muscle tissue... 

Incorporation of different fatty acids into lipids depends on the relative abundance of their CoA derivatives and their acyl-transferase )< , values. The synthetic enzymes which form membrane phospholipids may select the acid by molecular features not in accord with the optimal physiological properties of the products (110), resulting in the formation of membranes which do not function adequately. 

PC and PE are the most abundant phospholipids in most eukaryotic cells. The primary route of their synthesis uses choline and ethanolamine obtained either from the diet or from the turnover of the body s phospholipids. [Note In the liver, PC also can be synthesized from phosphatidylserine (PS) and PE (see below).]... 

Many other phospholipids are present in small amounts or in a limited number of species. These include phosphonolipids, which contain a C-P bond and are abundant in ciliate protozoa such as Tetrahymena and in some other invertebrates.26 Phosphonoethyl-amine replaces phosphoethanolamine in these lipids. A consequence of this structural alteration is a high... 

Glycolipids are important constituents of the plasma membranes, of the endoplasmic reticulum, and of chloroplasts. The cerebrosides and their sulfate esters, the sulfatides, are especially abundant in myelin. In plant membranes, the predominant lipids are the galactosyl diglycerides.29 74 The previously described ether phospholipids (archaebacteria), ceramide arnino-ethylphosphonate (invertebrates), and sulfolipid (chloroplasts) are also important membrane components. 

Phosphorus. Eightv-tive percent of the phosphorus, the second most abundant element in the human body, is located in bones and teeth. Whereas there is constant exchange of calcium and phosphorus between bones and blood, there is very little turnover in teeth. The Ca P ratio In hones is constant at about 2 1. Every tissue and cell conlains phosphorus, generally as a sail nr ester of mono-, di-. or tribasic phosphoric acid, as phospholipids, or as phosphorylaled sugars. Phosphorus is involved in a large number and wide variety of metabolic functions. Examples arc carbohydrate metabolism, adenosine triphosphate (ATP) from fatty acid metabolism, and oxidative phosphorylation. 

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