Lipids triacylglyceride/phospholipid

In the organism tissues, fatty acids are continually renewed in order to provide not only for the energy requirements, but also for the synthesis of multicomponent lipids (triacylglycerides, phospholipids, etc.). In the organism cells, fatty acids are resynthetized from simpler compounds through the aid of a supramolecular multienzyme complex referred to as fatty acid synthetase. At the Lynen laboratory, this synthetase was first isolated from yeast and then from the liver of birds and mammals. Since in mammals palmitic acid in this process is a major product, this multienzyme complex is also called palmitate synthetase. 

Compound lipids (phospholipids, sphingolipids, glycolipids, and cholesterol and its esters) that make part of the biomembrane are subject to a less active renew-al as compared with triacylglycerides. Their renewal is associated either with the restoration of an impaired portion of the membrane, or with the replacement of a defective molecule by a new one. 

As shown in Table IVA, the cells bind approximately 5% of the total radioactivity added 32% of this eictivity is associated with the cellular lipid fraction and 64% with the nonlipid (presumably protein) fraction. Of the lipid-associated activity, the distribution of I into cellular phospholipids, lysophosphatides, triacylglycerides, and free fatty acids is shown in Table IVB. The iodination reaction labels a variety of lipids of all classes without preference to charge, acid-base properties, or number of fatty acyl constituents, appears not to label intracellular lipids (e.g., cardiolipin, a major mitochondrial component), and labels lipids on both the exterior and interior hydrophilic surfaces of the plasma membrane (i.e., phosphatidylcholine and sphingomyelin as well as phosphatidyleth-anolamine and phosphatidylserine) (Table IVB). ... 

Enzyme-rich pancreatic juice which contains several enzymes capable of hydrolysing triacylglycerides and other lipids is secreted from the pancreas and mixed with the chyme. Pancreatic phospholipase Ag hydrolyzes phospholipid, thus producing fatty acids and lyso-phospholipids. Pancreatic triacylglyceride... 

Cholesterol and triacylglycerides (TAGs) are transported as complexes in the form of lipoprotein particles. These lipoprotein particles contain a core of TAGs and cholesteryl esters surrounded by a monolayer of phospholipids, cholesterol, and specific proteins called apoproteins. The apoproteins, specific to each type of lipoprotein, enable the hydrophobic lipids to be transported in the aqueous environment of the bloodstream. They also contain signals that target the lipoprotein particles to the cells or activate enzymes. The lipoprotein particles vary in density depending on the lipid/protein ratio and are named based on these densities. The higher the lipid/protein ratio, the lower the density of the particle. 

Lipids are the minor components of wheat grain (2-3%) and consist of polar and nonpolar components. Triacylglycerides (TAG) make up majority of the nonpolar lipids that are rich in unsaturated fatty acids. Huge variations in linoleic acid content of wheat, 45-75% of total fatty acids, were reported among five market classes of wheat (Davis et al., 1980). Polar lipids include glycolipids and phospholipids (Godon, 1994). 

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