Phosphoglycerides membrane structure

In addition to phosphoglycerides, membranes from animal cells usually contain a second group of phospholipids, the sphingolipids. Sphingomyelin, which is representative of this group, has the structure... 

Cell membrane structural components. Phosphoglycerides, sphingolipids, and steroids make up the basic structure of all cell membranes. These membranes control the flow of molecules into and out of cells and allow cell-to-cell communication. 

According to the fluid-mosaic model of membrane structure ( ), cell membranes consist of a fluid phospholipid bilayer. Embedded within this bilayer are globular proteins essential to membrane function. A large class of phospholipids present in membranes are phosphoglycerides (1 ). The fatty acid in the number 2 position is often unsaturated ( ). In plants, the unsaturated fatty acid is frequently linolenic acid (1 ) with 3 double bonds (18 3 i 15) ... 

Figure 8.11 The fluid-mosaic model of membrane structure. Phosphoglycerides are the chief lipid component. They are arranged in a bilayer. Proteins float like icebergs in a sea of lipid.

Polyunsaturated fatty acids are recognized to be essential for humans and animals for two reasons synthesis of lipid mediators and production of membranes that have the optimum lipid bilayer structure and functional properties. The main function of co-3 fatty acids is related to membrane structure, and DHA plays a role. The polyunsaturated CO-6 fatty acids have a role in formation of hpid mechators, which includes the eicosanoids and the inositol phosphoglycerides. Arachidonic add is the main fatty acid of the co-6 family involved in this process however, EPA also can play a role in the formation of eicosanoids. ... 

Cholesterol The pathway for synthesis of cholesterol is described in Appendix 11.9. Cholesterol is important in the structure of membranes since it can occupy the space that is available between the polyunsaturated fatty acids in the phospholipid (Chapter 4). In this position, cholesterol restricts movement of the fatty acids that are components of the phosphoglycerides and hence reduces membrane fluidity. Cholesterol can be synthesised de novo in proliferating cells but it can also be derived from uptake of LDL by the cells, which will depend on the presence of receptors for the relevant apoUpoproteins on the membranes of these cells (Appendix 11.3). 

Two main types of lipids occur in biological membranes phospholipids and sterols. The predominant phospholipids in most membranes are phosphoglycerides, which are phosphate esters of the three-carbon alcohol, glycerol. A typical structure is that of phosphatidylcholine (lecithin) ... 

Structure of a lipid bilayer membrane. Phosphoglycerides can aggregate into a bilayer membrane with their polar heads exposed to the aqueous solution and the hydrocarbon tails protected within. This lipid bilayer is an important part of the cell membrane. 

An aggregation of phosphoglycerides with the hydrophilic heads forming the two surfaces of a planar structure and the hydrophobic tails protected within. A lipid bilayer forms part of the animal cell membrane, (p. 1210)... 

Phospholipids, which are responsible for the structure of the cell membrane, are easily accessed through simple extraction procedures providing a useful biomarker for microbial detection and identification. However, they are influenced by the growth conditions, nutritional status, and history of a microorganism. These factors cause changes in the phospholipid (phosphoglyceride) profile as the microbe changes its membrane composition in response to its environmental requirements. 

Phospholipids are structural components of membranes. There are two types of phospholipids phosphoglycerides and sphingomyelins. 

Problem 19.33. Ionic head portions are not present in all membrane lipids. The other phospholipids, the plasmalogens and sphingomyelins, are like the phosphoglycerides in having an ionic head and two nonpolar tails, but the glycolipids and cholesterol do not possess ionic heads. What is the structural feature common to all membrane lipids ... 

Cell membranes have a fluid mosaic structure. The term fluid conveys the fluid (flexible) or liquid-like nature of the cell membrane. The term mosaic conveys the complex nature of cell membranes in terms of their structure and composition. Not only does the lipid bilayer contain different lipids (phosphoglycerides, plasmalogens, sphingomyelins, glycolipids, cholesterol), it also contains a variety of proteins essential to cell function. The physiological function of a membrane depends on its fluidity, which varies with the relative amounts of saturated fatty acids, unsaturated fatty acids, and cholesterol. 

A great deal of research from several laboratories, including ours, has given a picture, incomplete, to be sure, of the many reactions that combine to determine the composition of the brain lipids. These are outlined in Fig, 1, which provides an overview of the sources and metabolic transformations of the fatty acids that contribute their properties to the major phosphoglycerides and sphingolipids that form the chief structural units of the membranes that are involved in most of the properties of the brain. 

Lipids are important in the structural integrity of cells and comprise the major components of all membranes (Vandenheuvel, 1971). Lipids of importance in these roles are sterols, phosphoglycerides, glycolipids, and sphingolipids. 

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