Blood cells, membrane structure

Basic information on the mechanical analysis of biomembrane deformation can be found in Evans and Skalak [1979], which also appeared as a book under the same title (CRC Press, Boca Raton, FL, 1980). A more recent work that focuses more closely on the structural basis of the membrane properties is Berk et al, chapter 15, pp. 423-454, in the book Red Blood Cell Membranes Structure, Function, Clinical Implications edited by Peter Agre and John Parker, Marcel Dekker, New York, 1989. More detail about the membrane structure can be found in other chapters of that book. 

Lipids and proteins that are part of cell membranes often are bonded to small polysaccharide groups that project from the surface of the cell. Slight differences in the structures of polysaccharides that are bonded to lipids in red blood cell membranes of humans are responsible for the A, B, and O blood types. Antibodies recognize these groups and cause cells to clump when their surface groups are not the same as those on the cells of the original individual. 

Indeed, these situations can be observed in living cell structures. During electron microscopic observation of freeze-thawed cell nuclei, rapidly frozen specimens had the original tissue structure. When these specimens were thawed rapidly, no difference could be seen in comparison with the control. Only a minor increase in the affinity to dyes and a slight condensation of chromosome have been observed. On the contrary, when specimens are thawed slowly many large cavities are observed, which indicates that the cellular materials are forced out by ice crystals. In these specimens, a very serious rupture of nuclear membrane was also observed. Similar results have been obtained with freeze-fractured electron microscopic observation of rapidly frozen red blood cells. In these experiments, membrane structure had been damaged in the regions where ice crystals and red blood cell membranes were in close contact. 

Lenard, J. and Singer, S. J. (1968) Structure of membranes reaction of red blood cell membranes with phospholipase C. Science, 159, 738-739. 

During the last steps of lipid oxidation, the fatty acid chains breakdown to give aldehydes (hexanal, propanal, malondialdehyde), depending on the lipid structure. These compounds react with thiobarbituric acid to give coloured compounds the measurement of which at 535 nm can be used to follow the oxidation process in its terminal phase [91]. In addition, hexanal, which is an important decomposition product of n-6 polyunsaturated fatty acid peroxidation in rat liver samples, human red blood cell membranes, and human LDL (low density lipoproteins), can be measured by headspace gas chromatography [92]. Malondialdehyde, another important decomposition product, can also be analysed by GC (Gas Chromatography) [93], and, after reaction with urea to give 2-hydroxypyrimidine, by HPLC [94]. 

Waugh, R. and Evans, E.A. 1979. Thermoelasticity of red blood cell membrane. Biophys. J. 26 115-132. Waugh, R.E. and Marches , S.L. 1990. Consequences of structural abnormalities on the mechanical properties of red blood cell membrane. In Cellular and Molecular Biology of Normal and Abnormal Erythrocyte Membranes, C.M. Cohen and J. Palek, eds. pp. 185-199, Alan R. Liss, New York, NY. Yeung, A. and Evans, E. 1989. Cortical shell-liquid core model for passive flow ofliquid-like spherical cells into micropipets. Biophys. J. 56 139-149. 

The most important bilayers are formed by the phospholipids, shown in Figure 12.1(a).They form the membrane that covers the surface of our blood cells. Bilayer structures are stabilized by solvation of the head groups by water and by the nearly total avoidance of water by the hydrophobic hydrocarbon tails. We observe the same pattern in many self-assemblies found in nature, such as micelles, reverse micelles, and microemulsions, discussed later. 

Within this membrane structure sit protein molecules, in about equal weight to the lipids, and these cannot be readily removed because they are anchored by ten or twenty hydrophobic amino acids.For example, a red blood cell membrane contains largely glycophorin molecules which have 131 amino acid residues and about 100 saccharide residues arranged as 16 short carbohydrate chains about 1 nm long. ... 

The remainder of this chapter will deal with natural polymers. These are large molecules, produced by plants and animals, that carry out the many life-sustaining processes in a living cell. The cell membranes of plants and the woody structure of trees are composed in large part of cellulose, a polymeric carbohydrate. We will look at the structures of a variety of different carbohydrates in Section 23.3. Another class of natural polymers are the proteins. Section 23.4 deals with these polymeric materials that make up our tissues, bone, blood, and even hair. ... 

Figure 47-2. Structures of two 0-linked oligosaccharides found in (A) submaxillary mucins and (B) fe-tuin and in the sialoglycoprotein of the membrane of human red blood cells. (Modified and reproduced, with permission, from LennarzWJ The Biochemistry of Glycoproteins and Proteoglycans. Plenum Press, 1980.)...

The red blood cell is simple in terms of its structure and function, consisting principally of a concentrated solution of hemoglobin surrounded by a membrane. 

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