. Cytology. Cytology. chemical groups are associated with the surface of the proteins and the side chains connecting different proteins. These molecular groupings serve to connect protein molecules with each other and with lipid and carbohydrate molecules. The water of protoplasm is either bound to ionized groups of proteins, exists free, or is associated with mobile molecules. Assuming that this concept of the structure of protoplasm is essentially correct, fixation would involve the formation of new cross. Figure 11-1, Schematic Representation of the Molecular Organization of Protoplasm in t
. Cytology. Cytology. chemical groups are associated with the surface of the proteins and the side chains connecting different proteins. These molecular groupings serve to connect protein molecules with each other and with lipid and carbohydrate molecules. The water of protoplasm is either bound to ionized groups of proteins, exists free, or is associated with mobile molecules. Assuming that this concept of the structure of protoplasm is essentially correct, fixation would involve the formation of new cross. Figure 11-1, Schematic Representation of the Molecular Organization of Protoplasm in the Native State. The thick, wavy chains represent protein molecules—the fibrous ones being linear, the curved ones globular. The thick, straight chains represent lipid molecules and fatty acid radicals. The dots represent water molecules and crystalloids. Intermolecular linkages are shown as dashed lines; intramolecular linkages as solid lines. (From Wolman, M., 1955. "Problems of Fixation in Cytology, Histology, and Histochemis- try," Intern. Rev. Cytol., 4, Fig. 1, p. 89.) linkages between protein molecules, with the result that new forces of attraction would be established. If the new linkages developed in this way produce excessive clumping of proteins, the result is displacement and distortion of protein structures in the cell and, hence, "poor" fixation (Figure 11-2(b)). On this same basis, a "good" fixative would be one which leads to the formation of many cross linkages between proteins, none of which set up attraction forces of sufficient magnitude to disturb radically the spatial relations already existing between the proteins of the cell (Figure ll-2(a)). Fixing agents such as formaldehyde, dichromate, and mercuric chlo- SURVEY OF CYTOLOGICAL TECHNIQUES / 211. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may
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