Animal cells, illustrations

The Vinca alkaloids metabolism and transport in the producing plant cells and in the treated animal cells illustrate some interesting aspects of how evolution can be winding and parsimonious in the solutions it creates. 

In spite of the variety of appearances of eukaryotic cells, their intracellular structures are essentially the same. Because of their extensive internal membrane structure, however, the problem of precise protein sorting for eukaryotic cells becomes much more difficult than that for bacteria. Figure 4 schematically illustrates this situation. There are various membrane-bound compartments within the cell. Such compartments are called organelles. Besides the plasma membrane, a typical animal cell has the nucleus, the mitochondrion (which has two membranes see Fig. 6), the peroxisome, the ER, the Golgi apparatus, the lysosome, and the endosome, among others. As for the Golgi apparatus, there are more precise distinctions between the cis, medial, and trans cisternae, and the TGN trans Golgi network) (see Fig. 8). In typical plant cells, the chloroplast (which has three membranes see Fig. 7) and the cell wall are added, and the lysosome is replaced with the vacuole. 

Fig. 4. A schematic illustration of the membrane structure of a hypothetical eukaryotic (animal) cell.

Specific damage to bacteria is particularly practicable when a substance interferes with a metabolic process that occurs in bacterial but not in host cells. Clearly this applies to inhibitors of cell wall synthesis, because human and animal cells lack a cell wall. The points of attack of antibacterial agents are schematically illustrated in a grossly simplified bacterial cell, as depicted in (2). 

The illustration shows a model of a small section of a membrane. The phospholipids are the most important group of membrane lipids. They include phosphatidylcholine (lecithin), phosphatidylethanolamine, phos-phatidylserine, phosphatidylinositol, and sphingomyelin (for their structures, see p. 50). in addition, membranes in animal cells also contain cholesterol (with the exception of inner mitochondrial membranes). Clycoli-pids (a ganglioside is shown here) are mainly found on the outside of the plasma membrane. Together with the glycoproteins, they form the exterior coating of the cell (the gly-cocalyx). 

Fig. 1.52. Model for the control of translation by tubulin. The amount of tubuhn in animal cells is determined partially by the stabrhty of P-tubuhn mRNA, whereby tubuhn itself acts as the regulating signal. Starting from the 5 cap, various stages of the translation of P-tubuhn mRNA, represented as a chain of small circles, is illustrated in the figure. As soon as the N-terminus of the growing P-chain emerges from the ribosome, the a- and P- subunits of tubulin bind to the terminal MREI sequence, upon which an endonuclease becomes activated by a presently unknown mechanism. The degradation of the P-tubulin mRNA then proceeds.

Fig. 1. (A) Illustration of a generalized animal cell including many of the organelles...

Fig. 1. The accuracy of e-beam lithography is illustrated in the scanning electron micrograph (top). The size of the features formed in the silicon oxide is 0.5 pm and the typical animal cell (a fibroblast) has a diameter of 20 pm. This kind of cell adheres actively to surfaces, forming thin filopodia which here have all attached to the micro-hillocks. Semiconductor technology is capable of manufacturing micro-electrodes, sensors, pores and electronic networks with sizes smaller than that of the cell. The lower illustration summarises the main detection and measuring methods currently in use...

Fig. 18. Diagrams illustrating the differences and difficulties during freezing of cells in suspension (a) and on surfaces (b, c and d). In both cases, large ice crystal formation must be avoided, this means that freezing must be rapid and often involves the use of cryo-protectants. In suspension, the use of hypertonic solutions to shrink cells by osmosis helps to avoid membrane rupture. But with cells fixed to surfaces, shrinkage can lead to rupture of the filopodia or to parts of cytoskeleton or cell membrane (c). Additionally, animal cells under stress (including this kind of osmotic stress) tend to build up into a spherical shape. This means they would lose many of their surface contacts before freezing and disappear into solution after re-thawing. Cryo-con-servation of adhered cells in defined positions requires very precise control of the conditions...

Kinetics models for cell growth and death, as well as for substrate consumption and product and byproduct synthesis, are presented here. Most of these were developed for hybridomas in continuous processes. Although these models are representative of animal cell systems, it is important to understand that the cellular response to an environmental stimulus is highly dependent on the specific cell line. The review published by Porter and Schafer (1996) illustrated this variability through the comparison of experimental data and models from different groups of cell lines. Besides this, the lack of proper knowledge to explain experimentally observed phenomena also accounts for the variability of model structures. 

The construction of a kinetic model for an animal cell culture involves several steps a kinetic analysis of the experimental results with the formulation of hypotheses on the nature of the rate-limiting steps the choice of rate expressions describing the influence of these phenomena on the cellular processes evaluation of parameter values and validation of the model with different experimental results. In this section a general methodology is described for the modelling of cell cultures, and the procedure is illustrated on the kinetics of a hybridoma cell. (For a summary of terms used, see Table 4.3.3.)... 

FIGURE 1-7 Eukaryotic cell structure. Schematic illustrations of the two major types of eukaryotic cell (a) a representative animal cell and (b) a representative plant cell. Plant cells are usually 10 to 100 p,m in diameter—larger than animal cells, which typically range from 5 to 30 p,m. Structures labeled in red are unique to either animal or plant cells. 

Mitochondria - Figure 24.39 illustrates the unusual DNA replication initiation scheme employed by animal cell mitochondria. This involves two unidirectional replication processes. 

Plasma membrane potential of animal cells The membrane potential of whole cells is more difficult to assess than that of isolated organelles with optical indicators because cells contain many sub-ccllular compartments, and it is necessary to isolate the response of the plasma membrane from that of any other cell membrane. For example, the intense staining of mitochondria by cyanine dyes (7). which are membrane-permeant cations, means that if you choose a cyanine dye, or other lipophilic cation, lo measure plasma membrane potential it is important to establish conditions where the mitochondrial potential is disabled. If an anionic dye is chosen, this problem is overcome but there is, then, very little entry of dye into the cells unless the dye is itself reasonably lipophilic. Thus, for studies of whole cells, we employ an oxonol dye with a phenyl substituent. The procedures fijr mc.isuring plasma membrane potential with this dye, oxonol-V (31), are illustrated in R,giirf. j and Protocol 2. 

FIGURE 18.2 The diagram illustrates the major components of a typical animal cell. What is the function of the mitochondria in a cell ... 

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