Cytoplasm organic pathways 152

Fig. 4.7. A scheme for the organic pathways in the cytoplasm of all cells illustrating their interconnected nature (after Kauffman see Further Reading), (a) Glycolytic (b) Krebs cycle pathways.

The late cannabinoid pathway starts with the alkylation of ohvetolic acid (3.2 in Fig. 4) as polyketide by geranyl diphosphate (3.1) as the terpenoid unit. Terpenoids can be found in all organisms, and in plants two terpenoid pathways are known, the so called mevalonate (MEV) and non-mevalonate (DXP) pathway as described by Eisenrich, lichtenthaler and Rohdich [23,24,29,30]. The mevalonate pathway is located in the cytoplasm of the plant cells [30], whereas the DXP pathway as major pathway is located in the plastids of the plant cells [29] and delivers geranyl diphosphate as one important precursor in the biosynthesis. 

Glycolysis is a catabolic pathway in the cytoplasm that is found in almost all organisms— irrespective of whether they live aerobically or anaerobically. The balance of glycolysis is simple glucose is broken down into two molecules of pyruvate, and in addition two molecules of ATP and two of NADH+H"" are formed. 

The mevalonate-independent pathway is present in most bacteria and all phototropic organisms. In higher plants and most algae both pathways run independently. The mevalonate pathway is located in the cytoplasm and is responsible for the biosynthesis of most sesquiterpenoids. The mevalonate-independent pathway, in contrast, is restricted to the chloroplasts where plastid-related isoprenoids such as monoterpenes and diterpenes are biosynthesised via this pathway [43-45]. Figure 4.2 illustrates the interrelationships of both biosynthetic pathways connected to Fig. 4.1 [46]. 

The internal volume bounded by the plasma membrane, the cytoplasm (Fig. 1-3), is composed of an aqueous solution, the cytosol, and a variety of suspended particles with specific functions. The cytosol is a highly concentrated solution containing enzymes and the RNA molecules that encode them the components (amino acids and nucleotides) from which these macromolecules are assembled hundreds of small organic molecules called metabolites, intermediates in biosynthetic and degradative pathways coenzymes, compounds essential to many enzyme-catalyzed reactions inorganic ions and ribosomes, small particles (composed of protein and RNA molecules) that are the sites of protein synthesis. 

Despite this complexity, most integrins share two, key interrelated functions first, to promote the assembly and organization of the actin cytoskeleton [122, 123] and second, to regulate signal transduction cascades [124-126], Spanning the cell membrane, these subunits serve as a communication pathway, linking the actin cytoskeleton and intracellular cytoplasmic proteins involved in focal adhesion complexes (FACs) with the cell s dynamic extracellular environment (Fig. 8) [127-130]. There are at least 50 distinct proteins known to be involved in FACs. Actin [131], vinculin, talin, tensin, a-actinin, and filamin provide a structural role, while focal adhesion kinase [132], integrin-linked kinase, Src-family kinase, PINCH, paxillin... 

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