Catabolism carbohydrates

Kohlenhydrat, n. carbohydrate, -abbau, m. carbohydrate degradation, specif, carbohydrate catabolism, -stoffwechsel, m. carbohydrate metabolism, -verwertung, /. carbohydrate utilization. 

Carbohydrate metabolism in the organism tissues encompasses enzymic processes leading either to the breakdown of carbohydrates (catabolic pathways), or to the synthesis thereof (anabolic pathways). Carbohydrate breakdown leads to energy release or intermediary products that are necessary for other biochemical processes. The carbohydrate synthesis serves for replenishment of polysaccharide reserve or for renewal of structural carbohydrates. The effectiveness of various routes of carbohydrate metabolism in tissues and organs is defined by the availability of appropriate enzymes in them. 

Suppose we start with a starch-rich meal, say one containing a lot of pasta or bread. The digestion of starches begins in the mouth. Saliva contains an enzyme, salivary amylase (aka ptyalin), which catalyzes the conversion of starch to simple sugars such as glucose. This process is completed in the small intestine under the influence of other enzymes in the amylase class. This completes the first phase of carbohydrate catabolism the conversion of complex, polymeric carbohydrates (e.g., starches) to their simple monomeric units, the sugars. 

Metabolic reactions are of two general kinds. Catabolism includes all reactions that break down large molecules into smaller ones with a release of energy, as in the breakdown of carbohydrates. Catabolic reactions are also called destructive metabolism. 

Interest has focussed on four main areas (a) the nature of exogenous carbohydrates utilised by cestodes, (b) the mechanisms by which these carbohydrates are absorbed, (c) the pathways of carbohydrate catabolism and (d) the regulatory control of these pathways. 

These investigations have shown that cestodes, in common with other parasitic helminths, utilise carbohydrate as the major, and possibly only, energy substrate. In addition, carbohydrate catabolism in cestodes is characterised by the excretion of reduced end-products (e.g. lactate, propionate, succinate) even under aerobic conditions. 

Korting, W. Barrett, J. (1977). Carbohydrate catabolism in the plerocercoids of Schistocephalus solidus (Cestoda Pseudophyllidea). International Journal for Parasitology, 7 411-17. 

T3i metabcJic breakdown of triacylglyceroJs bt ns with their hydrelyjis ia the stomach and small intestine to yiold glycerol plus fatty adds. Cl>verot is first phoopho-rylated by reaction with ATP and is thm oxidised to yield ycenildeh e 3 phosphate. which enters the carbohydrate catabolic path way. (Well scuss this in detail in Section 2. 3.)... 

Fig. 3. —Interrelationships of the Central Pathways of Carbohydrate Catabolism in Yeasts.

Relationship of Fatty Acid Synthesis to Carbohydrate Metabolism (Figure 18.22) Acetyl-CoA from fatty acid and carbohydrate catabolism can be made into... 

FIG. 3.1 Main types of subcellular organization of carbohydrate catabolism in eukaryotes. (A) No compartmentation (Giardia sp., Entamoeba sp.) (B) cytosolic/hydrogenosomal compartmentation (Trichomonas vaginalis, other trichomonads) (C) cytosolic/mitochondrial compartmentation (most eukaryotic cells). 1, hydrogenosome 2, mitochondrion. 

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