Metabolic pathways are series of chemical reactions catalyzed by enzymes and which occur within the cells of living organisms. These pathways help to regulate homeostasis in living cells. Metabolism is the sum total of biochemical reactions that occur in all living systems include man, plants, animals and microbes. These biochemical reactions can either be anabolic reactions (anabolism) or catabolic reactions (catabolism); and they are critical to the daily subsistence of living organisms in their natural habitat. In catabolic reactions, macromolecules are broken down to yield energy that is used to power anabolic processes in the body. And anabolic reactions are concerned with the building up of macromolecules from simpler precursors. While catabolic reactions are energy yielding processes, anabolic reactions are generally energy-requiring reactions.
Anabolic pathways require energy and build new molecules while a catabolic pathways produces energy and degrades molecules. Microorganisms have a variety of metabolic pathways which they use to generate important cellular and metabolic molecules critical for life. These metabolic processes are diverse and they include those that breakdown amino acids or proteins; carbohydrates and lipids. These biochemical reactions or metabolic pathways such as the glycolytic pathway and tricarboxylic acid (TCA) as shall be discussed in this section are catalyzed by enzymes; and they mainly operate like an electrical circuit in which electrons flow from one point to another and energy in the form of adenosine triphosphate (ATP) is also generated in the process.
Other important metabolic pathways of living organisms include the pentose-phosphate pathway, oxidative phosphorylation, gluconeogenesis, fatty acid metabolism, lipid metabolism, carbohydrate metabolism and urea metabolism amongst others. Despite the complexity of these metabolic pathways inclusive of those that control catabolic and anabolic pathway reactions are regulated in order to maintain a state of equilibrium within the living system. Metabolic pathways are complex network of chemical reactions catalyzed by enzymes; and which occur within the confines of a cell that can be analyzed in self-contained parts generally known as pathways. In these pathways, substrates or reacting molecules are initially activated and committed to the generation of important intermediates and precursors for the biosynthesis of other important molecules in the cell. Metabolic pathways in living systems can be controlled by several factors including the availability of substrates, the gene expression of the organism as well as the catalytic activity of the process. Examples of the different metabolic pathways in microorganisms and other living systems interlude: glycolysis or glycolytic pathway and Kreb’s cycle. These pathways are explained in the subsequent sections in detail.
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