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Microbial Metabolism: Catabolic and Anabolic Reactions:

Microbial Metabolism: Catabolic and Anabolic Reactions:. All cells require a constant supply of energy to survive. This energy, typically in the form of ATP, is derived from the ordered breakdown of various organic substrates(carbohydrates, lipids, and proteins ).

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Microbial Metabolism: Catabolic and Anabolic Reactions:

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  1. Microbial Metabolism:Catabolic and Anabolic Reactions: All cells require a constant supply of energy to survive. This energy, typically in the form of ATP, is derived from the ordered breakdown of various organic substrates(carbohydrates, lipids, and proteins). This process of substrate breakdown and conversion into usable energy is known as Catabolism. The energy produced may then be used in the biosynthesis of cellular constituents ( cell wall, proteins, fatty acids, and nucleic acid), in a processes known as Anabolism.

  2. a In another words, anabolismis a polymerization of biochemical building blocks into protein, nucleic acid, polysaccharides and lipids. Together these two processes are referred to as metabolism. The specific metabolic pathway used by bacteria for the breakdown and synthesis of organic substrates are shared by all living cells( prokaryotic and eukaryotic cell). These similarities form the basis for the concept of the unity of biochemistry.

  3. a Unity of biochemistry means similarities in the following: 1- Mechanisms for the synthesis of energy as ATP. 2- Synthesis and function of genetic code. 3- Metabolic pathways for degrading carbohydrates, proteins and lipids.

  4. Biochemical pathway of energy production: Glycolysis: Tricarboxylic acid cycle: Electron transport chain: Glycolysis: Bacteria utilize three major metabolic pathways in the catabolism of glucose. Most common among these is the glycolytic pathway . This pathway represents the primary means in both bacteria and Eukaryotic cells for the conversion of glucose to pyruvate, which is central to variety of other cellular metabolic pathways. These reactions begin with activation of glucose to form glucose-6-phosphate.

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  6. a Energy is produced during glycolysis in two different reactions: 1- 3-phosphoglycerol phosphate→ kinase( ADP→ATP)→ 3- phosphoglycerate 2- 2-phosphoenolpyruvate→→kinase(ADP→ATP)→→pyruvate This process called substrate level phosphorylation. Four ATP molecules was produced per one molecule of glucose , so net energy production is 2 ATP molecules per one glucose. In the absence of oxygen, the pyravate will be converted to lactic acid by bacteria (bacterial fermentation). Pyravic acid will be converted to alcohol by yeast under the same conditions ( yeast fermentation).

  7. Tricarboxylic acid cycle: In presence of oxygen, the pyruvic acid produced from glycolysis may be completely oxidized to CO2 using TCA cycle which results in the production of additional energy. The process begins with the oxidative decarboxylation of Pyruvate to high-energy molecule; Acetyl-coA. CO2─C ─CH3→ Pyruvate decarboxylase (NAD→NADH) →CH3CScoA Net reaction: Acetyl-coA+ 3 NAD+ FAD+ GDP+ Pi→HScoA+2 CO2+ 3NADH+ FADH2+ GTP

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  9. Electron transport chain: It is a protein chain associated to cell membrane of bacterial cell and responsible to sequential oxidation steps working for energy generation. In this chain, the electrons carried by NADH ( FADH) arepassedin a stepwise manner through a series of (donor /acceptor) pair of proteins and then to oxygen.

  10. A This process known as Aerobic respirationresults in the generation of 3 moles of ATP per mole of NADH and 2 moles of ATP per mole of FADH . Energy production per one glucose molecule will be calculated to be 38 ATP molecules.

  11. Biochemical pathway of energy utilization (Biosynthesis): Microbial growth requires the polymerization of biochemical building blocks into proteins, nucleic acid, polysaccharides, and lipids. The building blocks must be added to culture media or must be synthesized by the growing cells. Biosynthesis of coenzymes ( enzyme catalysis) is required for cell growth and division. Biosynthetic polymerization reactions demand the transfer of anhydride bonds from ATP.

  12. a The building blocks can be synthesized from few precursors called focal metabolites and this process required ATP. These are responsible for biosynthesis of amino acids, polysaccharides, lipids, and nucleic acid precursors from focal metabolites. Focal metabolites are: glucose-6-phosphate, oxaloacetate,phosphoenolpyruvate, and alpha- ketoglutarate.

  13. Biosynthesis of Lipopolysccharid: Lipopolysccharid molecule is composed of three main regions: 1- The hydrophobic lipid A. 2- The core polysaccharide. 3- The hydrophilic O-antigen In the bacterial cytoplasm, addition of fatty acids to disaccharide-diphosphate to form lipid A. Lipid A is hydrophobic in nature; this allows it to become dissolved in the cytoplasmic membrane. Core polysaccharide will be added to lipid A by enzyme activity and energy (ATP) in the cell membrane to form LPS.

  14. Nucleic acid biosynthesis 1-DNA replication 2- Transcription of DNA. Protein biosynthesis: Translation

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