MICROBIAL METABOLISM Metabolism is a requirement for life. It is the means by which all life forms, including microorganisms, obtain and use energy. This energy is required for growth, repair, and maintenance of the chemical and physiological processes of the cell. Energy is also needed to maintain the structural integrity of the cell by repairing or replacing damaged components. What is Metabolism?Metabolism: Metabolism is a general term forall of the biochemical reactions taking place within an organism. The biochemical reactions of metabolism fall into 2 broad categories; 1) anabolism, and 2) catabolism.
Anabolism is the set of metabolic reactions that create or synthesize larger, more complex molecules from smaller ones. Anabolism involves the process of creating or building chemical bonds, which requires energy in the form of ATP. Reactions that require energy are called endergonic. What Types of Substances are Metabolized? Living organisms typically need a steady supply of at least the following four important classes of organic molecules: Carbohydrates (sugars) monosacharrides (simple sugars) disacharrides (simple sugars) polysaccharides(complex carbohydrates) Lipids (fats) saturated fats unsaturated fats polyunsaturated fats trans-fats Proteins amino acids dipeptides, tripeptides, polypeptides Nucleic Acids ( RNA and DNA ) Living organisms must synthesize polymers of these important molecules in order to sustain life. Similarly, these molecules can be broken down to release energy or to use as building blocks for other molecules that the organism may need at the time. These would be the catabolic reactions of metabolism. For example, cells must maintain their structural integrity by constantly replacing its damaged components. This maintenance process involves the synthesis of new molecules and polymers. Anabolic reactions of metabolism are used to polymerize amino acids into proteins that can function as structural proteins within the cell, or they can function as enzymes which assist the chemical reactions taking place in the cell. Formation of a Peptide Bond
Most microorganisms obtain their energy from the nutrients they take into the cell (see microbial growth and nutrition page). For microorganisms, these nutrients may come from either an organic or an inorganic source. Once the energy-giving nutrients enter the cell, they must be chemically processed so that they can be used. They are of no use to the cell in their "raw" form. The chemical processing that takes place involves a series of chemical reactions that will function to trap some of their chemical energy and to break down the larger molecules into smaller molecules that can be used as building blocks for the synthesis of new cellular components. Anabolic reactions usually proceed as a condensation reaction. In a condensation reaction, hydrogen (H+) is removed from one of the monomers and a hydroxyl group (OH-) is removed from the other monomer. The hydrogen (H+) and the hydroxyl group (OH-) combine to form water (H2O) as a byproduct of the reaction. As this occurs, a covalent bond is formed.
While there are for each of these are synthesized as part of our anabolic reactions of our metabolism. Each of these classes of molecules are polymers that are made up of The four molecule Monosaccharides are joined via glycosidic linkages to form disaccharides and polysaccharides Amino acids are joined via peptide bonds to make polypeptide chains Glycerol and fatty acids are joined via an ester linkage to create triglycerides Nucleotides are joined by phosphodiester bonds to form polynucleotide chains Catabolism: Larger molecules are broken apart into smaller molecules bybreaking chemical bonds. This process releases energy in the form of ATP Reactions that release energy are called exergonic. For example, in glycolysis, a glucose molecule is split and energy is released. REQUIREMENTS FOR LIFE Carbon Source - Cells must consume molecules that have carbon in it. Carbon is needed for Lipids, Amino Acids, Nucleic Acids Energy Source - Cells processes require energy - Cells can use ATP to fuel its processes.