Microbial Metabolism

• Metabolism is the series of biochemical reactions by which the cell breaks down or biosynthesizes various metabolites
• Nutrient requirements differ due to the metabolic capacities of microbes
• Elements predominant in the cell: C, H, O, N, P, S
• Carbon: Needed in the largest amount, amounting to 50% of a cell's dry weight
• Oxygen and hydrogen: Cover 25% of a cell's dry weight when combined
• Nitrogen: Occupies 13% of the cell's dry weight
• Phosphorus, Sodium, Potassium, Magnesium, and Selenium: Make up 5% of a cell's dry weight when combined
• Microbial nutrients: Macronutrients, Micronutrients
• Micronutrients: Trace elements as co-factor of certain enzymes, Vitamins as growth factors (organic micronutrient), Iron (Fe) plays a major role in cellular respiration
• Active transport of nutrients is energy requiring process driven by ATP (or some other energy-rich compound) or by the proton motive force
• Classes of transport systems: Simple, Group translocation, ABC systems
• Simple transport is major transport systems comprising of reactions that are driven by the energy inherent in the proton motive force
• Symport reactions is a type of simple transport
• Antiport reactions is another type of simple transport
• Group translocation is the transported substance is chemically modified during the transport process, driven by an energy-rich organic compound
• ABC transport systems is transport systems that employ a periplasmic binding protein along with transmembrane and ATP-hydrolyzing components
• Energy classes of microorganisms: Chemotrophs, Phototrophic organisms
• Chemotrophs is organisms that conserve energy from chemicals
• Chemoorganotrophs is use organic chemicals as their electron donors
• Chemolithotrophs is use inorganic chemicals as their electron donors
• Phototrophic organisms is convert light energy into chemical energy (ATP)
• Heterotroph its cell carbon is obtained from one or another organic compound
• Autotroph is uses carbon dioxide (CO2) as its carbon source
• Most chemolithotrophs and phototrophs are autotrophs
• Autotrophs are also called primary producers because they synthesize new organic matter from inorganic carbon (CO2)
• Calvin cycle is the major biochemical pathway by which phototrophic organisms incorporate CO2 into cell material
• Enzymes is protein catalysts that increase the rate of biochemical reactions by activating the substrates that bind to their active site
• Enzymes are highly specific in the reactions they catalyze, and this specificity resides in the three-dimensional structures of the polypeptide(s) that make up the protein(s)
• Redox reactions is chemical reactions in the cell accompanied by changes in energy, expressed in kilojoules
• ∆G0 is a measure of the energy released or consumed in a reaction under standard conditions, revealing which reactions can be used by an organism to conserve energy
• Reduction potential (E0') is expresses the tendency of a compound to accept or release electrons
• Redox reactions in a cell often employ redox coenzymes such as NAD+/NADH as electron shuttles
• ATP is the prime energy carrier in the cell, consisting of the ribonucleoside adenosine to which three phosphate molecules are bonded in series
• Categories of metabolism: Anabolism, Catabolism
• Anabolism is any process that results in synthesis of cell molecules and structures, consumes energy
• Catabolism is breaks the bonds of larger molecules into smaller molecules, releases energy
• Much of the energy released during catabolic reactions is used to drive anabolic reactions
• Glycolysis is the Embden-Meyerhof-Parnas pathway, the universal pathway for the catabolism of glucose
• The glycolytic pathway is used to break down glucose to pyruvate and is a widespread mechanism for energy conservation by fermentative anaerobes that employ substrate-level phosphorylation
• The glycolytic pathway releases a small amount of ATP (2–3/glucose) and large amounts of fermentation products