LEC #5

• Metabolism


  The series of biochemical reactions by which the cell breaks down or biosynthesizes various metabolites
• Cells


  • Must incorporate nutrients from the environment, transform them into precursor molecules, and then use them to construct a new cell
  • Metabolic capacities of microbes differ, their nutrient requirements also differ
• Elements predominant in the cell


  • Carbon
  • Hydrogen
  • Oxygen
  • Nitrogen
  • Phosphorous
  • Sulfur
• 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 (required in large amounts)
  • Micronutrients (required in minute amounts)
• Active transport of nutrients into the cell


  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


  Major transport systems comprising of reactions that are driven by the energy inherent in the proton motive force
• Symport reactions


  A type of simple transport
• Antiport reactions


  A type of simple transport
• Group translocation


  The transported substance is chemically modified during the transport process, driven by an energy-rich organic compound
• Energy classes of microorganisms

  • Chemotrophs (conserve energy from chemicals)
  • Phototrophic organisms (convert light energy into chemical energy)
• Chemoorganotrophs


  Chemotrophs that use organic chemicals as their electron donors
• Chemolithotrophs


  Chemotrophs that use inorganic chemicals as their electron donors
• Heterotroph


  Its cell carbon is obtained from one or another organic compound
• Autotroph


  Uses carbon dioxide (CO2) as its carbon source
• ABC transport systems


  Transport systems that employ a periplasmic binding protein along with transmembrane and ATP-hydrolyzing components
• Most chemolithotrophs and phototrophs are autotrophs, also called primary producers because they synthesize new organic matter from inorganic carbon (CO2)
• Calvin cycle


  The major biochemical pathway by which phototrophic organisms incorporate CO2 into cell material
• Enzymes


  • Protein catalysts that increase the rate of biochemical reactions by activating the substrates that bind to their active site
  • 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


  • Chemical reactions in the cell accompanied by changes in energy, expressed in kilojoules
  • Require electron donors and electron acceptors, the tendency of a compound to accept or release electrons is expressed by its reduction potential (E0')
• ATP

  Means, Adenosine triphosphate. The prime energy carrier in the cell, consists of the ribonucleoside adenosine to which three phosphate molecules are bonded in series
• Redox coenzymes


  Such as NAD+/NADH, act as electron shuttles in redox reactions
• Categories of metabolism

  • Anabolism (any process that results in synthesis of cell molecules and structures)
  • Catabolism (breaks the bonds of larger molecules into smaller molecules)
• Anabolism

  A building and bond making process that forms larger macromolecules from smaller ones, consumes energy
• Catabolism


  Releases energy
• Glycolysis


  The Embden-Meyerhof-Parnas pathway, the universal pathway for the catabolism of glucose, releases a small amount of ATP (2–3/glucose) and large amounts of fermentation products

  
• Respiration


  Offers an energy yield much greater than that of fermentation
• Glyoxylate cycle


  Necessary for the catabolism of two carbon electron donors, such as acetate
• Electron transport chain


  Composed of membrane associated redox proteins that are arranged in order of their increasing E0' values, functions to carry electrons from the primary electron donor to the terminal electron acceptor, which is O2 in aerobic respiration
• Biosynthesesor anabolic reactions


  involve the assembly of smaller molecules into larger molecules, requiring the formation of bonds. Once formed, the bonds represent stored energy.
• Phototrophy


  The use of light energy is prevalent in the microbial world
• Photosynthesis


  Considered the most important biological process
• Phototrophs


  Organisms that carry out photosynthesis
• Autotrophs


  Photosynthetic organisms that are capable of growing with carbon dioxide as the sole source of carbon
• Photoautotrophs


  Energy comes from light is used in the reduction of CO2 to organic compounds
• Photoheterotrophs


  Phototrophs that use organic carbon as their carbon source