Microbial Metabolism

• Metabolism is the series of biochemical reactions by which the cell breaks down or biosynthesizes various metabolites.
• Cells are primarily composed of elements C, H, O, N, P, and S. These chemical elements are predominant in the cell.
• Carbon is 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.
• All microbes require a core set of nutrients.
• Macronutrients are required in large amounts.
• Micronutrients are required in small amounts
• The active transport of nutrients into the cell is an energy requiring process driven by ATP
• Three classes of transport systems:

  • simple transport
  • group translocation
  • ABC systems
• Simple transport - Major transport systems comprising of reactions that are driven by the energy inherent in the proton motive force.
• What is this called?

  A) Simple Transport

  
• Group translocation - The transported substance is chemically modified during the transport process.
• An energy-rich organic compound drives the transport event.
• What is it called?

  Answer: Group Translocation

  
• Microbes can be metabolically classified according to their carbon and energy source.
• Chemotrophs - organisms that conserve energy from chemicals
• Chemoorganotrophs use organic chemicals as their electron donors, while chemolithotrophs use inorganic chemicals.
• Phototrophic organisms convert light energy into chemical energy (ATP) and include both oxygenic and anoxygenic species.
• Heterotroph, its cell carbon is obtained from one or another organic compound.
• An autotroph, by contrast, uses carbon dioxide (CO2) as its carbon source.
• “ABC” stands for ATP-binding cassette – a structural feature of proteins that bind ATP
• ABC transport system - Transport systems that employ a periplasmic binding protein along with transmembrane and ATP-hydrolyzing components.
• 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.
• what is it called?

  A) enzymes

  
• Enzymes are 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 - Chemical reactions in the cell are accompanied by changes in energy, expressed in kilojoules. Reactions either release or consume free energy
• Oxidation–reduction reactions require electron donors and electron acceptors
• The substance oxidized (H2 ) as the electron donor, and the substance reduced (O2 ) as the electron acceptor.
• The energy released in redox reactions is conserved in compounds that contain energy-rich phosphate or sulfur bonds.
• ATP – the prime energy carrier in the cell
• Redox reactions in a cell often employ redox coenzymes such as NAD+/NADH as electron shuttles.
• Metabolism pertains to all chemical reactions and physical workings of the cell.
• Two categories of metabolism:

  1. Anabolism
  2. Catabolism
• Anabolism – any process that results in synthesis of cell molecules and structures
• • A building and bond-making process that forms larger macromolecules from smaller ones and consumes energy

  What is it called?

  Answer: Anabolism