METABOLISM-CHO

• Nutrients needed by bacteria

  • C - Sugar, Lipid (Energy, Biosynthesis)
  • N - Protein (Biosynthesis)
  • O - Air (Energy)
• Enzymes


  Catalysts that speed up and direct chemical reactions

  
• Types of enzymes

  • Simple enzymes - consist of protein alone
  • Conjugated enzymes or holoenzymes - contain protein and nonprotein molecules
• Coenzymes


  • Niacin - NAD
  • Riboflavin - FAD
  • Pantothenic Acid - CoEnzyme A

  
• Types of enzymes

  • Constitutive enzymes - always present, always produced in equal amounts or at equal rates
  • Induced enzymes - not constantly present, produced only when substrate is present

  
• Enzyme Specificity


  Explained by the Lock and Key Theory
• Enzyme catalysis


  E + S
• Transfer reactions by enzymes

  • Oxidation-reduction reactions - transfer of electrons
  • Aminotransferases - convert one type of amino acid to another by transferring an amino group
  • Phosphotransferases - transfer phosphate groups, involved in energy transfer
  • Methyltransferases - move methyl groups from one molecule to another
  • Decarboxylases - remove carbon dioxide from organic acids
• Inhibitors that effect enzymatic activity

  • Competitive Inhibitors
  • Noncompetitive Inhibitors

  
• Competitive Inhibitors


  • Penicillin - competes for the active site on the enzyme involved in the synthesis of the pentaglycine crossbridge
  • Sulfanilamide (Sulfa Drugs) - competes for the active site on the enzyme that converts PABA into Folic Acid

  
• Control of enzyme activity

  • Competitive inhibition - substance that resembles normal substrate competes with substrate for active site
  • Feedback inhibition - concentration of product at the end of a pathway blocks the action of a key enzyme
  • Feedback repression - inhibits at the genetic level by controlling synthesis of key enzymes
  • Enzyme induction - enzymes are made only when suitable substrates are present

  
• Chemical Preservatives


  • Benzoic Acid - Inhibit to enzyme in Glycolysis and TCA pathway
  • Sorbic Acid - Inhibition may cause cell death, slowing of growth

  
• Metabolic Activity Tests


  • Adenosine Triphosphate Assay
  • Catalase Test
  • Electrical Impedance Test
  • Microcalorimetry
  • Pyruvate Estimation

  
• Benefits of studying metabolism of bacteria in food microbiology

  • Can prolong shelf life of food product by control or block enzyme of the pathway
  • Can be used to detection contamination by looking at metabolic activity
• Focal Metabolite

  The few precursors for the biosynthetic origins of building blocks and coenzymes

  
• Carbon Sources


  • Glucose - the most common carbon source
  • Embden–Meyerhof–Parnas (EMP) pathway, glycolysis
  • Entner–Doudoroff (ED) pathway
  • Pentose phosphate (PP) pathway
  • Tricarboxylic acid cycle, TCA cycle, Kreb's cycle, citric acid cycle

  
• Carbohydrate Catabolism


  Microorganisms oxidize carbohydrates as their primary source of energy
• Fermentation


  Incomplete oxidation of glucose or other carbohydrates in the absence of oxygen, uses organic compounds as terminal electron acceptors, yields a small amount of ATP

  
• Types of Fermentation


  • Lactic Acid Fermentation
  • Alcohol Fermentation
  • Mixed-Acid Fermentation
  • Propionic Acid Fermentation

  
• Lipid Metabolism

  Lipids are essential to the structure and function of membranes, and function as energy reserves
• Lipid Catabolism


  Triacyglycerol is broken down by lipase into glycerol and 3 fatty acids, which undergo β-oxidation

  
• Photosynthesis


  Conversion of light energy from the sun into chemical energy, used to reduce CO2 to sugar, recycling of carbon in the environment
• Photosynthetic organisms


  • Green Plants
  • Algae
  • Cyanobacteria
• Photosynthesis


  6 CO2 + 6 H2O + sunlight
• Parts of Photosynthesis


  • Light Reaction
  • Dark Reaction