Microorganisms Quiz
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Questions and Answers

What effect does a low temperature have on metabolism in microorganisms?

  • Decreases production of unsaturated fatty acids
  • Increases production of saturated fatty acids
  • Inhibits all metabolic functions
  • Produces more unsaturated and short-chain fatty acids (correct)
  • Which of the following can be considered a hurdle for microbial growth?

  • Low pH (correct)
  • High humidity
  • High protein content
  • Low light
  • Which type of microorganisms is associated with spoilage in seafood from warm waters?

  • Lactobacillus spp.
  • Salmonella spp.
  • Micrococcus spp. (correct)
  • Pseudomonas spp.
  • In the context of food spoilage, what action does pectinase perform?

    <p>Decomposes polysaccharides in fruits</p> Signup and view all the answers

    What characteristic does lactic acid bacteria have when found in unpasteurized milk?

    <p>They are useful for fermentation</p> Signup and view all the answers

    Which of the following microorganisms is primarily responsible for the sour odor in milk?

    <p>Lactobacillus</p> Signup and view all the answers

    What is a primary source of microbial flora in food during handling?

    <p>Contamination from equipment</p> Signup and view all the answers

    Which of the following is a characteristic of spoilage organisms in muscle foods?

    <p>They include psychrotrophic aerobes</p> Signup and view all the answers

    Which of the following statements accurately describes bacteria?

    <p>They are unicellular and can be found everywhere.</p> Signup and view all the answers

    What is the optimal pH range for the growth of most bacteria?

    <p>6.5-7.5</p> Signup and view all the answers

    What factor most significantly affects the microbial growth of bacteria?

    <p>Nutrient availability</p> Signup and view all the answers

    Which group of microorganisms can survive in very low pH environments?

    <p>Molds</p> Signup and view all the answers

    Which type of microorganism requires a specific low level of oxygen for growth?

    <p>Microaerophilic</p> Signup and view all the answers

    At what temperature range do psychrophiles thrive?

    <p>10-15C</p> Signup and view all the answers

    What is the primary consequence of low water activity for bacterial survival?

    <p>Death due to insufficient water</p> Signup and view all the answers

    Which classification of bacteria survives best at temperatures around 30-37C?

    <p>Mesophiles</p> Signup and view all the answers

    What compound is produced from lysine during protein degradation?

    <p>Cadaverine</p> Signup and view all the answers

    Which microorganism is utilized in the fermentation of yogurt?

    <p>Lactobacillus delbrueckii</p> Signup and view all the answers

    What is the primary end product of cereal grain fermentation during beer production?

    <p>Ethanol and carbon dioxide</p> Signup and view all the answers

    At what temperature and duration is whole milk heated during yogurt preparation?

    <p>85C for 30 minutes</p> Signup and view all the answers

    Which enzyme is added to milk to facilitate rennet coagulation in cheese making?

    <p>Chymosin</p> Signup and view all the answers

    What role does pH play in the fermentation process mentioned in the content?

    <p>It helps lower the pH to create a more acidic environment</p> Signup and view all the answers

    Which of the following statements about Clostridium laramie is true?

    <p>It contributes to sour odors in spoiled meat</p> Signup and view all the answers

    What happens to proteins when they are spoiled anaerobically by microorganisms like Pseudomonas and Acinetobacter?

    <p>They produce foul-smelling compounds</p> Signup and view all the answers

    Study Notes

    Microorganisms

    • Small living entities (bacteria, viruses, protozoa, fungi)
    • Utilize organic matter to form inorganic compounds
    • Eukaryotes (true nucleus) vs. prokaryotes (no true nucleus)
    • Scientific names use genus and species names
    • Example: Escherichia coli

    Bacteria

    • Unicellular organisms
    • Size: 1 μm in length
    • Ubiquitous (found everywhere)
    • Classified by crystal violet retention (Gram-positive or Gram-negative)
    • Different shapes (cocci, bacilli, spirilla)
    • Sporulation: response to unfavorable conditions

    Factors Affecting Microbial Growth

    • Nutrients: Chemotrophic (lithotrophic or organotrophic) vs. phototrophic
    • Water activity (aw): Measure of unbound water availability; bacteria require higher aw than other organisms (>0.9).
    • Acidity/Alkalinity (pH): Optimal growth ranges vary by organism (e.g., bacteria 4.5-9.0, optimal 6.5-7.5; yeasts 3.0-8.5, optimal 4.0-6.5; molds 2.0-11.0, optimal 4.5-6.8)

    Sources of Microorganisms

    • Air, soil, water, surfaces
    • Human colon
    • Food: raw materials, handling, processing, storage
    • Categorized as spoilage, pathogenic, or useful microorganisms

    Muscle Foods (e.g. beef, pork, seafood)

    • Microbial sources of spoilage
      • Psychrotrophic aerobes
      • Salmonella, Vibrio, and Aeromonas (pathogens in specific types)

    Fruits and Vegetables

    • Spoilage from acid-tolerant, or spore-forming microorganisms (e.g., Bacillus, Clostridium, Lactobacillus, Leuconostoc)

    Dairy

    • Lactic acid bacteria are important (found in unpasteurized milk)
    • Pathogens like Mycobacterium, Coxiella, Listeria, Pseudomonas can cause problems during processing

    Food Spoilage (Carbohydrates & Proteins)

    • Carbohydrate spoilage: use of pectinase, cellulase, etc.
    • Protein spoilage: breakdown to amino acids, foul-smelling compounds

    Microbial Fermentation

    • Milk fermentation (cheese, yogurt) uses bacteria and enzymes for different results
    • Cereal grain fermentation (beer): uses yeast and enzymes to produce ethanol.

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    Description

    Test your knowledge about microorganisms, including bacteria, fungi, and viruses. This quiz covers their characteristics, classification, and the factors that affect their growth. Challenge yourself to identify different types and understand their ecological significance.

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