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NWHSU Microbiology Cell Identification with 100% correct answers.docx, Exams of Biology

Howard Community CollegeBiology

NWHSU Microbiology Cell Identification with 100% correct answers.docx

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2024/2025

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NWHSU Microbiology Midterm
questions fully solved & updated
2025
1. Which are cellular etiologic agents of infectious disease? - answer
"Eukaryotes (fungi, parasites) and prokaryotes (bacteria)"
2. Which are a-cellular etiologic agents of infectious disease? - answer
"Viruses, virons, and prions"
3. Which groups of microorganisms are eukaryotic/prokaryotic? - answer "a)
Eukaryotic: Protista -> Plantae, fungi, animalia b) Prokaryotic: Prokaryotae
(monera)"
4. Name major differences between eukaryotic and prokaryotic cells. - answer
"a) Euk: Nucleus, nuclear envelope, more organelles, cytoskeleton (Plants and
fungi have cell walls) b) Prok: Nucleoid, cell wall, flagellum (Both have
cytoplasmic membrane, no cholesterol in prok.)"
5. What order of magnitude is the size of a bacterium? - answer 10^-6 or micro
meters
"6. What is the structure and function of glycocalyces, flagella, fimbriae, pili?"
- answer "Glycocalyx:Gelatinous sticky substance surrounding the outside of
the cell, composed of polysaccharides, polypeptides or both. 2 types exist: 1) A
capsule acts as camoflage (prevents bacteria from being recognized and
slows down phagocytosis, *virulence Factor. 2) Slime layer which is water
soluble and allows prokaryotes to attach to the surface, composes a biofilm.
Flagella: motility, not present on all bacteria. Fimbria: sticky bristle like
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NWHSU Microbiology Midterm

questions fully solved & updated

  1. Which are cellular etiologic agents of infectious disease? - answer "Eukaryotes (fungi, parasites) and prokaryotes (bacteria)"
  2. Which are a-cellular etiologic agents of infectious disease? - answer "Viruses, virons, and prions"
  3. Which groups of microorganisms are eukaryotic/prokaryotic? - answer "a) Eukaryotic: Protista -> Plantae, fungi, animalia b) Prokaryotic: Prokaryotae (monera)"
  4. Name major differences between eukaryotic and prokaryotic cells. - answer "a) Euk: Nucleus, nuclear envelope, more organelles, cytoskeleton (Plants and fungi have cell walls) b) Prok: Nucleoid, cell wall, flagellum (Both have cytoplasmic membrane, no cholesterol in prok.)"
  5. What order of magnitude is the size of a bacterium? - answer 10^-6 or micro meters "6. What is the structure and function of glycocalyces, flagella, fimbriae, pili?"
  • answer "Glycocalyx:Gelatinous sticky substance surrounding the outside of the cell, composed of polysaccharides, polypeptides or both. 2 types exist: 1) A capsule acts as camoflage (prevents bacteria from being recognized and slows down phagocytosis, *virulence Factor. 2) Slime layer which is water soluble and allows prokaryotes to attach to the surface, composes a biofilm. Flagella: motility, not present on all bacteria. Fimbria: sticky bristle like

projections, adherence to one another, host cells, and environment. Shorter than flagella. Pili: hollow tubes used for DNA transfer (Conjugation). Longer than fimbriae shorter than flagella. 1-2 per cell." a. Which of these structures are known virulence factors? - answer "Glycocalyces, flagella, fimbriae, pili" b. Which of these structures contribute to biofilm formation? - answer "Glycocalyx (slime layer), fimbrae" c. Name the various types of flagella arrangements that can be used to identify bacteria. - answer "Monotrichous, amphitrichous, lophotrichous, peritrichous" d. Which stain makes glycocalyces/capsules visible in the microscope? - answer Gram stain? e. How do spirochetes move? - answer Corkscrew motion

  1. Name the major components of a gram-positive/gram-negative cell wall. What is the appearance of gram-positive/gram-negative bacteria? - answer "Gram positive cell wall: Thick layer of peptidoglycan, containing unique polyalcohols called teichoic acids. Gram stain appearance is purple. Gram negatice cell walls: Thin layer of peptidoglycan, with an outer membrance containing proteins, and ippolysaccharides. Produce endotoxins, and appear pink with the Gram stain. The endo toxin is a lipid A molecule embeded in the outer membrane. "
  2. What is the clinical importance of the difference between gram-positive and gram-negative bacteria? - answer "Gram positive bacteria are more
  1. What are differential growth conditions? - answer Media that differentiates organisms with chemicals or certain dyes that cause organsims to product certain characteristic changes or growth patterns. a. Know the fundamental principles (pH change color change of pH indicators; visibility of certain metabolic products; specific color reactions involving certain metabolic products) - answer Notes "b. Specifically know the examples that also came up in the lab (MacConkeyƒ??s agar, fermentations in liquid culture, iron sulfide precipitate, gas bubbles, citrate as sole carbon source, indole made visible with Kovacƒ??s reagent, coagulase reaction, catalase reaction)" - answer Notes
  2. Recognize the names of methods to obtain pure cultures - answer "Obtaining pure cultures: cultures composed of cells arising from a single progenitor (progenitor is termed CFU= colony forming unit), Apsetic technique, Isolation technique=streaking"
  3. What is the best method for long-term preservation of bacterial cultures? - answer Lyophilization (decades)
  4. What is agar and what is it used for? - answer Agar is a gelatinous substance collected from plants (red sea weed) and is used as a growth medium for bacteria.
  5. Grouping of bacteria based on their ƒ??relationshipƒ?? with oxygen; what is the problem with oxygen? Name an example of a microaerophile. - answer "Obligate aerobes, obligate anareobes, faculative anaerobes, aerotolerant

anaerobes. Problem with O2 is that concentration is often variable/inconsistent??? e.g., Helicobacter pylori" "20. What are nitrogen, phosphorus, sulfur needed for in a bacterial cell? " - answer "N for anabolism and growth, P for nucleic acids, S as electron acceptor"

  1. Sketch a temperature and a pH optimum growth curve. - answer Notes "22. With respect to optimal temperature, which group do most of the human pathogens belong to?" - answer Mesophiles "23. With respect to optimal pH, which group do most of the human pathogens belong to? What about Helicobacter pylori?" - answer Neutrophiles grow best in a narrow range around a neutral pH and are pathogenic to humans. Helicobacter pylori are Neutrophiles and grow best in the mucus of the stomach where the pH is near 5 or 6. In the lab they grow best in neutral environments. Sorry guys this was wrong just watched the lecture again. Helicobacter grow best in stomach mucus
  2. Sketch a typical growth curve of a bacterial culture and name the phases. What is characteristic of each phase of growth? - answer "Phases not covered in notes? Highest growth is always at optiumum temperature (this is true, not sure if that's what's being asked)"
  3. How is microbial growth measured or a cell count assessed? What is an indirect method versus a direct method? - answer "Direct methods include serial dilution with viable plate counts, membrane filtration, and microscopic counts. Indirect methods of count involve dry weight and turbidity (A600) methods. "

competetively bind to PABA sites preventing the formation of folic acid. Rifampin blocks RNA polymerase "Found some specific examples in the text book video. Short synopsis: Cell wall, cell membrane, ribosome, docking sites, aminoacid bond formation, DNA gyrase, enzymes are competitvely bound. RNA polymerase "

  1. What are factors that have to be taken into account when choosing an antimicrobial? - answer "Environmental and human safety have to be taken into account. Harsh chemicals and extreme heat cannot be used on humans, animals and fragile objects. "
  2. What physical parameters can be used to control microbial growth? - answer "Temp., pH, osmotic pressure, filtration, radiation Cell walls with heat and freezing. heat breaks down proteins in the bacteria causing cell death. Refrigeration and freezing slowly allow ice crystals to form lysing the cells. Osmotic pressure draws water out of the cell due to high levels of sugar and salt outside of the cell membrane. Drying takes water out of the cells as well. Irradiation is used to destroy bacteria as well, the high energy beam breaks chemical bonds in the bacteria needed for growth and multiplication."
  3. List groups of chemicals that inhibit microbial growth and give examples. - answer "Table in Chapter 9 on slide 2 (antisepsis, aseptic, degerming, etc.)"
  4. What is lysozyme? - answer Human tears contain lysozyme which breaks down peptidoglycan. Lysozyme is used to reduce the number of bacteria on cheese
  5. List the 5 mechanisms by which antibiotics affect bacterial cells. - answer "1) Inhibition of cell wall synthesis 2) Inhibition of protein synthesis 3) Disruption of cytoplasmic membrane 4) Inhibition of general metabolic pathway 5) Inhibition of DNA/RNA synthesis (e.g., Penecillin)"
  1. What does broad-spectrum mean? - answer effective against many organisms
  2. List mechanisms of drug resistance. - answer 1) Produce enzyme that destroys or deactivates drug 2) Slow or prevent entry of drug into the cell 3) Alter target of drug so it binds less effectively 4) Alter the metabolic chemistry 5) Pump antimicrobial drug out of the cell before it can act 6) Biofilms retard drug diffusion and slow metabolic rate 7) Mycobacteriium tuberculosis produces MfpA protein
  3. Compare prokaryotic and eukaryotic genomes - answer "Prokaryotic: haploid(single chromosome copy), circular molecule of DNA in nucleoid. Eukaryotic: nuclear chromosome, linear, DNA associated with histones and highly compacted, eukaryotic cells are usually diploid "
  4. Contrast vertical and horizontal gene transfer - answer Horizontal: donor cell contributes part of genome to recipient cell. Verticle: organisms replicate their genomes and provide copies to descendants a. Transformation - answer Transfer of a naked DNA fragment (transformation) b. Transduction - answer Transport of bacterial DNA by bacteriophages (transduction) c. Conjugation - answer "Direct transfer between two bacteria temporarily in physical contact (conjugation),"
  1. What makes up a virus in the extracellular state? - answer Protein coat (capsid) surrounding nucleic acid. Called nucleocapsid or viroid. a. What are capsids made of? - answer Proteinaceous subunits called capsomeres b. What is are viral envelopes made of? - answer Phospholipid bilayer and proteins c. What are spikes? - answer Virally coded glycoproteins
  2. What makes up a virus in the intracellular state? - answer "No capsid, just nucleic acid"
  3. Lytic cycle vs lysogeny/latency - answer "Lytic cycle: Host cell disintegrates as consequence of viral replication. Lysogeny/latency: Host cell continues to grow and reproduce normally for generations, then lyses due to stress."
  4. Know the 5 stages of viral replication. - answer 1) Attachment 2) Entry (bacterial chromosome degraded) 3) Synthesis 4) Assembly 5) Release a. By what means can viruses attach to host cells? - answer Viral surface proteins have an affinity for the specific proteins of the host cell b. How can non-enveloped (naked) viruses enter a cell? - answer Direct penetration: They attach to receptors on the cytoplasmic membrane and the caspid releases the viral genome into the cell.

c. How can enveloped viruses enter a cell? - answer Membrane fusion or Endocytosis d. How are naked/enveloped viruses released from host cells? - answer Naked viruses are released by exocytosis or lysis a. Understand the principles of replication and what serves as mRNA as well as the template for genome replication for each type of virus (grouped by nucleic acid structure) - answer See notes Fig. 13.13... b. Be familiar with the special cases of reverse transcription and RNA replication - answer "Reverse transcription: Done by retroviruses (e.g., HIV). RNA replication: Poor proof reading and DNA repair leads to highter mutation rate." c. Know specific viruses and types of cancers they have been linked to. - answer Cancers listed in notes but not specific viruses...

  1. What type of biomolecule is a prion? How does it cause disease? - answer Proteinaceous infectious agents. Fibrils deposit into brain inducing loss of brain matter "54. In a biopsy, what is the evidence of the presence of a prion disease?" - answer Spongiform encephalopathies
  2. List commonly known animal prion diseases and their hosts. - answer "Scrapie (sheep), Bovine Spongiform Encephalopathy (cow)"
  1. What is a saprobe? - answer Fungi that consume dead biomass
  2. What three characteristics characterize protozoa? - answer "Eukaryotic, unicellular, and lack a cell wall (animal-like)"
  3. What are the two stages in a typical life cycle of protozoa? Describe the two stages. - answer "Active, feeding stage: reproductive stage in humans that causes disease. Dormant, resting stage: more reilent, often infective stage"
  4. What are the two groups of helminthes? - answer Platyhelminths (Flat worms) and Nematodes (Round worms)
  5. What is often the diagnostic stage of a helminthic infection? - answer Microscopic (eggs)
  6. Give examples of arachnid and insect vectors. Host Microbe Interaction - answer "Arachnid: Ticks and mites; Insect: Lice, fleas, flies, mosquitos, and bugs"
  7. Name and compare the three types of symbiotic relationships found between humans and microorganisms. - answer "Mutualism: both benefit. Commensalism: microorganism benefits, human neither benefits nor is harmed. Parasitism: microorganism benefits, human is harmed"
  8. List alternate terms for normal microbiota. - answer "Normal flora, Indigenous microbiota, and Microbiome"
  1. What are resident and transient microbiota? - answer "The two types of Normal Microbiota (organisms that colonize the body's surfaces without normally causing disease). Residents normally last a lifetime whereas Transient last only a short period of time (due to competion, elimination, or chemical/physical changes)."
  2. List the body systems where normal microbiota reside. - answer "Respiratory tract, digestive tract, urinary and reproductive systems, eyes and skin"
  3. What are opportunistic pathogens? - answer "A Normal Microbiota that converted into a pathogen due to an opportunity to do so (ie. introduction into an unusual body system, change in normal flora, or immune system compromised)"
  4. What are circumstances where opportunistic infections occur? - answer "Introduction into an unusual body system (E. coli causing UTI), change in normal flora (yeast infection after antibiotic treatment), or immune system compromised (HIV, cancer, steroids, diabetes)"
  5. What can serve as a reservoir for pathogens? - answer "Animal reservoirs, human carriers, and nonliving reservoirs"
  6. How can zoonoses be transmitted? - answer "Direct contact with an animal or its waste, eating animals, and/or bloodsucking arthropods"
  7. What is a human carrier? - answer "Infected individuals who are asymptomatic, but infective to others (ie. HIV or hepatitis B)"
  8. What are common nonliving reservoirs? - answer "Soil, water, or food"