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BIOS 242 Final Exam Guide, Review Questions, Question Bank / BIOS242 Final Exam Guide (Latest-2021): Microbiology: Chamberlain College Of Nursing $15.49
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BIOS 242 Final Exam Guide and Review Questions
Chapter 1:
1. Compare the scientists’ beliefs and experiments for spontaneous generation.
Aristotle:
- proposed spontaneous generation: living things can arise from nonliving matter.
Redi:
- When decaying meat was kept isolate from flies, maggots never developed. Meat
exposed to flies was soon infested. Scientist’s began to doubt Aristotle’s theory.
Needham:
- Scientists didn’t believe that animals could arise spontaneously, but that microbes could.
Neeham’s experiments with beef gravy and infusions of plant material reinforced this
idea.
Spallanzi:
- Results contracted Needham’s findings. Concluded that: Needham failed to heat vials
sufficiently to kill all microbes or had not sealed vials tightly enough. Microorganisms
exist in air and can contaminate experiments. Spontaneous generation of microorganisms
does not occur. The debate continued until the experiments conducted by Louis Pasteur.
Pasteur:
- Performed investigations of spontaneous generation. When the “swan-necked” flasks
remained upright, no microbial growth appeared. When the flask was tilted, dust from the
bend in the neck seeped back into the flask and made the infusion cloudy with microbes
within a day.
2. What were the scientists/physicians Leeuwenhoek, Snow, and Lister known for?
3. What are the major groups of microorganisms, and are they prokaryotic, eukaryotic, or
acellular?
Bacteria and Archaea: prokaryotic (lack nuclei)
Fungi: eukaryotic (have membrane-bound nucleus)
Protozoa: single-celled eukaryotes
Algae: unicellular or multicellular
4. Describe the steps in the scientific method.
Scientific method:
- Observation leads to question
- Question generates hypothesis
- Hypothesis is tested through experiments
- Results prove or disprove hypothesis
5. Which scientist had steps to identify the etiological agent, and what are those steps?
Robert Koch: studied disease causation (etiology)
Koch’s postulates:
- Suspected causative agent must be found in every case of the disease and be absent from
healthy hosts.
- Agent must be isolated and grown outside the host.
- When agent is introduced into a healthy, susceptible host, the host must get the disease.
, - Same agent must be found in the diseased experimental host.
Chapter 3
1. How do prokaryotes differ from eukaryotes in terms of cellular structure? What is the size
difference?
Prokaryotes:
- Contains no nucleus - has DNA in nucleoid.
- 70S ribosomes: 50S and 30S.
- Haploid.
- Single celled.
Eukaryotes:
- Contains nucleus.
- Internal structures and organelles.
- Single celled or multicellular.
- 80S ribosomes: 60S and 40S
2. What are the differences in the cellular envelope of a gram + and gram – bacterium? What is
the periplasmic space?
Gram-positive:thick layer of peptidoglycan, purple when stained, susceptible to antibiotics
Gram-negative:thin layer of peptidoglycan, bilayer membrane outside and contain
phospholipids, proteins, and lipopolysaccharide (lipid A), pink when stained, resistant to
antibiotics
3. What are the effects on a cell when they are placed in a hypertonic, hypotonic, or isotonic
solution?
Hypertonic: shrink-crenation
Hypotonic: burst
Isotonic: stay the same
, 4. How is the cell membrane selectively permeable? How does this layer differ from the cell wall
in bacteria?
- The cell wall controls passage of substances into and out of the cell (active and passive
transport). It is made up of proteins and phospholipids that are hydrophilic and
hydrophobic.
- In bacteria, the cell wall provides structure, shape, and protection from osmotic forces. It
is composed out of peptidoglycan and have two types: gram-positive and gram-negative.
5. Describe the origin, structure, and function of mitochondria.
- Makes ATP, 2 membranes composed of a phospholipid bilayer, and interior matrix
contains 70S ribosomes and circular molecule of DNA.
Chapter 4
1. Compare and contrast the staining protocols for the gram stain, capsule stain, spore stain, and
the acid fast.
Gram stain: distinguishes bacteria based on cell wall (crystal-violet) (safranin).
- Gram-positive: purple - peptidoglycan is thicker, allowing color to seep in, susceptible
to antibiotics
- Gram-negative: pink - colorless in 3rd stage because peptidoglycan layer is
thinner,pariplasmic membrane, resistant to antibiotics
Capsule stain: uses a negative stain, stains the background and organism remains the same
(looks like a halo). No heat, water, or mordant.
Spore stain: uses heat to stain, stains bacterial endospores-green and red Christmas tree safranin,
malachite (green).
Acid-fast: distinguishes bacteria based on cell wall properties, uses heat to stain, and used to
identify mycobacterium (Carbolfushion and methylene blue) acid fast stain red, and non-acid fast
stain blue.
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