Questions and Answers
Which of the following is NOT equal to 1 mm? (Select all that apply)
Which of the following measurements is correctly matched with microorganisms of that size?
Which of the following statements is INCORRECT regarding prokaryotic cells?
You are observing a Gram stain of spherical-shaped microorganisms that are linked in a chain and stain purple. How would you describe these bacteria using the correct terminology for the cell shape and arrangement?
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Which structure acts like an 'invisibility cloak' and protects bacteria from being phagocytized?
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You have isolated a motile, gram-positive cell with no visible nucleus. You can safely assume that the cell...
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In the figure, which diagram of a cell wall is a gram-negative cell wall?
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Where are phospholipids most likely found in a prokaryotic cell?
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The DNA found in most bacterial cells...
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Which statement regarding the structure or function of ribosomes is correct?
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What would you expect to see as you look through the microscope of the Gram stain from Shelly's culture, which confirmed it is Streptococcus pyogenes?
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How will the prescribed penicillin kill S. pyogenes that is causing Shelly's infection?
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What effect will the penicillin have on Shelly's cells?
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Study Notes
Measurement and Sizes
- 1 mm equals:
- 10^-3 meters
- 100 micrometers
- 0.1 centimeters
- 1,000 nanometers (1 μm = 10^-6 m, so 1 mm = 1,000 μm)
Microorganism Sizes
- Average size for bacteria: 2 micrometers
- Common misconception: Viruses are larger than bacteria, but they typically range from 20 nanometers (nm) to 300 nm, not 10 micrometers or 1 centimeter.
Prokaryotic Cells Characteristics
- Prokaryotic cells' features:
- Circular chromosome
- Lack of membrane-enclosed organelles
- DNA not enclosed in a membrane
- Reproduce via binary fission
- Incorrect statement: Prokaryotic cells do have a plasma membrane.
Gram Staining
- Spherical-shaped microorganisms in chains that stain purple:
- Identified as gram-positive streptococci.
- Gram stain classification helps in bacterial identification.
Bacterial Structures
- The capsule serves as an "invisibility cloak," protecting bacteria from phagocytosis.
- Structures such as slime layers, fimbriae, and cell walls each have specific functions but do not serve the same protective role as capsules.
Cell Properties
- A motile, gram-positive cell without a visible nucleus:
- Confirmed to have a cell wall.
- Typically does not possess cilia or mitochondria.
Cell Wall Characteristics
- Identification of gram-negative vs. gram-positive cell walls is crucial for understanding antibiotic susceptibility.
Phospholipids Location
- Found in the plasma membrane of prokaryotic cells, crucial for maintaining the structure and function of the cell membrane.
Bacterial DNA
- Most bacterial cells contain circular DNA, not surrounded by a nuclear membrane, and typically exist in single copies.
Ribosome Structure
- In eukaryotic cells, ribosomes in mitochondria and chloroplasts are similar to prokaryotic ribosomes (70S).
- Ribosomes are responsible for protein synthesis, both free-floating and attached to the endoplasmic reticulum.
Streptococcus pyogenes
- A gram-positive organism identified via Gram staining will appear as purple spherical organisms in chain formations.
Penicillin Mechanism
- Penicillin disrupts peptidoglycan synthesis, affecting the bacterial cell wall and leading to cell lysis.
- It specifically targets bacteria without impacting human cells, as humans lack peptidoglycan.
Impact on Human Cells
- Penicillin has no effect on human cells because it specifically targets bacterial structures, such as peptidoglycan in cell walls, which are absent in eukaryotic cells.
Studying That Suits You
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Description
Test your knowledge with these flashcards focused on measurements and sizes of microorganisms. Challenge yourself to differentiate between various units of measurement and correctly match them with relevant microorganisms. Perfect for preparing for your Microbiology exam!
