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General Biology: What Is Life? Microscopy, Cells, and Macromolecules

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Termini in questo insieme (27)

  • What are the two major cell types in living organisms?
    Prokaryotic and eukaryotic cells, differing in complexity and structure but both carrying out all functions of life.
  • What is magnification in microscopy?
    Magnification = size of the image / size of the object; total magnification = ocular magnification × objective magnification.
  • How is resolution defined in microscopy?
    Resolution is the ability to distinguish two points as separate; better resolution means smaller minimum distance between points.
  • What factors affect resolution distance (RD) in microscopy?
    RD = λ / 2NA, where λ is wavelength of illumination and NA is numerical aperture of the lens.
  • What is numerical aperture (NA) and how is it calculated?
    NA = n sine α, where n is refractive index and α is half the angular aperture of the objective lens.
  • Why is immersion oil used in microscopy?
    Immersion oil has a refractive index similar to glass, reducing light bending and increasing numerical aperture and resolution.
  • What is the difference between a dissecting microscope and a compound light microscope?
    Dissecting microscopes view larger specimens at low magnification (~10×–80×); compound microscopes view cells and microorganisms at higher magnifications (~40×–1000×).
  • How do prokaryotic and eukaryotic cells differ structurally?
    Prokaryotes lack a nucleus and membrane-bound organelles; eukaryotes have a nucleus and membrane-bound organelles.
  • What are common shapes of prokaryotic cells?
    Coccus (sphere), bacillus (rod), and spirillus (spiral).
  • What is the typical size range of prokaryotic and eukaryotic cells?
    Prokaryotes: 1–10 µm; eukaryotes: 10–100 µm.
  • What are the three common methods of motility in microorganisms?
    • Flagellar movement using flagella
    • Ciliary movement using cilia
    • Amoeboid movement using pseudopodia
  • What is the operational definition of organic matter used in the burn test?
    Organic matter contains hydrocarbon bonds that burn, releasing CO2 and water, leaving inorganic ash.
  • How do you calculate the percentage of water in a biological sample?
    Water % = ((wet weight - dry weight) / wet weight) × 100%.
  • What does Benedict's test detect?
    Presence of reducing sugars, indicated by a color change from blue to red cupric oxide upon heating.
  • What does the iodine test detect?
    Presence of starch, indicated by a black-blue color change.
  • How is protein detected in a sample?
    Using Biuret's test, which produces a purple color in presence of proteins.
  • How can you test for fats and oils qualitatively?
    Place sample on unglazed paper; a permanent translucent spot indicates fats or oils.
  • How is density calculated for biological samples?
    Density = mass / volume, with volume often measured by water displacement.
  • What is field diameter in microscopy?
    The diameter of the visible area under the microscope; inversely related to magnification.
  • How does depth of focus change with magnification?
    Depth of focus decreases as magnification increases.
  • What is the significance of the constant in field diameter calculations?
    Field diameter × total magnification = constant for a given microscope, allowing calculation of field diameter at different magnifications.
  • What is the difference in image orientation between dissecting and compound microscopes?
    Dissecting microscopes show images with the same orientation as the specimen; compound microscopes invert and reverse the image.
  • What is the main function of dialysis tubing in the model cell experiment?
    To simulate a selectively permeable membrane allowing diffusion of certain molecules.
  • What is the role of the substage condenser in microscopy?
    Controls the angle and cone of light reaching the specimen, improving resolution.
  • Why is resolution more important than magnification in microscopy?
    Because magnification alone cannot reveal more detail if resolution is poor.
  • What is the typical resolving power of the human eye compared to light microscopes?
    Human eye: ~200 µm; best light microscopes: ~200 nm (1000× better).
  • How do electron microscopes achieve higher resolution than light microscopes?
    By using electron beams with much shorter wavelengths than visible light.