Cell Biology Overview and History
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Cell Biology Overview and History

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Questions and Answers

What is the role of mRNA in the process of transcription?

  • To unwind the DNA molecule
  • To carry genetic information from the nucleus to the cytoplasm (correct)
  • To encode specific proteins
  • To synthesize complementary strands of DNA

    • During translation, what forms the translational complex?

  • Free amino acids and nucleotides
  • Ribosomes and restriction enzymes
  • DNA, RNA polymerase, and ribosomes
  • mRNA, tRNA, and ribosomes (correct)

    • Which process involves cutting DNA at specific locations?

  • DNA replication
  • DNA transformation
  • DNA sequencing
  • Recombinant DNA technology (correct)

    • What does DNA cloning aim to achieve?

    <p>Generate multiple copies of a specific DNA sequence</p> Signup and view all the answers

    Which tool is primarily used in DNA sequencing to determine base sequences?

    <p>Sequencing methods</p> Signup and view all the answers

    What did Robert Hooke first observe that led him to coin the term 'cells'?

    <p>Cork under a microscope</p> Signup and view all the answers

    Which of the following limitations hindered early cell biology?

    <p>The use of single-lens microscopes</p> Signup and view all the answers

    What advancement was made by using compound microscopes in the 1830s?

    <p>Improved ability to see structures 1 µm in size</p> Signup and view all the answers

    What aspect did Robert Brown's observations with the microscope primarily focus on?

    <p>Identifying the nucleus in plant cells</p> Signup and view all the answers

    Which of the following contributed to the development of modern cell biology?

    <p>The convergence of cytology, genetics, and biochemistry</p> Signup and view all the answers

    What was the primary focus of cell biology in its early days?

    <p>Observation with little emphasis on explanation</p> Signup and view all the answers

    Which of the following structures was identified by Robert Brown using microscopy?

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

    How did Robert Hooke's observations differ from later studies in cell biology?

    <p>He observed only dead plant tissues.</p> Signup and view all the answers

    What is the main function of antibodies in fluorescence microscopy?

    <p>To bind to target molecules called antigens</p> Signup and view all the answers

    Which microscopy technique utilizes a laser beam to illuminate a specific plane of the specimen?

    <p>Confocal microscopy</p> Signup and view all the answers

    How does the limit of resolution vary between light microscopy and electron microscopy?

    <p>Electron microscopy has a limit of resolution about 100 times better than light microscopy</p> Signup and view all the answers

    What is the resolution limit for a standard light microscope?

    <p>200–350 nm</p> Signup and view all the answers

    What characteristic of brightfield microscopy affects the accuracy of living cell representation?

    <p>The preparation process can introduce distortions.</p> Signup and view all the answers

    In which microscopy technique are electrons transmitted through the specimen?

    <p>Transmission electron microscopy (TEM)</p> Signup and view all the answers

    What does the resolving power of a microscope refer to?

    <p>The ability to distinguish fine details</p> Signup and view all the answers

    Which of the following objects can be observed using light microscopy?

    <p>Eukaryotic cells</p> Signup and view all the answers

    What is a primary advantage of phase-contrast and differential interference contrast microscopy?

    <p>They allow clear visualization of living cells by enhancing light transmission.</p> Signup and view all the answers

    Which of the following statements about green fluorescent protein (GFP) is true?

    <p>GFP can be used to study live cell processes</p> Signup and view all the answers

    At what scale can ribosomes be observed?

    <p>30 nanometers</p> Signup and view all the answers

    What does scanning electron microscopy (SEM) detect?

    <p>Electrons deflected from the outer surface of a specimen</p> Signup and view all the answers

    Which aspect of microscopy is not effective for observing very small structures like proteins and DNA?

    <p>Light microscopy</p> Signup and view all the answers

    What defines the resolving power of the electron microscope compared to the light microscope?

    <p>It can observe smaller structures down to nanometers.</p> Signup and view all the answers

    Which of the following microscopy techniques does not require staining of samples?

    <p>Phase-contrast microscopy</p> Signup and view all the answers

    How does an increase in object density affect light microscopy?

    <p>It changes the phase of transmitted light, enhancing visibility.</p> Signup and view all the answers

    What is one of the key conclusions of the cell theory postulated by Schwann?

    <p>All organisms are composed of one or more cells.</p> Signup and view all the answers

    Which strand of biological inquiry focuses specifically on the chemical processes and molecular interactions within cells?

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

    Why has microscopy been crucial for cell biologists?

    <p>It aids in observing the small size of cells and their components.</p> Signup and view all the answers

    What is the size of a micrometer (µm) in standard metric units?

    <p>One millionth of a meter</p> Signup and view all the answers

    Which measurement unit would be appropriate for assessing the size of DNA molecules?

    <p>Nanometer (nm)</p> Signup and view all the answers

    What addition to the cell theory was made by Virchow in 1855?

    <p>All cells arise only from preexisting cells.</p> Signup and view all the answers

    Which of the following is true regarding the dimensions of bacterial cells compared to plant and animal cells?

    <p>Bacterial cells are a few micrometers in diameter, while plant and animal cells are 10–20 times larger.</p> Signup and view all the answers

    What is the angstrom (Å) primarily used for in cell biology?

    <p>Measuring dimensions within proteins and DNA molecules.</p> Signup and view all the answers

    Study Notes

    Cell Biology Overview

    • Cell is the basic unit of life, constantly changing
    • Modern cell biology combines cytology, genetics, and biochemistry
    • Fluorescence microscopy visualizes cell nuclei (red), microtubules (green), and cell-cell contacts (blue)

    History of Cell Theory

    • Robert Hooke (1665) first observed and named cells after compartments in cork, using a microscope
    • Early progress in cell biology was hindered by limited microscope resolution and descriptive nature of studies
    • Compound microscopes (1830s) improved magnification and resolution, allowing observation of structures as small as 1 µm

    Development of Cell Theory

    • Robert Brown discovered the nucleus within plant cells using a compound microscope
    • Matthias Schleiden concluded all plant tissues are composed of cells
    • Thomas Schwann made the same conclusion for animal tissues
    • Schwann (1839) proposed the cell theory:
      • All organisms are composed of one or more cells
      • Cells are the basic structural unit of all organisms
    • Virchow (1855) added to the cell theory:
      • All cells come from preexisting cells

    Modern Cell Biology

    • Integrates three strands of biological inquiry: cytology, biochemistry, and genetics
    • Cytology: focuses on cellular structure and uses optical techniques
    • Biochemistry: studies cellular structure and function
    • Genetics: focuses on information flow, heredity, and genome sequencing

    Cellular Dimensions

    • Micrometer (µm, micron): one millionth of a meter (10−6 m)
    • Bacterial cells are a few µm in diameter
    • Plant and animal cells are 10-20 times larger than bacteria
    • Organelles are comparable in size to bacterial cells

    Microscopy

    • Light microscopy (brightfield microscopy):
      • Earliest tool for cytologists
      • Allows identification of cellular structures like nuclei, mitochondria, and chloroplasts
      • Requires dead, fixed, and stained samples
    • Limits of Resolution:
      • The minimum distance between two objects for them to be seen as separate
      • Light microscope resolution is about 200–350 nm

    Specialized Light Microscopes

    • Phase-contrast microscopy: enhances contrast in transparent specimens
    • Differential interference contrast (DIC) microscopy: enhances contrast and creates a three-dimensional effect
    • Fluorescence microscopy: detects fluorescent proteins, DNA sequences, or molecules by binding to antibodies
      • Antibodies can be coupled to fluorescent molecules
      • Green fluorescent protein (GFP) can be used to study protein distribution
    • Confocal microscopy: uses a laser beam to illuminate a single plane of a fluorescent specimen
    • Digital video microscopy: uses video cameras to capture images

    Electron Microscopy

    • Uses a beam of electrons for higher resolution and magnification
    • Transmission electron microscopy (TEM): electrons are transmitted through the specimen
    • Scanning electron microscopy (SEM): surface of the specimen is scanned by detecting deflected electrons.
    • Electron microscope:
      • Resolution is about 100 times better than light microscopes
      • Magnification can be up to 100,000×

    Working with DNA

    • Recombinant DNA technology:
      • Uses restriction enzymes to cut DNA at specific sites
      • Creates recombinant DNA molecules from different sources
    • DNA cloning: generates multiple copies of a specific DNA sequence
    • DNA transformation: introduces DNA into cells

    Sequencing DNA

    • DNA sequencing methods determine the base sequence of DNA molecules
    • Entire genomes (all DNA content of a cell) can be sequenced

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    Description

    Explore the fundamental concepts and history of cell biology, including significant contributions from scientists like Robert Hooke, Robert Brown, Matthias Schleiden, and Thomas Schwann. This quiz covers the basic unit of life, advancements in microscopy, and the development of cell theory.

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