Biology: Cells and Cellular Structure
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Questions and Answers

What is the fundamental unit of life in biology?

  • Molecule
  • Cell (correct)
  • Tissue
  • Organ

    • What type of cells are involved in moving your eyes as you read this sentence?

  • Muscle cells (correct)
  • Nerve cells
  • Blood cells
  • Epithelial cells

    • What is the function of nerve cells in the process of reading?

  • Translating words into signals (correct)
  • Storing memories
  • Contracting muscle cells
  • Regulating body temperature

    • What is the level of organization that consists of many specialized cells that could not survive on their own?

    <p>Multicellular organism</p> Signup and view all the answers

    What is the characteristic shared by all cells?

    <p>They are all related by their descent from earlier cells</p> Signup and view all the answers

    What is the term for the process of cells becoming more specialized and complex over time?

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

    What is the type of organism that exists as a single cell?

    <p>Unicellular organism</p> Signup and view all the answers

    What is the purpose of studying the cell and its components?

    <p>To understand the basic unit of life and its role in biological systems</p> Signup and view all the answers

    When was the microscope invented?

    <p>1590</p> Signup and view all the answers

    Who first saw cell walls using a microscope?

    <p>Robert Hooke</p> Signup and view all the answers

    What is the primary function of lenses in a light microscope?

    <p>To refract the light</p> Signup and view all the answers

    What is the term for the ratio of an object's image size to its real size?

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

    Up to what magnification can light microscopes effectively magnify?

    <p>1,000 times</p> Signup and view all the answers

    What is the term for the minimum distance two points can be separated and still be distinguished as separate points?

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

    What is the main limitation of a light microscope in resolving detail?

    <p>Wavelength of light used</p> Signup and view all the answers

    What type of microscopes are commonly used by scientists, including Renaissance scientists?

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

    What is the purpose of staining or labeling cell components in microscopy?

    <p>To enhance contrast</p> Signup and view all the answers

    What is the main difference between a light microscope and an electron microscope?

    <p>Beam of light or electrons used</p> Signup and view all the answers

    What is the term for the clarity of the image in a microscope?

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

    What is the theoretical resolution limit of a modern electron microscope?

    <p>0.002 nanometers</p> Signup and view all the answers

    What is the main advantage of an electron microscope over a light microscope?

    <p>Improved resolution</p> Signup and view all the answers

    What is the primary use of a scanning electron microscope (SEM)?

    <p>Analyzing cell surface topography</p> Signup and view all the answers

    What is the advantage of the super-resolution technique shown in the image?

    <p>It can break the resolution limit of standard light microscopy</p> Signup and view all the answers

    What does the deconvolution software do?

    <p>It digitally removes out-of-focus light and reassigns it to its source</p> Signup and view all the answers

    What is the function of cilia as shown in the SEM micrograph?

    <p>They are cell projections that move substances along the surface of the trachea</p> Signup and view all the answers

    What type of micrograph shows a 3-D image of the surface of a specimen?

    <p>Scanning Electron Micrograph (SEM)</p> Signup and view all the answers

    What is the advantage of using electron microscopy over light microscopy?

    <p>It has a higher resolution than light microscopy</p> Signup and view all the answers

    What is the purpose of staining or labeling cell components in microscopy?

    <p>To distinguish between different cell components</p> Signup and view all the answers

    What type of microscopy is used to profile a thin section of a specimen?

    <p>Transmission Electron Microscopy (TEM)</p> Signup and view all the answers

    What is the typical diameter of the vesicles shown in the confocal image?

    <p>40 nm</p> Signup and view all the answers

    What is the primary purpose of staining in brightfield microscopy?

    <p>To enhance contrast in the image</p> Signup and view all the answers

    What is the main advantage of phase-contrast microscopy over brightfield microscopy?

    <p>It can be used to examine living cells</p> Signup and view all the answers

    What is the principle behind fluorescence microscopy?

    <p>Fluorescent dyes absorb ultraviolet radiation and emit visible light</p> Signup and view all the answers

    What is the main difference between a standard fluorescence micrograph and a confocal image?

    <p>The presence of out-of-focus light in the image</p> Signup and view all the answers

    What is the advantage of using deconvolution in microscopy?

    <p>It creates a sharper image from a compilation of standard fluorescence micrographs</p> Signup and view all the answers

    Which type of microscopy is particularly useful for examining living, unpigmented cells?

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

    What is the purpose of using fluorescent dyes or antibodies in microscopy?

    <p>To reveal the locations of specific molecules</p> Signup and view all the answers

    Which type of microscopy produces an image that appears almost 3-D?

    <p>Differential interference contrast microscopy</p> Signup and view all the answers

    What is the main purpose of coating a specimen with a thin film of gold in a scanning electron microscope?

    <p>To enable the detection of secondary electrons</p> Signup and view all the answers

    What is the primary difference between a scanning electron microscope and a transmission electron microscope?

    <p>The way the electron beam interacts with the specimen</p> Signup and view all the answers

    Why are electromagnets used as lenses in electron microscopes?

    <p>To bend the paths of the electrons</p> Signup and view all the answers

    What is a disadvantage of electron microscopy?

    <p>The methods used to prepare the specimen kill the cells</p> Signup and view all the answers

    Why is staining or labeling cell components used in microscopy?

    <p>To enable the detection of specific cell components</p> Signup and view all the answers

    What is the advantage of the scanning electron microscope over the transmission electron microscope?

    <p>Ability to study the surface topography of the specimen</p> Signup and view all the answers

    What is a recent advancement in light microscopy?

    <p>The revitalization of light microscopy through technical advances</p> Signup and view all the answers

    What is a limitation of specimen preparation for microscopy?

    <p>It can introduce artifacts into the image</p> Signup and view all the answers

    What is the primary advantage of super-resolution microscopy?

    <p>It enables researchers to distinguish subcellular structures as small as 10-20 nm across.</p> Signup and view all the answers

    What is the main purpose of cell fractionation?

    <p>To prepare specific cell components in bulk and identify their functions.</p> Signup and view all the answers

    What is the role of the centrifuge in cell fractionation?

    <p>It spins test tubes holding mixtures of disrupted cells at a series of increasing speeds.</p> Signup and view all the answers

    What is the relationship between cytology and biochemistry?

    <p>Cytology is the study of cell structure, while biochemistry is the study of the chemical processes of cells.</p> Signup and view all the answers

    What did researchers discover about mitochondria using cell fractionation and biochemical tests?

    <p>They are involved in cellular respiration.</p> Signup and view all the answers

    What is the benefit of using fluorescent markers in microscopy?

    <p>It enables researchers to see cell structures with increasing detail.</p> Signup and view all the answers

    What is the significance of confocal microscopy?

    <p>It enables researchers to produce sharper images of three-dimensional tissues and cells.</p> Signup and view all the answers

    What is the importance of microscopes in the study of cell structure?

    <p>They are the most important tools of cytology.</p> Signup and view all the answers

    What is the primary difference between prokaryotic and eukaryotic cells with regard to their DNA?

    <p>The location of their DNA</p> Signup and view all the answers

    What is the function of the ribosomes in cells?

    <p>To make proteins according to instructions from the genes</p> Signup and view all the answers

    What is the term for the semifluid, jellylike substance inside cells where subcellular components are suspended?

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

    What is the general term for organisms that consist of eukaryotic cells?

    <p>Fungi, animals, and plants</p> Signup and view all the answers

    What is the purpose of the plasma membrane in cells?

    <p>To serve as a selective barrier</p> Signup and view all the answers

    What is the characteristic shared by all cells?

    <p>Being bounded by a selective barrier</p> Signup and view all the answers

    Study Notes

    The Fundamental Units of Life: Cells

    • Cells are the basic units of life, similar to atoms in chemistry, and are essential to understanding biological systems.
    • Many different types of cells work together in an organism, each with unique functions, such as muscle cells that help move eyes and nerve cells that transmit signals to the brain.

    Cellular Structure and Function

    • Cells are the simplest units of matter that can be considered living entities, and all organisms are composed of cells.
    • Single-celled organisms, such as Paramecium, exist, while larger organisms are multicellular, consisting of many specialized cells that work together.

    Evolutionary History of Cells

    • All cells share a common ancestry, having descended from earlier cells.
    • Over time, cells have evolved and diversified into different types, despite sharing common features.

    Cellular Components and Organization

    • Cells are organized into higher levels, such as tissues and organs, but remain the basic unit of structure and function in an organism.
    • The cell's components and functions will be explored in this chapter.

    Microscopy

    • Biologists use microscopes to study cells, which are too small to be seen by the unaided eye.
    • Microscopes were invented in 1590 and further refined during the 1600s.
    • Cell walls were first seen by Robert Hooke in 1665 using a microscope.
    • Antoni van Leeuwenhoek was able to visualize living cells using his crafted lenses.
    • Light microscopes (LM) use visible light passed through the specimen and then through glass lenses to magnify the image.
    • Three important parameters in microscopy are magnification, resolution, and contrast.
    • Magnification is the ratio of an object's image size to its real size, up to 1,000 times the actual size of the specimen.
    • Resolution is a measure of the clarity of the image, with a minimum distance of 0.2 micrometer (µm) or 200 nanometers (nm) for light microscopes.
    • Contrast is the difference in brightness between the light and dark areas of an image, and can be enhanced through staining or labeling cell components.

    Electron Microscopy

    • The electron microscope (EM) was introduced to biology in the 1950s to study organelles in eukaryotic cells.
    • Electron microscopes focus a beam of electrons through the specimen or onto its surface.
    • The resolution of electron microscopes is inversely related to the wavelength of the electrons used, achieving a theoretical resolution of about 0.002 nm.
    • In practice, electron microscopes can resolve structures as small as 2 nm across, a 100-fold improvement over standard light microscopes.
    • The scanning electron microscope (SEM) is especially useful for detailed study of the topography of cells.

    Light Microscopy

    • Brightfield microscopy: light passes directly through the specimen, but image has little contrast unless the cell is naturally pigmented or artificially stained.
    • Staining with dyes enhances contrast, but most staining procedures require cell fixation, which kills the cells.
    • Phase-contrast microscopy: variations in density within the specimen are amplified to enhance contrast in unstained cells.
    • Differential interference contrast (Nomarski): optical modifications are used to exaggerate differences in density, creating a 3-D image.
    • Fluorescence microscopy: specific molecules in the cell are revealed by labeling with fluorescent dyes or antibodies; fluorescent substances absorb ultraviolet radiation and emit visible light.

    Confocal and Deconvolution Microscopy

    • Confocal microscopy: uses a laser to eliminate out-of-focus light, creating a single plane of fluorescence in the image.
    • Deconvolution: digitally removes out-of-focus light and reassigns it to its source, creating a sharper 3-D image.

    Super-Resolution Microscopy

    • Super-resolution microscopy: uses sophisticated equipment to light up individual fluorescent molecules and record their position, allowing for resolution beyond the 200-nm limit.

    Electron Microscopy

    • Scanning electron microscopy (SEM): produces 3-D images of the surface of a specimen.
    • Transmission electron microscopy (TEM): profiles a thin section of a specimen, revealing its internal structure.

    Electron Microscopy

    • Scanning Electron Microscope (SEM) is used for detailed study of specimen topography, producing a 3D image of the surface.
    • SEM operates by scanning the surface of a gold-coated sample with an electron beam, which excites electrons that are detected and translated into an electronic signal.
    • Transmission Electron Microscope (TEM) is used to study internal structure of cells by aiming an electron beam through a thin section of the specimen.
    • TEM uses heavy metal atoms to stain certain cellular structures, enhancing electron density and producing an image displaying the pattern of transmitted electrons.

    Electron Microscopy vs. Light Microscopy

    • Electron microscopes have revealed many subcellular structures that were impossible to resolve with light microscopy.
    • However, light microscopy offers advantages in studying living cells.
    • Electron microscopy requires specimen preparation methods that kill the cells, whereas light microscopy allows for observation of living cells.

    Advances in Light Microscopy

    • Labeling individual cellular molecules or structures with fluorescent markers has made it possible to see structures with increasing detail.
    • Confocal and deconvolution microscopy have produced sharper images of three-dimensional tissues and cells.
    • Super-resolution microscopy has enabled researchers to distinguish subcellular structures as small as 10-20 nm across.

    Cell Fractionation

    • Cell fractionation is a technique used to study cell structure and function by separating major organelles and subcellular structures from one another.
    • The centrifuge is used to spin test tubes holding mixtures of disrupted cells at increasing speeds, causing cell components to settle to the bottom of the tube.
    • Cell fractionation enables researchers to prepare specific cell components in bulk and identify their functions, correlating cell function with structure.

    Integration of Cytology and Biochemistry

    • Cytology is the study of cell structure, while biochemistry is the study of the chemical processes (metabolism) of cells.
    • Understanding cell function requires the integration of cytology and biochemistry.
    • Cell fractionation and electron microscopy have helped biologists determine the functions of specific cell components, such as mitochondria being the sites of cellular respiration.

    Cell Structure and Function

    • Cells are the basic structural and functional units of every organism.
    • There are two distinct types of cells: prokaryotic and eukaryotic.

    Characteristics of Cells

    • All cells are bounded by a selective barrier called the plasma membrane (or cell membrane).
    • Cells contain a semifluid, jellylike substance called cytosol, where subcellular components are suspended.
    • All cells have chromosomes, which carry genes in the form of DNA.
    • Cells have ribosomes, which make proteins according to instructions from the genes.

    Comparison of Prokaryotic and Eukaryotic Cells

    • A major difference between prokaryotic and eukaryotic cells is the location of their DNA.
    • In eukaryotic cells, most of the DNA is in the nucleus, which is bounded by a double membrane.
    • In prokaryotic cells, the DNA is concentrated in a region called the nucleoid, which is not membrane-enclosed.

    Organisms and Their Cell Types

    • Organisms of the domains Bacteria and Archaea consist of prokaryotic cells.
    • Protists, fungi, animals, and plants all consist of eukaryotic cells.
    • Protists are a diverse group of mostly unicellular eukaryotes.

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    Learn about the fundamental units of life, cells, and their unique functions and structures in organisms.

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