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12: Cytoskeleton

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    16169

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    When a eukaryotic cell is taken out of its physiological context and placed in a plastic or glass Petri dish, it is generally seen to flatten out to some extent. On a precipice, it would behave like a Salvador Dali watch, oozing over the edge. The immediate assumption, particularly in light of the fact that the cell is known to be mostly water by mass and volume, is that the cell is simply a bag of fluid. However, the cell actually has an intricate microstructure within it, framed internally by the components of the cytoskeleton.

    • 12.1: Introduction to the Cytoskeleton
      This page discusses the structure and function of eukaryotic cells, emphasizing the cytoskeleton's role in maintaining cell shape and supporting internal organization. It describes the cytoskeleton as dynamic, facilitating transport within the cell.
    • 12.2: Intermediate Filaments
      This page discusses intermediate filaments, a protein family with six classes that provide structural support in cells. Class I keratins are found in skin, while class IV neurofilaments are important for neurons. Mutations can lead to disorders such as epidermolysis bullosa and Charcot-Marie-Tooth disease.
    • 12.3: Actin Microfilaments
      This page discusses microfilaments, or actin filaments, which are dynamic structures composed of globular actin (g-actin) that assemble into filamentous actin (f-actin) with distinct ends. These polar structures rapidly polymerize or depolymerize, allowing quick cellular responses. Their formation relies on ATP binding, and they are primarily located at the cell's periphery to interact with the environment, while in muscle cells, they play a crucial role in contraction.
    • 12.4: Microtubules
      This page discusses microtubules, which are composed of α and β tubulin subunits and require GTP for their formation. They are temperature-sensitive, disassembling at low temperatures and repolymerizing when warmed if GTP is present. Microtubules have a polarity, characterized by a less active (-) end and a more active (+) end, and they display dynamic instability due to GTP hydrolysis in β-tubulin. While strong, microtubules are less flexible than microfilaments, which can bend without breaking.
    • 12.5: Microtubule Organizing Centers
      This page discusses the dynamic structures of microtubules and microfilaments within cells. It explains that microtubules originate from the microtubule organizing center (MTOC), which is typically near the nucleus and contains centrioles and γ-tubulin, crucial for initiating microtubule growth. The page emphasizes the distinct organizational patterns of these structures and their importance in the cytoskeletal architecture across various cell types.
    • 12.6: Transport on the Cytoskeleton
      This page explains cellular transport systems, likening microtubules to railroad tracks for cargo movement and microfilaments to streets. It details the roles of kinesins and dyneins as molecular motors, specifying their directional movement in cells. The significance of axonal transport in neurons for rapid long-distance material movement is emphasized.
    • 12.7: Actin - Myosin Structures in Muscle
      This page covers the role of motor proteins like myosin II in muscle contraction via ATP hydrolysis, the structural unit of the sarcomere, and the regulation of contraction through the troponin-tropomyosin complex influenced by calcium ions. It highlights proteins such as titin, their contribution to muscle stability, and potential mutations leading to disorders.
    • 12.8: Cytoskeletal Dynamics
      This page discusses early animal development, focusing on cellular rearrangement in the blastula and the specialization of cells and tissues. It highlights neuronal motility via axon extension, emphasizing the role of the cytoskeleton, particularly actin microfilaments and microtubules. Key regulatory proteins, including profilin, thymosin β4, gelsolin, and spastin, contribute to neuronal function.
    • 12.9: Cell Motility
      This page covers cellular movement mechanisms, including ciliary and flagellar propulsion in eukaryotes and crawling on solid surfaces. It describes ciliary structure (9+2 axoneme) and its role in fluid movement, linking dysfunction to health issues like primary ciliary dyskinesia.

    Thumbnail: Image of a human cell showing microtubules in green, chromosomes (DNA) in blue, and kinetochores in pink (Public Domain; Afunguy).

    This page titled 12: Cytoskeleton is shared under a CC BY-NC-SA 3.0 license and was authored, remixed, and/or curated by E. V. Wong via source content that was edited to the style and standards of the LibreTexts platform.