A microtubule is structured as a hollow tube composed of stacks of rings, where each ring is made of $${}13$$ polymerized dimers of alpha-tubulin and beta-tubulin.

Microtubule Structure

Microtubules act as cellular tracks along which motor proteins, such as dynein and kinesin, move to transport organelles and vesicles throughout the cytoplasm.

Intracellular Transport via Microtubules

Eukaryotic cilia and flagella are cell appendages that are structurally composed of microtubules, which make up both their filament and basal body components.

Eukaryotic Cilia and Flagella

The mitotic spindle is a eukaryotic cell division structure that serves to separate chromosomes during mitosis and meiosis. It is produced by two centrosomes located at opposite ends of the cell.

Mitotic Spindle

Centrosomes are cell structures that function as microtubule-organizing centers. During eukaryotic cell division, two centrosomes position themselves at opposite ends of the cell to produce the mitotic spindle.

Centrosomes

A centriole is a cylindrical cellular structure composed of twenty-seven parallel microtubules arranged in nine triplets. A pair of centrioles positioned at right angles to each other forms a centrosome.

Centrioles

Microtubules are dynamic eukaryotic cytoskeletal structures composed of tubulin dimers (alpha-tubulin and beta-tubulin) that form hollow tubes with a diameter of $${}23\text{ nm}$$. They serve as internal support structures, transport tracks for organelles and vesicles, components of flagella and cilia, and form the mitotic spindle during cell division.

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In eukaryotic cells, the cytoskeleton is an internal network of fibers and tubes consisting of microfilaments, intermediate filaments, and microtubules. It provides structural support, anchors organelles, and serves as a transport network to move materials within the cell.

Eukaryotic Cytoskeleton

https://openstax.org/details/books/microbiology/

Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

Microbiology is produced through a collaborative publishing agreement between OpenStax and the American Society for Microbiology Press. The book aligns with the curriculum guidelines of the American Society for Microbiology.

OpenStax Microbiology Textbook

Microfilaments are dynamic eukaryotic cytoskeletal cables, measuring about 6 nm in diameter, composed of two intertwined strands of actin monomers that polymerize and depolymerize in response to cellular signals.

Microfilaments

Intermediate filaments are diverse, relatively permanent cytoskeletal fibers with a diameter of $${}10\text{ nm}$$ (thicker than actin but thinner than microtubules) that are composed of multiple strands of polymerized subunits and function to maintain the position of the nucleus, form the nuclear lamina, and anchor cells together in animal tissues.

Intermediate Filaments

Microtubules

Exocytosis is the process by which secretory vesicles move toward and fuse with the plasma membrane to release their contents outside the cell. Cells utilize exocytosis to eliminate waste products and to secrete chemical signals that other cells can receive.

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