Microtubule

A hollow cytoskeletal tube built from tubulin proteins. Microtubules organize cell interiors, form the mitotic spindle, and provide structural cores for cilia and flagella.

Tubulin: A protein family whose α- and β-subunits assemble into microtubule walls. Alternating α- and β-tubulin subunits form the microtubule’s repeating building blocks.
Mitotic spindle: A microtubule-based structure that separates duplicated chromosomes during cell division. Spindle microtubules attach to chromosomes and help distribute them to daughter cells.
Alpha-tubulin: A tubulin protein that pairs with β-tubulin to form the basic microtubule building block. α-tubulin occupies one side of each tubulin heterodimer in the microtubule wall.
Intermediate filament: A durable cytoskeletal filament that resists mechanical stress and lacks the polarity of microtubules. Intermediate filaments provide tensile strength rather than polarized tracks for motors.
Dynamic instability: The stochastic switching of microtubules between growth and rapid shrinkage. Changing between growth and shrinkage lets microtubules explore cellular space.
Kinetochore: A protein structure assembled on a chromosome’s centromere that binds spindle microtubules. Kinetochore attachments connect chromosomes to microtubules during segregation.
Beta-tubulin: A tubulin protein that pairs with α-tubulin and binds exchangeable GTP. β-tubulin’s nucleotide state helps regulate microtubule growth and stability.
Microfilament: A thin cytoskeletal filament composed primarily of actin. Microfilaments are narrower than microtubules and support different forms of movement.
Microtubule polarity: The structural distinction between a microtubule’s rapidly growing plus end and its minus end. Polarity directs assembly and determines how motor proteins travel along the tube.
Axoneme: The microtubule-based internal framework of eukaryotic cilia and flagella. Its organized microtubules support the beating of motile cilia and flagella.

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