Microtubules are hollow protein polymers that help shape and organize eukaryotic cells. Their dimensions, construction, and polarity explain how they can provide support and serve as directional tracks.
Microtubules are built from two globular proteins, α-tubulin and β-tubulin. One of each joins non-covalently to form an α/β heterodimer. Dimers join end-to-end into long chains called protofilaments. Protofilaments then associate side-by-side to form a hollow cylinder; its inner space is called the lumen.
All flashcards
What is a tubulin heterodimer?
A non-covalent pair made of one α-tubulin molecule and one β-tubulin molecule. These dimers are the building blocks of microtubules.
How does a microtubule form?
Tubulin heterodimers join end-to-end into protofilaments, and multiple protofilaments associate laterally to create a hollow cylinder.
What does the term lumen mean?
The lumen is the hollow inner space enclosed by the microtubule wall.
Which subunits are exposed at the two ends?
The minus end exposes α-tubulin, while the plus end exposes β-tubulin.
How many protofilaments are most common in a eukaryotic microtubule?
Thirteen protofilaments are the most common arrangement, though other numbers and lattice architectures also occur.
Quiz questions
Which two proteins form the repeating tubulin dimer in a eukaryotic microtubule?Answer: α-tubulin and β-tubulin
What is a protofilament?Answer: A linear chain of end-to-end α/β-tubulin dimers
What is the lumen of a microtubule?Answer: The hollow space inside its tubular structure
Which tubulin subunit is exposed at the plus end?Answer: β-tubulin
How does microtubule polarity support cellular function?Answer: It creates distinct ends that support directional growth and motor transport.
Based on the Wikipedia article Microtubule, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.