Question

Microtubules are formed from the tubulin heterodimer, which is composed of the nucleotide-binding _______ protein and the _______ protein. Tubulin dimers are stacked together into protofilaments; _______ parallel protofilaments form the tubelike structure of a microtubule. _______ rings are important for microtubule nucleation and are found in the _______ , which is usually found near the cell's nucleus in cells that are not undergoing mitosis. A microtubule that is quickly growing will have a _______ cap that helps prevent the loss of subunits from its growing end. Stable microtubules are used in cilia and flagella; these microtubules are nucleated from a _______ and involve a "_______ plus two" array of microtubules. The motor protein _______ generates the bending motion in cilia; the lack of this protein can cause Kartagener's syndrome in humans.

1) α-tubulin
2) β-tubulin
3) γ-tubulin
4) Δ-tubulin
5) ATP
6) GTP
7) UTP
8) myosin
9) dynein
10) kinesin
11) centrosome
12) basal body
13) vimentin
14) nine
15) thirteen
16) twenty-one
17) four
18) two

Answer 1

Microtubules are cytoskeletal structures composed of α-tubulin and β-tubulin proteins, forming a hollow cylinder stabilized by a GTP cap.

Step-by-step explanation:

Microtubules are formed from the tubulin heterodimer, which is composed of the nucleotide-binding α-tubulin protein and the β-tubulin protein. Tubulin dimers are stacked together into protofilaments; thirteen parallel protofilaments form the tubelike structure of a microtubule. γ-tubulin rings are important for microtubule nucleation and are found in the centrosome, which is usually found near the cell's nucleus in cells that are not undergoing mitosis.

A microtubule that is quickly growing will have a GTP cap that helps prevent the loss of subunits from its growing end. Stable microtubules are used in cilia and flagella; these microtubules are nucleated from a basal body and involve a "nine plus two" array of microtubules. The motor protein dynein generates the bending motion in cilia; the lack of this protein can cause Kartagener's syndrome in humans.