Axoneme

Axoneme is a microtubule structure found in flagella and cilia, which are hair-like structures present on the surface of many eukaryotic cells. The axoneme serves as the "skeleton" of these structures, providing both support and mobility.

Structure

The axoneme is composed of a ring of nine doublet microtubules surrounding a central pair of single microtubules. This arrangement is often referred to as the "9+2" structure. Each doublet microtubule is composed of an A tubule and a B tubule. The A tubule has 13 protofilaments, while the B tubule has 10. The central pair of microtubules are stabilized by radial spokes, which connect them to the surrounding doublets.

Function

The axoneme is responsible for the movement of cilia and flagella. This movement is powered by dynein, a motor protein that uses the energy from ATP hydrolysis to "walk" along the microtubules. The coordinated movement of dynein molecules along the axoneme causes the cilia or flagella to bend and move.

Clinical significance

Defects in the axoneme structure can lead to a variety of medical conditions, collectively known as ciliopathies. These include primary ciliary dyskinesia, a condition characterized by chronic respiratory infections, infertility, and situs inversus (a reversal of the normal asymmetry of the body organs).

See also

• Microtubule
• Cilia
• Flagella
• Ciliopathies