Microtubule Dynamics and Cell Motility

Cilia are used for cellular motility in unicellular organisms, whereas in non-motile cells, they are used to move extracellular materials and have a sensory function.

Cilia use a coordinated oar-like motion, whereas flagella exhibit a variety of patterns of motions, including asymmetrical waveforms and symmetrical propeller-like movements.

The basal body is an MTOC identical to the centriole and is responsible for forming the doublets of the axoneme.

<p>The axoneme has a 9+2 arrangement of microtubules, with 9 peripheral doublets surrounding 2 central single microtubules. The radial spoke proteins connect the central sheath to the A tubules.</p> Signup and view all the answers

<p>Intraflagellar transport involves the movement of IFT particles (protein complexes) to carry tubulin or other cargo, with kinesin transporting outward and cytoplasmic dynein transporting inward.</p> Signup and view all the answers

<p>The dynein stem is anchored to the A tubule, and the movement of cilia and flagella is due to the binding and release of dynein heads, resulting in the sliding of anchored doublets. Nexin bridges limit the movement and produce bending.</p> Signup and view all the answers

<p>The primary function of Microtubule-Organizing Centers (MTOCs) is to facilitate the initial formation (or nucleation) of a small section of the microtubule, followed by its rapid elongation.</p> Signup and view all the answers

<p>The main component of the centrosome is the two barrel-shaped centrioles surrounded by electron dense pericentriolar material (PCM), and it is the major site of microtubule initiation in animal cells.</p> Signup and view all the answers

<p>Microtubules are always assembled with the minus end associated with the centrosome, and growth occurs through the addition of tubulin dimers to the plus end.</p> Signup and view all the answers

<p>GTP is required for polymerization to occur, and it is hydrolyzed shortly after polymerization. GDP-bound tubulin lacks stability on its own and will rapidly depolymerize in the absence of microtubule-associated proteins (MAPs).</p> Signup and view all the answers

<p>Dynamic instability refers to the rapid shift between growing and shrinking phases of microtubules. Plus-end tracking proteins (+TIPs) bind to the ends of microtubules to regulate the rate of growth or shrinkage and mediate attachment to structures.</p> Signup and view all the answers

<p>The ring of 13 γ-tubulin monomers in complex with additional proteins at the site of nucleation is involved in the nucleation of microtubules.</p> Signup and view all the answers