Monomers are lost when concentration of G-actin is below its critical concentration. Monomers are gained when concentration of G-actin is above its critical concentration. If it is in between the critical concentrations, the actin filaments will undergo treadmilling, which is the addition of monomers on the (+) end and loss of monomers on the (–) end.

The cytoskeleton is important for cell support and movement. It is composed of microfilaments made of actin, microtubules made of tubulin, intermediate filaments that bear tension, and cilia/flagella which are made of microtubules (tubulin).

The only choice that consists of actin microfilaments is microvilli. These motile structures are composed of cross-linked actin microfilaments. Cilia and flagella are composed of a "9+2" organization of microtubule doublets and singlets (nine doublets surrounding two singlets).

Arp2/3 is a large protein complex that is specifically responsible for aiding in the organization of the actin microfilament cytoskeleton. In particular, it helps nucleate branch points from already formed actin microfilaments. Arp2/3 is not involved in the branching of microtubules, intermediate filaments, or glycogen.

Eukaryotic flagella are primarily made up of microtubule doublets and singlets organized in a "9+2" manner (two singlets surrounded by nine doublets). Actin microfilaments are not present in flagella.

The contractile ring formed during cytokinesis consists of actin and myosin, and helps separate the two daughter cells to conclude mitosis. Sarcomeres consist of actin and myosin overlaps that are crucial to muscle contraction. Adherens junctions are specialized cell junctions that use the actin cytoskeleton to anchor adjacent cells.

Desmosomes are specialized cell junctions that are important in anchoring certain cell types to one another. Intermediate filaments are used to stabilize these connections by interacting with cadherins. Cadherins are transmembrane proteins that interact with cadherins of adjacent cells on the exoplasmic face of the plasma membrane. Adherens junctions have similar function,s but make use of actin and integrins/cadherins. 

Intermediate filaments are a component of the cytoskeleton that do not display treadmilling. Both actin microfilaments and microtubules undergo treadmilling, during which the structure is built on one end and deconstructed at the other. The result is an apparently "moving" structure with a forward and reverse end. Intermediate filaments are nor polarized and have no distinct ends, making them incapable of this action.

Actin microfilaments and microtubules also maintain gradients of ADP/ATP or GDP/GTP bound monomers respectively, used to indicate their polarity, while intermediate filaments do not. The mitotic spindle is made of microtubules.

Desmosomes, however, are specialized cell junctions that use the intermediate filament cytoskeleton to anchor adjacent cells. Membrane proteins called cadherins bind to the filaments on the intracellular surface of the membrane and bind to the extracellular regions of membrane proteins on the adjacent cell. The result is two intermediate filaments, linked by the bound proteins, to form a junction.

Mucus begins to accumulate in the lungs because the cilia no longer move. Cilia function in pushing mucus up the respiratory tract so that it doesn't build up in the lungs. When they become non-motile, they lose this capability.

The cytoskeleton is comprised of actin filaments, intermediate filaments, and microtubules.

Spindle complexes are found within cells undergoing mitosis; they are made of microtubules, but are not a fundamental part of the cytoskeleton. Cilia and flagella are also largely composed of microtubules; however, these structures are also not fundamental components of the cytoskeleton. Myosin filaments work in coordination with actin filaments during muscle contraction, but are not involved in the cytoskeleton.

Microtubules are found in various structures that promote cell motility. The axoneme is the name given to the cytoskeletal core that makes up whip-like appendages in eukaryotic cells. Axonemes display a "9+2" organization of microtubules.

Microtubules are also important in vesicle trafficking and utilize motor proteins like dynein and kinesin to accomplish this. Actin filaments use the motor protein myosin. The GDP/GTP gradient helps control microtubule treadmilling, while the ADP/ATP gradient helps control actin treadmilling. The contractile ring formed during cytokinesis consists of actin and myosin rather than microtubules.