Cytoskeleton CSF 2

Cytoskeleton

A dynamic network of protein filaments that provides structural support, organization, and movement for the cell.

Microfilaments (Actin Filaments)

The thinnest cytoskeletal filaments, made of actin; key for cell shape and movement.

Microtubules

The thickest cytoskeletal filaments, hollow tubes made of tubulin; key for transport and cell division.

Intermediate Filaments

Ropelike filaments that provide mechanical strength; not used as transport tracks.

Actin

The globular protein monomer that polymerizes to form microfilaments.

G-actin (Globular Actin)

The soluble, monomeric form of actin.

F-actin (Filamentous Actin)

The polymeric, filamentous form of actin.

ATP (Adenosine Triphosphate)

The nucleotide that provides energy for actin polymerization and myosin movement.

ATP Binding Domain

The cleft on the actin monomer where ATP binds and is hydrolyzed.

Tubulin

The protein that forms microtubules; exists as alpha and beta tubulin.

Alpha-tubulin (α-tubulin)

One of the two subunits in a tubulin heterodimer.

Beta-tubulin (β-tubulin)

One of the two subunits in a tubulin heterodimer; binds GTP.

Heterodimer

A stable dimer of one alpha-tubulin and one beta-tubulin; the building block of microtubules.

Protofilament

A linear chain of tubulin heterodimers; 13 protofilaments form a microtubule.

GTP (Guanosine Triphosphate)

The nucleotide that provides energy for tubulin polymerization.

Plus End (+ End)

The fast-growing end of a microfilament or microtubule.

Minus End (- End)

The slow-growing end of a microfilament or microtubule.

Treadmilling

The process where a filament polymerizes at the plus end and depolymerizes at the minus end simultaneously.

Dynamic Instability

The stochastic switching of microtubules between growth and shrinkage.

Kinesin

A motor protein that walks toward the plus end of microtubules.

Dynein

A motor protein that walks toward the minus end of microtubules.

Myosin

A motor protein that walks on microfilaments (actin filaments).

Motor Heads (Motor Domains)

The part of a motor protein that binds the filament and hydrolyzes ATP.

Neck Linker

The region in kinesin that connects the motor head to the stalk and powers the step.

Catalytic Core

The part of the motor head where ATP binding and hydrolysis occur.

Active Transport

Energy-dependent, directional movement of cargo by motor proteins along cytoskeletal tracks.

Diffusion

Passive, random movement of molecules down a concentration gradient.

Ameboid Movement

A form of cell crawling driven by actin polymerization at the leading edge.

Lamellipodium

A broad, actin-based cellular projection at the leading edge of a moving cell.

Cilia

Hair-like cellular projections with a microtubule core.

Motile Cilia

Cilia that beat to move fluid or the cell; have a 9+2 microtubule arrangement.

Non-motile Cilia (Primary Cilia)

Sensory cilia that do not beat; have a 9+0 microtubule arrangement.

Flagella

Long, whip-like appendages for cell propulsion; structurally similar to motile cilia.