Cytoskeleton & Cellular Junctions

Microfilaments

Solid rods of Actin. Responsible for the cleavage furrow during cytokinesis and muscle contraction (via myosin).

Actin (Microfilaments)

The structural protein building block of microfilaments.

Cleavage Furrow

The pinching of the cell membrane driven by an actin-myosin contractile ring during cytokinesis.

Microtubules

Hollow tubes of Tubulin. Form the mitotic spindle, cilia, and flagella. Act as tracks for motor proteins.

Tubulin

The structural protein building block of microtubules.

Microtubule Inhibitors (Colchicine/Paclitaxel)

Drugs that disrupt microtubules, causing cells to arrest in Metaphase or Anaphase since chromosomes cannot be separated.

Kinesin & Dynein

Motor proteins on microtubules. Kinesin moves vesicles toward periphery/membrane; Dynein brings things toward nucleus/center.

9+2 Arrangement

The specific structural arrangement of microtubules found ONLY in eukaryotic cilia and flagella (9 outer pairs, 2 central).

Intermediate Filaments

Rigid proteins (Keratin, Vimentin, Desmin) that provide structural integrity and anchor organelles.

Tight Junctions

Form a watertight seal between cells, preventing solutes and fluids from leaking between them (e.g., gut lining).

Gap Junctions (Connexons)

Direct tunnels connecting the cytoplasm of adjacent cells, allowing rapid exchange of ions (crucial for cardiac muscle).

Desmosomes

Spot-welds that physically bind adjacent cells tightly together by anchoring to intermediate filaments (found in skin).