Cytoskeleton – Part 1: Actin and cell movement

A set of vocabulary flashcards covering actin dynamics, protrusions, motor proteins, microtubules, and intermediate filaments from the lecture notes.

Actin

Cytoskeletal protein that polymerizes to form filaments (F-actin) and drives many structural and motility functions.

F-Actin

Filamentous actin formed by polymerization of actin subunits; polar with a plus end (ATP-actin) and a minus end (ADP-actin).

Plus end

The fast-growing end of an actin filament where ATP-actin adds.

Minus end

The slower-growing end of an actin filament where ADP-actin is lost.

Stress fibre

Bundled actin filaments anchored at focal adhesions that generate contractile tension.

Focal adhesion

Complexes linking the actin cytoskeleton to the extracellular matrix via integrins.

Talin

Adaptor protein that connects integrins to actin at focal adhesions, anchoring actin to the membrane link.

Integrin

Transmembrane receptors that connect the ECM to the actin cytoskeleton at focal adhesions.

ECM

Extracellular matrix; network surrounding cells providing structure and signaling.

Tropomyosin

Coiled-coil protein that binds along actin filaments, stabilizing them (and regulating access of myosin in muscle).

Capping protein

Protein that terminates actin filament growth by capping the barbed end.

Actin cortex

Dense actin network beneath the plasma membrane that stabilizes the membrane and anchors the mesh.

Microvilli

Long, finger-like membrane protrusions that increase surface area.

Pseudopodia

Transient membrane extensions that probe the environment and aid in migration or phagocytosis.

Lamellipodia

Broad, sheet-like actin protrusions that drive cell migration.

Filopodia

Thin, actin-rich protrusions that explore the surroundings during movement.

Myosin

ATP-powered motor protein that moves along actin filaments to generate contractile force.

Sarcomere

The contractile unit of a muscle, where actin and myosin slide past each other to shorten the fiber.

Troponin

Ca2+-binding protein that moves tropomyosin to expose myosin-binding sites on actin in muscle contraction.

Calcium (Ca2+)

Ion that triggers contraction by causing troponin to shift tropomyosin away from myosin-binding sites.

Cytokinesis (actin/myosin ring)

Division of a cell driven by contraction of an actin–myosin ring at the equator.

Microtubules

Hollow tubes made of tubulin with plus and minus ends; dynamic, organizing the cell interior.

Alpha/beta-tubulin

Tubulin dimers that polymerize to form microtubules.

MTOC/Centrosome

Microtubule organizing center; anchors minus ends and nucleates microtubule growth.

Kinesin

Plus-end–directed microtubule motor protein that transports cargo toward the cell periphery.

Dynein

Minus-end–directed microtubule motor protein that moves cargo toward the cell center.

Mitotic spindle

Microtubule-based structure that segregates chromosomes during mitosis.

Intermediate filaments

Non-polar, filamentous networks made of coiled-coil dimers; provide mechanical strength and lack motor activity.

Desmosomes

Cell–cell junctions that anchor intermediate filaments and provide strong adhesion.

Hemidesmosomes

Cell–substrate junctions attaching cells to the ECM via integrins and IFs.