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Cytoskeleton Component Explorer

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About This MicroSim

This interactive diagram compares the three major cytoskeletal filament types side by side: microfilaments (actin), microtubules (tubulin), and intermediate filaments (keratin, lamin, etc.). All 15 labeled structures include subunit composition, cross-section views, and motor proteins.

How to Use

  • Explore mode: Hover over any numbered marker or label to see a description of that structure, its function, and AP exam tips.
  • Quiz mode: Click the Quiz button to test your knowledge. Labels are hidden — click the correct marker when prompted.
  • Edit mode: Open main.html?edit=true to calibrate marker positions by dragging.

Structures in This Diagram

Microfilaments (Actin) — ~7 nm

  1. Actin filament (F-actin) — Double helix of G-actin monomers
  2. G-actin monomer — Globular subunit, binds ATP
  3. Plus end — Fast-growing barbed end
  4. Minus end — Slow-growing pointed end
  5. Cross-section — Two-strand profile, thinnest filament

Microtubules — ~25 nm

  1. Microtubule — Hollow cylinder of 13 protofilaments
  2. Alpha-tubulin — Orange subunit, binds GTP (non-exchangeable)
  3. Beta-tubulin — Blue subunit, binds GTP (hydrolyzable)
  4. Cross-section — Ring of 13 protofilaments, hollow lumen
  5. Kinesin — Plus-end motor, anterograde transport
  6. Dynein — Minus-end motor, retrograde transport

Intermediate Filaments — ~10 nm

  1. Intermediate filament — Rope-like, non-polar, tensile strength
  2. Coiled-coil dimer — Two alpha-helices wound together
  3. Cross-section — Dense solid core, no lumen
  4. Keratin filaments — Epithelial cell network, connects to desmosomes

Size Comparison

Filament Type Diameter Monomer Polarity Motor Proteins
Microfilament ~7 nm G-actin (ATP) Yes (+/−) Myosin
Microtubule ~25 nm α/β-tubulin (GTP) Yes (+/−) Kinesin, Dynein
Intermediate filament ~10 nm Varies (keratin, lamin, etc.) No None

Iframe Embed Code

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