Microfilaments vs. Microtubules

Microfilaments and microtubules are key components of the cytoskeleton in eukaryotic cells. A cytoskeleton provides structure to the cell and connects to every part of the cell membrane and every organelle. Microtubules and microfilaments together allow the cell to hold its shape, and move itself and its organelles.

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Microfilaments

Microtubules

Structure Double Helix Helical lattice
Size 7 nm in diameter 20-25 nm in diameter
Composition Predominantly composed of contractile protein called actin. Composed of subunits of protein tubulin. These subunits are termed as alpha and beta.
Strength Flexible and relatively strong. Resist buckling due to compressive forces and filament fracture by tensile forces. Stiff and resist bending forces.
Function Micro-filaments are smaller and thinner and mostly help cells move Microtubules are shaped similarly but are larger, and help with cell functions such as mitosis and various cell transport functions.

Contents: Microfilaments vs Microtubules

Fluorescence double staining of a fibroblast. Red: Vinculin; and Green: Actin, the individual subunit of microfilament.
Fluorescence double staining of a fibroblast. Red: Vinculin; and Green: Actin, the individual subunit of microfilament.

edit Formation and Structure

Microtubules constructed from alpha and beta tubulin
Microtubules constructed from alpha and beta tubulin

edit Structure of Microtubules

Actin, the individual subunit of Microfilament
Actin, the individual subunit of Microfilament

Microtubules are composed of globular proteins called tubulin. Tubulin molecules are bead like structures. They form heterodimers of alpha and beta tubulin. A protofilament is a linear row of tubulin dimers. 12-17 protofilaments associate laterally to form a regular helical lattice.

edit Formation of Microfilaments

Individual subunits of microfilaments are known as globular actin (G-actin). G-actin subunits assemble into long filamentous polymers called F-actin. Two parallel F-actin strands must rotate 166 degrees to layer correctly on top of each other to form the double helix structure of microfilaments. Microfilaments measure approximately 7 nm in diameter with a loop of the helix repeating every 37 nm.

edit Biological Role of Microtubules and Microfilaments

edit Functions of Microfilaments

edit Functions of Microtubules

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