Difference Between Microtubules and Microfilaments

Main Difference

The main difference between microtubules and microfilaments is that microtubules are formed of tubulin protein units and normally are long, and hollow cylinders, whereas microfilaments are produced by actin proteins, and usually are double-stranded helical polymers.

Microtubules vs. Microfilaments

Microtubules are structurally helical lattice, whereas microfilaments are a double helix. Microtubules are 24 nm in diameter while microfilaments are 7 nm in diameter. Alpha and beta subunits of tubulin protein made microtubules; on the other hand, microfilaments are mainly composed of a contractile protein called actin protein. Microtubules resist bending forces and are stiff in strength; on the contrary, microfilaments are relatively strong and flexible and resist filament fracture by tensile forces and resist buckling due to compressive forces. Microtubules help plant cells in performing their proper functioning like various cell transportation purposes and mitosis; on the contrary, microfilaments help plant cells to move. Associated proteins regulating the dynamics of microtubules are MAPs, +TIPs, and motor proteins; conversely, proteins involved in the regulation of the dynamics of microfilaments are filament cross-linkers, actin monomer-binding proteins, actin-related protein 2/3 (Arp2/3) complex, and filament-severing proteins. Microtubules occur in basal bodies, cilia/flagella, centrioles, astral rays, and spindle fibers; on the flip side, microfilaments occur at the interphase of plasma gel-plasma sol and below cell membrane. A single microtubule contains 13 proto-filaments; conversely, microfilaments are structurally solid.

Comparison Chart

MicrotubulesMicrofilaments
The polymers of tubulin protein that form the part of the cytoskeleton and gives shape and structure to plant cell are microtubules.Also called actin filaments that form the part of the cytoskeleton and are present in the cytoplasm of eukaryotic cells composed of polymers of actin are microfilaments.
Structure
Helical latticeDouble-helix
Diameter
24 nm7 nm
Composition
Composed of alpha and beta subunits of tubulin proteinComposed of a contractile protein called actin protein
Strength
Resist bending forces and are stiff in strengthRelatively strong and flexible and resist filament fracture by tensile forces and resist buckling due to compressive forces
Functions
Help plant cells in proper functioning such as mitosis and various cell transport functionsHelp plant cells to move
Associated Proteins
MAPs, +TIPs, and motor proteinsFilament cross-linkers, actin monomer-binding proteins, actin-related protein 2/3 (Arp2/3) complex, and filament-severing proteins
Occurrence
In basal bodies, cilia/flagella, centrioles, astral rays, and spindle fibersAt the interphase of plasma gel-plasma sol and below the cell membrane

What are Microtubules?

The polymers of tubulin protein that form the part of the cytoskeleton and gives shape and structure to plant cell are microtubules. Microtubules are 24 nm in diameter. Alpha and beta subunits of tubulin protein made microtubules. Microtubules allow cellular transport along with motor proteins and are capable of generating forces by contracting. Actin filaments and the microtubules offer an internal structure to the cytoskeleton and make cytoskeleton to alter its shape while moving. A particular microtubule consists of thirteen proto-filaments. Actin filaments are marked with red dye, while microtubules are marked with green dye, and nuclei are marked in blue dye. Microtubules form a spindle apparatus by involving in the chromosomal segregation during meiosis and mitosis. Microtubules are nucleated in the centromere which is the MTOCs (microtubule organizing centers) to form the spindle apparatus. Microtubules occur in basal bodies, cilia/flagella, centrioles, astral rays, and spindle fibers. Microtubules resist bending forces and are stiff in strength, and they allow gene regulation of transcription factors through specific expressions. They control the cell structure in the plant body. They also provide conveyance for various vesicles having important materials to the rest of the cell. Associated proteins regulating the dynamics of microtubules are MAPs, +TIPs, and motor proteins.

What are Microfilaments?

Also called actin filaments that form the part of the cytoskeleton and are present in the cytoplasm of eukaryotic cells composed of polymers of actin are microfilaments. Microfilaments are almost 7 nm in distance with a coil of double-helix that recaps after every 37 nm. Microfilaments are mainly made up of contractile protein which is called as actin protein and two strands in a helical structure. Microfilaments are considered as the highest fibers present in the cytoskeleton. Microfilaments are involved in cell motility like amoeboid movement and cytokinesis. Normally microfilaments play a vital role in cell contractility, cell shape, mechanical stability, endocytosis, and exocytosis. In muscle cells, actin filaments are associated, and myosin proteins produce forces to backing muscle contraction on the filaments. Microfilaments are relatively strong and flexible and resist filament fracture by tensile forces and resist buckling due to compressive forces. Proteins presents in the maintenance of the changing aspects of microfilaments are filament cross-linkers, actin monomer-binding proteins, actin-related protein 2/3 (Arp2/3) complex, filament-severing proteins, filament-end tracking protein, filament barbed-end cappers like CapG, and depolymerizing actin proteins. Microfilaments occur at the interphase of plasma gel-plasma sol and below cell membrane, and they are structurally solid.

Key Differences

  1. Microtubules are structurally helical lattice, whereas microfilaments are a double helix.
  2. Microtubules are 24 nm in diameter while microfilaments are 7 nm in diameter.
  3. The tubulin protein subunits alpha and beta made of microtubules; on the other hand, the contractile protein which is known as actin protein mainly produce microfilaments.
  4. Microtubules resist bending forces and are stiff in strength; on the contrary, microfilaments are relatively strong and flexible and resist filament fracture by tensile forces and resist buckling due to compressive forces.
  5. Microtubules help plant cells in performing their proper functioning like various cell transportation purposes and mitosis; on the contrary, microfilaments help plant cells to move.
  6. Associated proteins regulating the dynamics of microtubules are MAPs, +TIPs, and motor proteins; conversely, proteins involved in the regulation of the dynamics of microfilaments are filament cross-linkers, actin monomer-binding proteins, actin-related protein 2/3 (Arp2/3) complex, and filament-severing proteins.
  7. Microtubules occur in basal bodies, cilia/flagella, centrioles, astral rays, and spindle fibers; on the flip side, microfilaments occur at the interphase of plasma gel-plasma sol and below cell membrane.
  8. A single microtubule contains 13 proto-filaments; conversely, microfilaments are structurally solid.

Conclusion

Above discussion concludes that microtubules are made up of tubulin proteins, long, and hollow cylinders, whereas microfilaments are made up of actin proteins, and are double-stranded helical polymers.

Janet White

Janet White is a writer and blogger for Difference Wiki since 2015. She has a master's degree in science and medical journalism from Boston University. Apart from work, she enjoys exercising, reading, and spending time with her friends and family. Connect with her on Twitter @Janet__White

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