Cytoskeleton

The cyctoskeleton directs movement of things inside the cell such as:

  • Mucsle contraction
  • Cell division
  • Cytoplasmic streaming

The cytoskeleton allows the cell to move the membrane

Parts of the cell that move because of the cytoskeleton are white blood cells, engulfing bacteria and amoeba movement

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Types of cytoskeleton

The intermediate filaments are 10 nanometers in diameter and locate throughout the cytoplasm and nucleus

  • intermediate filaments form along a rope like strands of stacked twisted protein

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 filaments form along rope-like strands into twisted proteins

Intermediate filaments protect from mechanical stress

  • The nucleus is surrounded and supported by the nuclear lamina

\ The microtubules (25 nanometers diameters) are localized from a primary location to reach many parts of the cell

\ \ The actin aka microfilaments (7 nanometers in diameter) are localized throughout the cell but concentrated along the cell periphery and in processes

\ Actin assembly drives through a treadmill

Monomers assemble into a strand as ATP bounds actin binds to the growing strand

 

Actin hydrolyzes ATP to ADP reducing binding affinity for other actin

high monomer concentration drives assembly at both ends

ADP bound actin disassembles

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Actin supports cell movement

Actin assembly pushes the cell membrane into long protrusions like to lamellipodia

\ Actin filaments formation drives the membrane forward by interaction proteins on the membrane

\ Actin filaments interact with adhesion molecules to attach membrane to the substrate

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Cell Movement

Cell movement in the microtubules

Microtubules have directionality with a plus and minus end

Tubulin isoforms assemble to form filament

  • alpha and beta dimers form filament
  • gamma forms a stable base
Microtubules assembly is governed by dynamic instability

GTP bound alpha/beta dimers to assemble onto growing + end of microtubules

The alpha and beta dimers naturally hydrolyze GTP to GDP

GDP bound alpha/beta dimers interactions are not as strong as GTP bound dimers

Adding materials can only be added from oneside because one side is located by the gamma rays

Microtubules collapse is called catastrophe

Microtubules are used to transport cargo vesicles around the cell

When a vesicle travels throughout the cell, the microtubules are laid like train tracks and the vesicles follow along the microtubules’ lines

\ Protein filled vesicles travel along the microtubules too

 

Cell Divison

 

Actin and microtubules interact in cell polarity