Chapter 14 C (Cell Bio)

Plant cells

Intermediate filaments are found in all kinds of eukaryotic cells except

____.

Monomers called intermediate filament proteins

What are intermediate filaments composed of ?

Approximately 78

How many different kinds of intermediate filament proteins are there ?

…

Steps of IF Assembly:

• Intermediate filament proteins form IF dimers:

• The IF dimers form tetramers, which are staggered tetramer of two coiled-coil dimers.

• Tetramers form lateral association of 8 tetramers, called unit-length filaments.

• The unit-length filaments are connected end to end (lengthwise) to form the intermediate filaments themselves.

Keratin filaments

Vimentin and vimentin-related filaments

Desmin

Glial fribrillary acid protein (GFAP)

Neurofilaments

Nuclear lamins

What are some examples of Intermediate filaments ?

Acidic keratin and basic keratin

What are types I and II intermediate filaments ?

Acidic keratin

found in epithelia cells, where they offer strength

Basic keratin

found in epithelia cells, where they also offer strength

Vimentin, Desmin, and GFA protein

What are types III intermediate filaments ?

Vimentin

found in lens of the eye. Maintenance of cell shape

Desmin

found in smooth muscles. Structural support

GFA protein

found in glial cells and astrocytes. For cell shape

Neurofilaments

What are types IV intermediate filaments ?

Neurofilaments

H (heavy), M (medium) and Low (L)

Lamins

What are types V intermediate filaments ?

Lamins

These form the nuclear lamina to support the nuclear membrane

Under the plasma membrane for mechanical support

Where are intermediate filaments distributed in a cell ?

Through cell junctions

How do intermediate filaments connect with the extracellular matrix ?

Through cell junctions, enabling cell adhesion

How do intermediate filaments connect with other cells ?

Stretch forces

What do intermediate filaments help cells resist ?

They are the strongest cytoskeletal structures in eukaryotic cells.

How strong are intermediate filaments ?

More stable than both microfilaments and microtubules.

How stable are intermediate filaments ?

Microtubules and microfilaments dissolve, but intermediate filaments remain in their original shape.

What happens when cells are treated with salt solutions and non-ionic detergents ?

Hair

Nails and claws

Horns and beaks

Turtle shells and feathers

Outermost layer of the skin

What structures contain keratin ?

Nuclear lamins

_____ form a meshwork of fibers that support the nuclear envelope.

Disassembly and reassembly of the nuclear lamina are controlled by phosphorylation and dephosphorylation of lamins.

How is the stability of nuclear lamins controlled ?

Certain types of progeria, or premature aging of babies.

What can defects in nuclear lamins be associated with ?

Give mechanical strength to cells

Enable cells to withstand tension forces

Strengthen the nuclear membrane

What are the three main functions of intermediate filaments ?