The Cytoskeleton and Connections Between Cells (September 4th)

Functions of the Cytoskeleton

Structure and Support

Intracellular transport

Contraction and Motility

Spatial Organization

What are the Major Filamentous Structures that make up the Cytoskeleton?

Microtubules

Actin filaments (or microfilaments)

Intermediate Filaments

Which Major Filamentous Structures are found in all Eukaryotes?

Microtubules and Actin filaments (or microfilaments)

Which Major Filamentous Structure is not found in all Eukaryotes (not usually in animals with cytoskeletons)

The Intermediate Filaments

What is critical in the structure/ function of filamentous structures?

Accessory proteins (including motor proteins)

Microtubules

Polarity and a rigid structure

Primary function is to support, intracellular transport, cell organization (positioning organelles with cytosol, and movement of the DNA during cell division)

Make up Flagella and Cilia

Made up of two different molecules: Alpha and Beta tubulin

Non-covalent bonding allows growth and shrinkage

Actin Filaments

Has polarity and a flexible filament

Primary function is shape, motility, and contraction

Non-covalent bonds allow growth and shrinkage

Moves cell by breaking itself down into largest moveable pieces, rearranging itself and then reassembling and pushing the membrane forward, or pulling it back

Intermediate Filaments

Made up of various proteins with no polarity

Structure is tough and rope-like so primary function is strength and support

Ex, is keratin in fingernails, hair, skin cells: Acidic and basic keratin are found in equal concentrations in the aforementioned rope

Function of the Cytoskeleton: Intracellular Transport

Accomplished by Actin Filaments and Microtubules

Use Motor Proteins

Motor Proteins with Microtubules Ex. is flagella/cilia movement. The A filament slides over the B filament causing whipping motion

Motor Proteins with Actin Filaments is defined by a walking motion. Ex. is muscle contraction

Extracellular Matrix

Material on the outside of the cell that accomplish things for the cell. Mostly Glycoproteins (Proteins that have been Glycosylated i.e. Collagen)

Extracellular Matrix accomplishes:

Supporting

Adhesion

Movements

Regulation

What are cells binding to?

Other cells

Membranes

Channel forming junctions (using Desmosomes)

The Plasma Desmata performs the …. function in plants which allows it to move material between cells.

Gap Junction

Flagella

A long and hair-like structure that allows the cell to move

Cilia

One of many small hair-like cells that move entire cells or substances along a cell’s outer surface

Gap Junction

A channel between two adjacent animal cells that allow ions, nutrients, and low molecular weight substances to pass between cells, enabling communication

An example of microtubules using motor proteins is:

The flagella or cilia movements

An example of Actin Filaments using motor protiens is:

The ‘walking motion’ of myesin ‘walking’ over actin filaments in muscle contractions

What is the use of a ‘tight junction’?

Prevents materials from moving between cells