Section 7.6 Cell Systems III: The Dynamic Cytoskeleton

The cytoskeleton is not a

static structure

fibrous proteins in cytoskeleton

move and change

movement of fibrous proteins in Cytoskeleton

Alter the cell’s shape, Shift its contents, and Even move the cell itself

Three types of cytoskeletal elements:

Actin filaments (microfilaments)

Intermediate filaments

Microtubules

Actin filaments or microfilaments

Smallest; Polymerization of individual actin molecules into long coiled strands

Plus (grows fast) and minus (grows slow) ends

Actin filaments

how are Actin filaments grouped

long bundles or dense networks

where are Actin filaments found

inside the plasma membrane

Use ATP to change shape and do work:

Actin filaments

Cell crawling

actin filaments growing in one direction, moving the cell

Use ATP to change shape and do work actin filaments

Muscle contraction

Cytokinesis

Cytoplasmic streaming

Intermediate filaments Many types:

each consisting of different proteins

what does the Intermediate filaments provide

structural support

the Intermediate filaments has no

movement

Nuclear lamins are

intermediate filaments

what Give the nucleus its shape

Intermediate filaments

Intermediate filaments forms

dense mesh under the nuclear envelope

Intermediate filaments Anchor

chromosomes

Intermediate filaments Break up and reassemble

nuclear envelope when cells divide

Largest cytoskeletal elements

Microtubules

Microtubules

Large, hollow tubes made of tubulin dimers

Microtubules have two

polypeptides, called α-tubulin and β-tubulin

Microtubules has a

polarity, dynamic

where does a Microtubules grow from

plus ends

Microtubules Originate from the

microtubule organizing center

Microtubules Plus ends grow

outward

what Radiating throughout the cell

Microtubules

centrosome

animal cells, this center is called

It contains two bundles of microtubules

centrioles

Microtubules Serve as Tracks for

Vesicle Transport

Microtubules Provide

stability, structural framework for organelles

involved in movement

Microtubules

Microtubules parate

chromosomes during cell division

Serve as “railroad tracks” for vesicle transport

Microtubules