Bio 178 Lecture 9Cell Structure

Copyright: E.G. Platzer

Reading

• Chapter 5

Quiz Material

• Questions on P 104

• Chapter 5 Quiz on Text Website (www.mhhe.com/raven7)

Outline

• Eukaryotic Cells (Cntd)1. Cytoskeleton (Cntd.)

The Cytoskeleton

The Cytoskeleton

Intermediate Filaments

Microtubules Actin Filaments

http://www.tmd.ac.jp/artsci/biol/textbook/cellmove.htm

Actin Filaments in Melanoma Cell

http://cellix.imolbio.oeaw.ac.at/Videotour/video_tour_5.html

MicrotubulesSize~ 25 nm diam

Composition

• Hollow tubes - 13 protofilaments.

• Each subunit - tubulin heterodimer of - and - tubulin monomers.

http://www.tmd.ac.jp/artsci/biol/textbook/cellmove.htm

Microtubules

Functions

• Movement of organelles

• Chromosome movement

Microtubules in Fish Fibroblast Cell

http://cellix.imolbio.oeaw.ac.at/Videotour/video_tour_12.html

Cy tubulin growing into adhesion sites

Intermediate Filaments

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/Cytoskeleton.html

Intermediate FilamentsSize8-10 nm

CompositionRopes of a heterogeneous mix of fibrous proteins (eg. vimentin, keratin)

Intermediate Filaments

Stability

Post-formation do not usually break down.

Functions

Support

Centrioles

Centrosome• The primary microtubule organizing center of animals and acts as the spindle pole during mitosis.

• Usually contains a pair of centrioles.

• Located near nucleus.

Structure• Not membrane-bound.

• 9 triplets of microtubules.

“The centrosome is the main microtubule organizing center (MTOC) of the cell. It is composed of two orthogonally arranged centrioles surrounded by an amorphous mass of pericentriolar material (PCM)”.

http://en.wikipedia.org/wiki/Centrosome

The Centriole

The Centriole (cntd)

KingdomsAnimals and some protists

Functions

• Microtubule assembly

• Anchor of cilia and flagella (basal bodies)

http://www-cteu.u-bourgogne.fr/cav/dicobio/fiches/centriole.html

Dynein

Molecular MotorsDescription• Proteins that transport organelles, chromosomes, and vesicles using the cytoskeleton as a “highway”.

• Use ATP for energy.

Motor Types• Differ in the type of filament they bind to, cargo they carry, and directionality.

• Examples - Dynein, kinesin, myosin.

Directionality of Kinesins & Dyneins

http://www.tmd.ac.jp/artsci/biol/textbook/cellmove.htm

Muscle – Actin & Myosin

http://www.tmd.ac.jp/artsci/biol/textbook/cellmove.htm

Myosin and Actin Video

Alberts et al.: Molecular Biology of the Cell, 16.8